PDA

View Full Version : SWG Operation - Lessons Learned



Pages : [1] 2

PatL34
05-08-2006, 10:22 PM
Having operated a SWCG pool since May of 1998, I thought I would give my dollarsworth :) of SWCG experience over the years, especially for the new SWCG owners on the forum..

Living in Central Florida allows me to run the Diamondbrite 20,000 gallon pool 8 - 12 hours a day depending on use and water temperature. The SWCG was initially an AutoPilot LS1000 with a R-15 cell. It was upgraded with a Pool Pilot DIG-220 and an SC-48 cell about 2 years ago when the R-15 cell started to die.

I had to replace the R-15 once only, and am still running quite happily on the SC-48 cell.

SWCG Operation

I had previously described in the old forum (now lost) how the cell creates the products needed to sanitize the pool and am resurrecting that procedure, with some additional explanations. There are some corrections since this was originally created, and I have to thank Chem_Geek for bringing them to light.

Salt water passing through the cell is dissociated using DC electricity applied to the membranes in the cell. This creates

Hydrogen gas, H2
Chlorine gas, Cl2

The Chlorine gas reacts with the pool water to make Hypochlorous Acid, which is the component that destroys the bacteria and chloramines in the pool.

Cl2 + H2O --> HOCL +H+ + Cl-

The Hypochlorous Acid further dissociates into Hydrogen ions and Hypochlorite ions.

HOCl <--> H+ + OCl-

As this reaction can go both ways, it depends on the pH. The higher the pH , the further it goes to the right or more dissociation. The lower the pH, the more it goes to the left, creating more Hypochlorous Acid, and making it more effective as a sanitizer.

This is why you need to keep the pH between 7.2 - 7.6 for best sanitization.

To summarize then for the non-chemists, the cell creates the components mentioned at the beginning, reacting to make Hypochlorous Acid, the main sanitizing agent. The chloramines are instantly destroyed, leaving only nitrogen and hydrogen coming from the returns, and retaining chlorine for use in the pool because of the high CYA content.

Lessons Learned

pH - Maintain between 7.2-7.6 using muriatic acid. Most of the other manufacturers also recommend this pH range. If you decide to use dry acid, then you will have to add salt to maintain the salt level. The effect of dry acid is to raise the TDS level as well as lower the pH and is not part of the process. I prefer to keep it simple with Muriatic Acid.

Salt Level - Different manufacturers call for different salt levels for their products. The Poolpilot calls for 2500 - 3500 ppm, Watermaid for 6000 ppm, and Aquarite from 2700 - 3400 ppm. For the Poolpilot, maintaining 3000 - 3500 ppm seems to work fine for me.

BTW, when adding salt in granular form to a plaster pool that has a concrete coping, be very careful not to spill any salt granules on the concrete. It will eventually create a hard deposit that will have to be removed with hammer and chisel. Wash any areas with pool water using a bucket back into the pool or use a garden hose.

Flow through the Cell - Several factors can reduce the flow through the cell, such as high differential pressure through the filter, which may need to be cleaned or backwashed. The use of solar or other forms of heating too can have an effect, as can vacuuming. With the Autopilot or Poolpilot, there is a springloaded check valve that helps to maintain flow through the cell at low flows. Other factors are scale buildup on the trisensor affecting both flow and salt concentration. This requires cleaning the unit with dilute Muriatic acid, even though the cell might not have scale. Whenever I clean the cell the trisensor is included. I use a Muriatic acid concentration of 1 part acid to 4 parts water. Always add the acid to the water, never the other way round.

Calcium Hardness - Keeping the CH at no more than 300 ppm for a plaster pool helps to keep the cell clear of scale. Check the cell once a month for any scale buildup, and clean according to the manufacturer's instructions, or the method mentioned above. A vinyl pool has to have no more than 120 ppm, but this may be different for other types of non-plaster pools.

Refill Water - Use of softened city water as refill helps to minimize the buildup of calcium hardness as well. Use of well water especially in Central Florida should be avoided, as if it contains Hydrogen Sulfide gas, it can destroy the active coating on the cell fairly rapidly. If it has to be used, either find a way to bypass the cell, or shut the circulation down while refilling to allow the gas to escape. A further help would be to use a filter that can remove iron, as this a major problem here in Central Florida.

Stabilizer (CYA) - Most of the manufacturers recommend 60 - 80 ppm, but I have been able to run with nearly 0 ppm in winter to about 50 ppm in the summer, with a maximum of 60 ppm. These figures have worked for me, but some units may require more. The reason the manufacturers require a high CYA concentration is because the cell produces a high concentration of chlorine at the cell membranes, and most of it is used in instantly destroying the chloramines. By keeping the CYA level high, it maintains the chlorine needed in the body of the pool.

