Fine Tuning a Salt Water Pool

I installed a SWCG about a month ago, and have gained an incredible amount of knowledge and information on this Forum. I realize that These are FAQ's but here goes. Approx 11,500 gallon AG pool.

First my readings from this afternoon:

FC 5.0
TC 5.0
CYA 50
Salt 3300
TA 120
pH 7.4

I am currently running the system 5.0 hours per day at 100% output. The FC reading above was taken at 4:00 p.m. approximately 15 hours after the pump shut off, and 4 hours before it is scheduled to kick back on. I have read the "Best Guess" thread regarding the CYA to FC ratio and would like to know if these levels apply to salt Water pools as well as Traditional Chlorine pools.

I am having to add Muriatic acid to keep the pH level down and have read a lot of info on his forum regarding this. I seem to be adding less amounts less frequently as my CYA level rises. I did nurse the CYA up slowly, and I have cut my "on" time from 8 hours to 6 hours to 5 hours.

It would seem likely to me that I can reduce my amount of "on" time or reduce the output percentage still further. With respect to the rising pH level, which would be better, the shorter actual "on" time or the lower percentage?

I would appreciate any and all comments or feed back.

I'm sure the SWG experts (I'm not one!! ;) ) will be by to confirm this soon, but with respect to the rising pH, my understanding is that it is not the percentage of chlorine generated that raises the pH, but rather the operation of the unit itself. So to slow the pH rise, I'd say cut back on the run time. (I'll be interested in the expert's respnses too, because I'm currently taking care of a friend's pool with a SWG and have the same issue)

Janet

Quote:

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Originally Posted by BigTallDumbGuy

FC 5.0
TC 5.0
CYA 50
Salt 3300
TA 120
pH 7.4

I am currently running the system 5.0 hours per day at 100% output. The FC reading above was taken at 4:00 p.m. approximately 15 hours after the pump shut off, and 4 hours before it is scheduled to kick back on. I have read the "Best Guess" thread regarding the CYA to FC ratio and would like to know if these levels apply to salt Water pools as well as Traditional Chlorine pools.

I am having to add Muriatic acid to keep the pH level down and have read a lot of info on his forum regarding this. I seem to be adding less amounts less frequently as my CYA level rises. I did nurse the CYA up slowly, and I have cut my "on" time from 8 hours to 6 hours to 5 hours.

It would seem likely to me that I can reduce my amount of "on" time or reduce the output percentage still further. With respect to the rising pH level, which would be better, the shorter actual "on" time or the lower percentage?

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The chemical equilibriums