Testing - Having a very good testkit is paramount for checking SWCG operation. Besides the regular chemicals to be tested, a drop type testkit for salt is highly recommended as a backup for pH meters. These units have to be calibrated frequently for reliable operation, no matter who tells you different. Ben's PS234 testkit is the choice of record for this in my opinion. Test strips should ONLY be used if there is nothing else, and are not recommended for SWC or regular bleach operation in my opinion.

Startup and Upsets - If the pool system has to be shut down for the winter, then on Spring startup, it is my recommendation and the manufacturer's not to turn on the SWCG until the system has been stabilized using bleach, and only bleach, as well as the other chemicals including salt to the manufacturer's specifications.

Similarly for upsets, there is no need to increase the SWCG loading, as this reduces cell life unnecessarily. Add bleach as needed to bring the sanitization level back to normal for your system. The SWCG is designed to maintain a steady chlorine level only, provided the water chemistry is monitored frequently.

For a new plaster pool, some plaster vendors recommended not adding salt for a SWCG for at least a month, until the plaster has had time to cure. Most of the time the salt can be added straightaway.

Also make sure that all leaves and debris are removed from the pool, skimmers and pool pump basket on a regular basis, otherwise the cell is working longer to remove this debris.

Cable Connections - need to be checked both to the cell and control sensors for good electrical contact on a regular basis, as this seems to be the weakest area when a control unit is not functioning properly. Scaling of the sensors can be another problem and have to be checked if there is scale buildup on the cell.

Pros

The unit saves having to lug Liquid Chlorine or Bleach and pucks, which have to be kept in a cool environment tightly sealed.

The great advantage is that it is a constant source of Chlorine, assuming the rest of the pool chemistry is maintained properly.

Cost wise I have found it is equivalent to running a 220 watt bulb for whatever hours of the day the unit is running. Based on the PoolPilot I have, it is about $22 per month for an 8 - 12 hour day, and that includes the cost of the cell over a 5 year life.

As the price of oil goes up, so will the cost of electricity and the cost of manufacturing bleach. SWCGs will start to pay for themselves in the long run. The initial cost will offset any price increases in bleach later on.

Cons

According to most AG pool manufacturers, they are not recommending these units for their pools and you will have to check the warranty. Similarly, SWCG manufacturers are not recommending them for AG pools and will give fair warning if you do. Check with both types of manufacturer bofore investing in an AG pool/SWCG combination.

The initial cost can be the problem here, but once set up and running, the return in ease of maintenance will be well worthwhile. Prices from pool equipment suppliers on the Internet give you a lot more choices for shopping around for the best and lowest prices.

I have found no real problems other than cable and sensor connections. Electricity has a way of finding the weakness in any electrical circuit.

-----------------------------------------

Any input from the "seasoned" SWCG owners would be appreciated, including manufacturer's reps.

I did this mainly as a general explanation for the new SWCG owners, to help them operate their particular setup.

Hope this all helps.

Pat

gwrace1
05-08-2006, 10:48 PM
I started up a new 26000 gallon pool in March of this year with an Aquarite SWG. I have been able to maintain chlorine levels by running our 2 speed pump on low for about 12 hours per day at night. The SWG is set at 40% with a salt level of 3500 PPM. The only adjustments I've needed to make are for PH. It takes a dose of Muriatic Acid about once per week. I am currently running approximately 35-40 PPM stabilizer and maintaining a FC of 4PPM. The water has been crystal clear since startup and I have never shocked the pool.

My only water source was iron rich well water. To deal with the metals I placed an iron removing 2 micron whole house filter ahead of the softener and used softened water to fill the pool. It took 5 days and many regeneration cycles to complete the process. While the pool was filling I added a metal out product and Polyquat 60%. Once the pump and filter were working I allowed this mixture to circulate for several days with the SWG off. I'm using Zeobest filter media in a 26" Pentair sand filter on a two speed pump. No bleach or chlorine was added to the pool.

Day 4 I switched on the Aquarite and gave it a few days to bring up the chlorine levels. Once that was done I added stabilizer via the skimmer to the 35-40 PPM level. The pool has been simple to maintain ever since.

A quality test kit with salt level is a must.

tonyl
05-09-2006, 09:24 AM
Thanks Pat,
That's a great post. I remember vaguely the lost version so I printed this new one. Chemistry isn't my forte but your explanation is one that I get.

Question: When the first cell "started to die", what was the indication? The reason I'm asking is my cell output seems to go up every year with the other variables the same. I assumed (incorrectly?) that it would suddenly die.

Thanks, Tony

PatL34
05-09-2006, 12:54 PM
Thanks Pat,
That's a great post. I remember vaguely the lost version so I printed this new one. Chemistry isn't my forte but your explanation is one that I get.

Question: When the first cell "started to die", what was the indication? The reason I'm asking is my cell output seems to go up every year with the other variables the same. I assumed (incorrectly?) that it would suddenly die.

Thanks, Tony

You will find that the DC volts go up and the DC amps go down, indicating a higher resistance between the membranes as the coating wears out. The chlorine output starts to go down as well.

In your case, you appear to have a cell that seems to "rejuvenate" itself.;) I would expect that might happen if you acid wash the cell at the end of the season, but I suspect something else might be happening. It should lose efficiency as it gets to the end of its life.

Hope this helps.

Pat

Pat

tonyl
05-09-2006, 02:14 PM
Well, when I typed my output goes up I should have said output SETTING......ahhh....what a difference a word makes.

Thanks for the info Pat, I'll have to keep an eye on it.

Tony

clone1008
05-09-2006, 02:33 PM
Pat,

Very informative write-up, especially since I'm considering the conversion myself. In your "Lessons Learned", can you tell me have there been any negatives? What about corrosion over an extended period of time? Any long term damage to the tile grout or coping? I'm just a little leary after getting caught up in the "Baquicil Movement" about 7 years ago and the horrors involved with that.

PatL34
05-09-2006, 04:55 PM
Pat,

Very informative write-up, especially since I'm considering the conversion myself. In your "Lessons Learned", can you tell me have there been any negatives? What about corrosion over an extended period of time? Any long term damage to the tile grout or coping? I'm just a little leery after getting caught up in the "Baquicil Movement" about 7 years ago and the horrors involved with that.

The only real negative I found was having to replace the powerboard on the control unit 3 times because of bad quality control on the original LS1000 unit.

Corrosion at the salt levels that the Pool Pilot I use (3000 - 3500) has not given any instances of corrosion, other than having to wash the aluminum pool rakes and attachments, which were never designed for a saltwater pool any way. If you do find corrosion to the tile grout or coping, that is evidence of bad workmanship on the part of the pool builder.

In addition, I had to add a fresh water shower to prevent my wife and her swimsuit from being corroded away.:D BTW she was a pediatric nurse and understands that salty water hurts the eyes less than fresh water.

I think you will find that SWCG operation is a far cry from Baquacil and you should find it less troublesome. Having said that make sure you keep your pool chemistry up to par, and you should have no problems.

Hope this helps in your decision.

Pat

clone1008
05-09-2006, 05:43 PM
The only real negative I found was having to replace the powerboard on the control unit 3 times because of bad quality control on the original LS1000 unit.

Corrosion at the salt levels that the Poolpilot I use (3000 - 3500) has not given any instances of corrosion, other than having to wash the aluminum pool rakes and attachments, which were never designed for a saltwater pool any way. If you do find corrosion to the tile grout or coping, that is evidence of bad workmanship on the part of the pool builder.

In addition, I had to add a fresh water shower to prevent my wife and her swimsuit from being corroded away.:D BTW she was a pediatric nurse and understands that salty water hurts the eyes less than fresh water.

I think you will find that SWG operation is a far cry from Baquacil and you should find it less troblesome. Having said that make sure you keep your pool chemistry up to par, and you should have no problems.

Hope this helps in your decision.

Pat


Pat,

Thanks for the help. You raise another interesting topic...will the salt water at that low of a level really mess up swim suits? Also, do you really feel the need to fresh water rinse in this type of water? I know the salty feeling of swimming in the Gulf but I didn't think this would be an issue in a pool. In fact most of the websites talk about the "good" feeing skin and no more bleached out suits.

Ric

PatL34
05-09-2006, 07:19 PM
Pat,

Thanks for the help. You raise another interesting topic...will the salt water at that low of a level really mess up swim suits? Also, do you really feel the need to fresh water rinse in this type of water? I know the salty feeling of swimming in the Gulf but I didn't think this would be an issue in a pool. In fact most of the websites talk about the "good" feeing skin and no more bleached out suits.

Ric

I think you were taking me too seriously. The fresh water shower is more a convenience to remove the salt from the body and suit, before going in and taking a regular shower. Even public pools without salt have showers for this purpose. And yes you do have "good' feeling skin in a salt water pool, probably better than in the sea.

But even when swimming in the Gulf, the salt content is 3 - 4 times higher than in a salt water pool, but you still take a fresh water shower to remove the sea salt. Sea water to my knowledge has never ruined a swimsuit.

Hope this clears things up.

Pat

clone1008
05-09-2006, 07:27 PM
I think you were taking me too seriously. The fresh water shower is more a convenience to remove the salt from the body and suit, before going in and taking a regular shower. Even public pools without salt have showers for this purpose. And yes you do have "good' feeling skin in a salt water pool, probably better than in the sea.

But even when swimming in the Gulf, the salt content is 3 - 4 times higher than in a salt water pool, but you still take a fresh water shower to remove the sea salt. Sea water to my knowledge has never ruined a swimsuit.

Hope this clears things up.

Pat

Point well taken...and thanks for the hygene tips...LOL...just kidding...thanks for all the info you've been very helpful!

Ric

salinda
05-10-2006, 01:32 PM
Can you tell me what drop-type salt test I should use? I have been using the strips that you put in a small vial of water and wait a few minutes to take a reading.

Also, regarding the potential damage to tile/coping etc., I have found only the opposite. I have a Calcium reading on the high side (520 ppm). My overflow from my spa always had a lot of scale. Since the swg has been in operation, the scale has actually been disappearing. Maybe I am just more aware of ph and adding muriatic acid more often.

I do use A LOT of acid--at least 1/2 gallon/week with a 37,000 gallon pool.

PatL34
05-10-2006, 03:27 PM
Can you tell me what drop-type salt test I should use? I have been using the strips that you put in a small vial of water and wait a few minutes to take a reading.

Also, regarding the potential damage to tile/coping etc., I have found only the opposite. I have a Calcium reading on the high side (520 ppm). My overflow from my spa always had a lot of scale. Since the swg has been in operation, the scale has actually been disappearing. Maybe I am just more aware of ph and adding muriatic acid more often.

I do use A LOT of acid--at least 1/2 gallon/week with a 37,000 gallon pool.

The salt water test kit is from Taylor, (Item # K-1766) which you can order from your local pool store. I don't think Taylor likes to sell to the public direct. Test your salt level at least once a week while removing the scale and then once a month when your pool chemistry is balanced. Use the salt test strips only as a rough guide.

A calcium reading of 520 ppm is definitely on the high side, so keeping the pH down to between 7.2 to 7.6 will definitely help. You will be using a lot of acid during this time. 300 ppm CH is your goal. The TA should be checked as well, and if above 150 ppm, I would start aerating to bring it down using a low pH down to 120 ppm. Hopefully your scale should disappear even faster.

Check your cell once a month too.

Hope this helps.

Pat

salinda
05-10-2006, 03:41 PM
Pat, I have very little scaling now--less since the swg was installed (not what I expected, but it's great!). My TA is only 90 according to the PS233. My system is well-balanced except for the Ca level and that is the same as last fall when I closed. The cell on my Clearwater is clear so I visibly check it often and I did do a muriatic acid soak on it at the beginning of this spring. Why would the salt level change "while removing scale?" I had to adjust my salt level this spring because we got soaked this winter in California and my water was very diluted, but now we won't see rain until next fall so the salt level should be fixed.

Doesn't the salt water test use silver, which is expensive? That's probably why they don't have too many in stock.

PatL34
05-10-2006, 06:27 PM
Pat, I have very little scaling now--less since the swg was installed (not what I expected, but it's great!). My TA is only 90 according to the PS233. My system is well-balanced except for the Ca level and that is the same as last fall when I closed. The cell on my Clearwater is clear so I visibly check it often and I did do a muriatic acid soak on it at the beginning of this spring. Why would the salt level change "while removing scale?" I had to adjust my salt level this spring because we got soaked this winter in California and my water was very diluted, but now we won't see rain until next fall so the salt level should be fixed.

Doesn't the salt water test use silver, which is expensive? That's probably why they don't have too many in stock.

You might have had some scale on the salt sensor which is now clearing up.
You should be able to get the salt water test kit easily. The chemical used is silver nitrate. This reacts with potassium dichromate indicator to give the red color of potassium nitrate.

The reason they don't have too many in stock, is that the test kit at $25, lasts a LOT longer than the test strips at about $8.00, a third of the price. They would rather you buy test strips.:mad:

Hope this helps.

Pat

PoolDoc
05-11-2006, 09:04 AM
You might have had some scale on the salt sensor which is now clearing up.
You should be able to get the salt water test kit easily. The chemical used is silver nitrate. This reacts with potassium dichromate indicator to give the red color of potassium nitrate.

The reason they don't have too many in stock, is that the test kit lasts a LOT longer than the test strips at about a third the price, about $8.00.
Pat

Hi Pat,

It looks like you've created a thread worth making a 'sticky', but it's a bit cluttered with followup OT items. If you would, post a copy again, and then PM me when you have done. I'll add a 'threatening' follow-on ;), asking people who know (including Sean & Mark) to offer corrections. Once corrected (something I can't do, never having had a SWG), I'll 'sticky' it.

Oh, and about the K-1766 -- were you really able to get one for $8? It currently lists for $20.75, and I thought I was offering a real deal on the PS234S. But, if you can get one for $8, it's not a deal. AgNO3 prices *are* way up, so it's possible that the older price was much lower -- I haven't looked through old Taylor price lists. And, a very quick 'Google' for K-1766 showed prices between $24 and $35.

Ben

PatL34
05-11-2006, 09:13 AM
Hi Pat,

It looks like you've created a thread worth making a 'sticky', but it's a bit cluttered with followup OT items. If you would, post a copy again, and then PM me when you have done. I'll add a 'threatening' follow-on ;), asking people who know (including Sean & Mark) to offer corrections. Once corrected (something I can't do, never having had a SWG), I'll 'sticky' it.

Oh, and about the K-1766 -- were you really able to get one for $8? It currently lists for $20.75, and I thought I was offering a real deal on the PS234S. But, if you can get one for $8, it's not a deal. AgNO3 prices *are* way up, so it's possible that the older price was much lower -- I haven't looked through old Taylor price lists. And, a very quick 'Google' for K-1766 showed prices between $24 and $35.

Ben

Ben,

Thanks for your support. I will "clean it up" so to speak and resubmit it. I was trying to make it as generic as possible.

Regarding the K-1766 testkit, it is the test strips that I meant were at $8. My apologies for the confusion, and I will edit that post to make it clearer. My kit cost $23 over a year ago.

Thanks again.

Pat

sw_stupid
06-16-2006, 12:36 PM
Just trying to keep this at the top so we can have a sticky. Has this already been saved as a sticky somewhere? I can't find it.

sw_stupid
06-16-2006, 12:39 PM
So Pat, does this mean I need to maintain pH a LITTLE low (7.4 maybe) to make the SWC more effective? I am looking for a way to cut down how long the SWC generates (it's at 75% now). It sounds like a lower pH might help. I maintain 7.8 now.
Thanks,
Brad

PatL34
06-16-2006, 01:02 PM
Brad,

7.8 pH is generally considered to be the high end where chlorine production by the cell is minimal. 7.4 would be ideal, and will help to reduce the loading on the cell, and the %age setting.

Depending on your system, if you can keep a fairly steady pH with muriatic acid, and the TA at 100 - 120 ppm, you should have more time for swimming.

Pat

PS. It is not yet a sticky and am waiting to hear from Ben regarding this.

boscogabby
06-16-2006, 08:18 PM
Very helpful thread. I have an Aquarite SWCG and I have a PH of 7.4 and TA of 120 which I am able to maintain pretty consistently without adding acid. However I am reading alot in this thread about adding acid to maintain PH. Is this because most of these pools are plaster and not vinyl? I have an inground 12,000 gallon vinyl pool. Filter runs 12hrs a day and SWCG at 20%.

PatL34
06-16-2006, 10:38 PM
I came across this anomaly in another thread in this forum I think and have not yet been able to find a reason for the steady pH in vinyl pools.

If you could post a complete analysis, and mention the chemicals you add on a regular basis, it might help to get a better insight. Also what you do when there is an upset through bather load, weather conditions, etc.

Pat

cwstnsko
06-16-2006, 11:59 PM
The 1st thing you need to know to understand stability or lack therof is the chemistry of your make-up water. My make up water comes out of the tap above 7.8 and that's part of the reason I add acid on a regular basis. My pebble sheen is still less than 2 years old, so it may still be driving the PH up as well. I use about 2 gallons of acid a month in a 14,000 IG pool

waterbear
06-17-2006, 12:45 AM
I have a fiberglass pool, my fill water has a pH of 7.2 and an TA of 110. My pool also has TA of 110. I have to add acid every 3 weeks to get my pH to 7.2. After 3 weeks it goes up to 7.6 or slightly higher and I add acid again. Run my cell at 5% output with 8 hours of run time to maintain 3ppm FC. Still a small price to pay for the sparkling water I always have with the SWG! I would think that the non reactive surface of fiberglass would be similar to vinyl but my pH does rise. Granted I have to add very little acid when I do. 1 gallon lasts close to 6 months!

boscogabby
06-17-2006, 11:00 AM
I came across this anomaly in another thread in this forum I think and have not yet been able to find a reason for the steady pH in vinyl pools.

If you could post a complete analysis, and mention the chemicals you add on a regular basis, it might help to get a better insight. Also what you do when there is an upset through bather load, weather conditions, etc.

Pat
The only chemicals that I add are ph+ (sodium carbonate) and ph-(dry acid) from pool store. This is my first season with SWCG, used to use Baquaglop. I have not yet had an upset through a heavy bather load and I really do not do anything but vacuum after bad weather conditions, I just let the extra water evaporate. My latest test results are 5ppm FC - PH 7.4 - TA 120 - CYA between 60-70 and Calcium hardness at 250.

PatL34
06-17-2006, 02:20 PM
Very helpful thread. I have an Aquarite SWCG and I have a PH of 7.4 and TA of 120 which I am able to maintain pretty consistently without adding acid. However I am reading alot in this thread about adding acid to maintain PH. Is this because most of these pools are plaster and not vinyl? I have an inground 12,000 gallon vinyl pool. Filter runs 12hrs a day and SWCG at 20%.

The only chemicals that I add are ph+ (sodium carbonate) and ph-(dry acid) from pool store. This is my first season with SWCG, used to use Baquaglop. I have not yet had an upset through a heavy bather load and I really do not do anything but vacuum after bad weather conditions, I just let the extra water evaporate. My latest test results are 5ppm FC - PH 7.4 - TA 120 - CYA between 60-70 and Calcium hardness at 250.

I see from your two posts above that you use ph+ and pH-. This tells me that you are using up salt for the process, and will eventually have to add some when the low salt alarm comes on. Dry acid is acid but in a different form, as it dissolves to form sodium sulphate and sulphuric acid. No problem in that but it tends to skew your argument regarding not having to add acid.:(

The total dissolved solids will increase in the pool accordingly, and may well be assisting the TA in acting as an extra buffer to minimize pH bounce. This is just a theory on my part. Someone with better chemistry than I, hopefully may enlighten us further.

Pat

nater
06-17-2006, 03:09 PM
Here's a link to our earlier thread about vinyl pools and pH drift with SWC's:

http://www.poolforum.com/pf2/showthread.php?t=1188

My pool is running closer to the typical SWC operation now that it is in full use. My ph does drift up now over 2-3 weeks (give or take) from 7.2 to 7.6.

When I do knock it back down, I'm having to use a full gallon of acid instead of the 30 oz. the bleach calc predicts, so my water appears to be pretty highly buffered.

Regardless, I absolutely love the SWC. I never dreamed pool maintenance could be this easy. :)

boscogabby
06-17-2006, 06:32 PM
I see from your two posts above that you use ph+ and pH-. This tells me that you are using up salt for the process, and will eventually have to add some when the low salt alarm comes on. Dry acid is acid but in a different form, as it dissolves to form sodium sulphate and sulphuric acid. No problem in that but it tends to skew your argument regarding not having to add acid.:(

The total dissolved solids will increase in the pool accordingly, and may well be assisting the TA in acting as an extra buffer to minimize pH bounce. This is just a theory on my part. Someone with better chemistry than I, hopefully may enlighten us further.

Pat
It was not so much an argument as it was curiosity on my part as to whether or not I was doing something wrong. Should I not use PH+ and PH-? What do you mean by up salt?

PatL34
06-17-2006, 10:27 PM
I meant that you were using up the salt in the pool, and would have to add more later on. By using Muriatic Acid only, you maintain the salt level and raise the pH at the same time, "killing two birds with one stone".

Hope that clears it up. Read the "SWCG Operation" at the beginning again and you will see what I mean.

Pat

brent.roberts
06-30-2006, 02:20 PM
A few posts back it was suggested to measure salt levels every week.

I just put in a new Autopilot digital last week and it will display the salt level. Mine shows 2800 which agrees exactly with the test kit. It also says to add 36 lbs of salt, which it calculates from the setup page where you put in your pool volume.

I keeps getting better and easier.

If you really want to blow the bank, you can add on the ORP kit and an automatic muriatic acid pump .... totally auto.

boscogabby
07-02-2006, 01:08 PM
If my PH is steady at 7.4 and my water is balanced and clear should I add some Muriatic acid to maintain salt levels as part of the process? Should I bring the PH down to 7.2 or just leave it alone? I have not had any problems with low salt levels or anything for that matter. The pool is inground vinyl liner about 8000 gal. FC-10 / Ph-7.4 /TA-110 / CYA-60-70/ CH-250. Pump runs 12hrs a day with Aquarite set at 20%.

PatL34
07-02-2006, 01:54 PM
According to your test figures everything looks good. The FC at 10 ppm is your call, but if you can drop Aquarite output slowly to get the FC to about 3 - 5 ppm, you can get some more life from the cell.

If you want to bring the CH down a bit, use softened water for refill.

Otherwise for the rest, "if it ain't broke, don't fix it".

Pat

PatL34
07-16-2006, 05:43 PM
Have added some extra comments regarding bleach cost vs. SWCG cost in the "Pro" section of the original post (#1).

Pat

waterbear
07-16-2006, 09:50 PM
ONe thing that I am wondering about....I know that saline bags used in the medical field are composed of PVC and that acid will leach out of the bag lowering the pH of the saline solution inside of it. Could something similar be happening in a vinyl lined pool?
Food for though.

PatL34
07-16-2006, 10:19 PM
Waterbear,

The only way to find out is to make some kind of a small pouch or bag of the vinyl liner, without using any kind of glue or PVC cement, add some distilled water, and see if the pH goes down. Then add some salt from a 40 lb. bag of solar salt and check the pH again.

Pat

waterbear
07-16-2006, 10:28 PM
Waterbear,

The only way to find out is to make some kind of a small pouch or bag of the vinyl liner, without using any kind of glue or PVC cement, add some distilled water, and see if the pH goes down. Then add some salt from a 40 lb. bag of solar salt and check the pH again.

Pat
So now all we need is someone with some extra liner material and a heat sealing machine willing to do the experiment!

PatL34
07-17-2006, 03:46 PM
I don't know what the effect of the heat sealing machine would have on the chemistry of the vinyl, so I was thinking of a container shape in the form of a bag or pouch with holes near the edge for a drawstring so as to hold the sides up.

Pat

nater
08-05-2006, 10:21 AM
Bump. I think this one should be a sticky-lots of good info.

Katy-Texas
08-07-2006, 11:22 PM
Just to add my 2 cents.

Have a 26000 gal in-ground plaster & gunite salt water pool for just over a year here in west side of Houston. Chemicals added are:

1) 1 gallon of acid every ~10 days to keep pH down in summer, about 1/2 that in winter.

2) Some cheapo Algaecide when I had some algae in skimmer entrances last summer. Then I read this forum and realized I was too cheap on power and upped my pump time to raise my Cl level to 2 since which I've had no more algae problem.

3) Added 3 x 4.5 lb jugs of stabilizer this spring when 1 year old as almost all disappeared over winter.

4) Couple bags of salt every 3 months, mostly as big rain dump overflows pool via overfill line to street thereby diluting the salt.

Teenage daughters want shower 1/2 time after pool, I never do, feels great.

I do still have quite a bit of spalling of flagstone (sandstone) coping, friend said he heard it was because I had salt pool? Whatever the reason I would not do flagstone again.

Lastly, all my friends with conventional Cl pools still have upsets once-twice a summer/year and get sold tonnes of chemicals from local stores.

Question 1, my pool builder said better to run salt generator at 50% for longer than 100% for shorter (and thereby save power) as hard on salt generator, unknown why?

Question 2, from reading this thread, sounds like vinyl salt water pool owners add way less acid than plaster owners, so something is going on with plaster. My plaster seems to be etching, ie becoming more porous, over time. Is that a negative side effect of salt plaster pools?

Thanks to pat for kicking off great thread, toodles.

PatL34
08-08-2006, 05:58 PM
Thanks Katy for your response.

Your PB is correct in running longer at 50%, and once you have gotten used to the SWCG, you may be able to lower that setting.

The etching you mention could be a function of very low pH, if you are adding Muriatic Acid too much. pH should be between 7.2 - 7.6.

I still have not been able to understand why vinyl pools maintain a steadier pH than plaster pools. Plaster pools will always raise pH because of leaching from the walls, and particularly for new pools that are still being cured. How soon did you add salt after filling?

I waited at least a month before adding salt, after a replaster with Diamond Brite. Another possiblity is if sand was included in the plaster mix. This can be a reason for etching. That's why I had to replaster. The current pool plasterer demonstrated what happens when you don't have sand, by pouring 2 gallons of raw muriatic acid on the steps as the pool was filling up. If there had been any sand, it would have etched immediately.

Hope this helps.

Pat

Katy-Texas
08-09-2006, 09:46 PM
Hi Pat

You say that I may want to lower SWCG from 50% I assume to extend it's life, but then I'd need to circ longer thus more power, guess it's a trade off.

Keep pH in 7.2-7.6 so don't think that's why etching.

Similar to you, pool builder added salt about 1 month after plaster & fill.

Thanks for ideas . . . cheers.

SeanB.
08-10-2006, 03:08 AM
Our construction hasn't begun yet but our PB told us during our design session that we would use a chlorine floater for the first 10 days after filling the pool and then start up our swg. It will be a gunite pool with plaster. Is 10 days long enough, or should we wait longer?

Thanks.

PatL34
08-10-2006, 09:56 AM
Sean, Welcome to the forum.

I would wait longer. At least a month.

Unless your PB has prescribed what you should use in the floater, I would use a combination of regular unscented bleach and trichlor pucks. The pucks will add stabilizer (CYA) until you get to a 60 - 80 ppm level of CYA, and then use bleach exclusively.

Add muriatic acid ONLY to maintain pH at 7.2 - 7.6, and monitor the TA until it gets to about 80 ppm. Then adjust the return jets upwards to maintain that TA level while you are still curing, as it will help to keep the TA down and the curing.

The calcium hardness (CH) will rise naturally as the gunite is curing, so if you have the ability to use water that is no more than 200 ppm CH as initial fill I would do so. If you have to use well water, which I do NOT recommend, then a temporay filter that has the ability to remove metals and CH, HAS to be inserted in the delivery line.

BTW, make sure that there will be no sand in the gunite mix, as this can lead to pitting of the gunite at low pH as it is curing.

Hope this helps with your deliberations with your PB, and good luck.

Pat

PatL34
08-10-2006, 10:16 AM
Hi Pat

You say that I may want to lower SWCG from 50% I assume to extend it's life, but then I'd need to circ longer thus more power, guess it's a trade off.

The function of the SWCG is to generate chlorine, but in so doing, scale tends to build up on the cell membranes. This is removed by reversing the polarity to the membranes, and for this to work properly, the SWCG has to run at least 2 reversals to keep the membranes clear. Check with your manual for the default reversal settings, (usually 4 hours each, total 8) or call your SWCG vendor for more information on this.

Keep pH in 7.2-7.6 so don't think that's why etching.

Similar to you, pool builder added salt about 1 month after plaster & fill.

Thanks for ideas . . . cheers.

Hope this helps.

Pat

Poolsean
08-10-2006, 03:22 PM
Pat, please, no offense intended by commenting on your responses.

Sean - regarding floating a tab feeder. There really is no reason that you can't start the Salt system up right away, with the exception of if the plaster manufacturer can void warranty if you do not wait a certain period of time. This point of view varies widely among the pool plasters.
I would be cautious with floating a tablet feeder, as it will tend to float and stick to one corner of your pool. Erosion of the tablets will also tend to fall out of the feeder and onto the plaster, where it has the potential to cause problems. Perhaps tethering it to a handrail or ladder rail, towards the deep end, rather than by the steps, where it will be even closer to the plaster.

KEEP AN EYE ON YOUR pH LEVEL!! This will cause more problems than anything else. Allow it to drift up, you will end up with calcium stalagmites all over your pool surface.



Per your suggestion to Katy, it's best to check with the manufacturer.

Pool Pilot has the ability to remember where it was in the forward or reverse polarity cycle when the pump shuts off. That way, when it starts back up, it will continue operating in the same direction so as not to cause uneven cell wear. This allows YOU to control how many hours per day you want to run your pump.

As MOST systems don't have this memory, your suggestion of even run times would be correct...but according to the specific Salt Chlorine Generator manufacturer. Everyone's reversal rates are different.
ie, Aquarite reverses every 100 minutes...therefore a run time in 200 minute increments (ie; 200 minutes (3 hrs 20 minutes pump run time - which I can't imagine anyone doing) / 400 minutes (6 hrs 40 minutes - more reasonable) /600 minutes (10 hrs - ahhhh, that's where the 10 hr pump run time comes from!) would ensure even cell wear.

Hope this helps.

steveinaz
08-11-2006, 11:33 AM
Thanks for this thread, great info for pool-newbies like myself. :cool:

Spensar
08-17-2006, 02:57 PM
Very interesting. Are there considerations for winter storage in the North with several months of below freezing temperatures?

On Ebay I see there are several for $500 to $700. Any particular brand recommended? I saw Hayward Aquarite, The Pool Thing, Zodiac and Pentair for sale in that range.

Any caveats or raves or are they all about the same? Does one use the cell up quicker? Warranty and service support issues?

PatL34
08-20-2006, 04:52 PM
I have revised the intial post on this thread, to reflect discussions I had with Chem_Geek regarding the SWCG process.

The main difference is that the pH does not rise. It stays steady. This is the anomaly I saw with members mentioning this with liner pools. However with plaster pools the continuous leaching of calcium hydroxide, will raise the pH and so muriatic acid is needed accordingly. My apologies for any confusion this might have caused.

Pat

waterbear
08-21-2006, 01:18 AM
I have a fiberglass pool and have experienced a pH rise with my SWG. It is slow (and even slower now that I have 50 ppm borates in the water) but it is still happening.

PatL34
08-21-2006, 01:34 PM
Evan,

I suspect that there might be a slight loss of Cl that is not protected by the CYA, even though Richard (Chem_Geek) describes the SWCG operation somewhat as a "closed System". Ex-chemical engineers don't believe in "closed systems".:(

As Richard has mentioned, there are a lot of loose ends regarding the SWCG process that still need to be tied up. Your experience of rising pH is just one.

Pat

bbb
10-24-2006, 11:15 AM
Are there considerations for winter storage in the North with several months of below freezing temperatures?

Good question. I just closed my pool in the Northeast, and it's my first year with the Autopilot. 2 questions:

1) Do any of you bring your cell manifold assembly inside for the winter?

and

2) Since I have the Autopilot control assembly in my shed, I would not be able to bring the cables inside. How would I winterize the cables if I remove the cell manifold assembly (I was thinking in tightly sealed plastic bags)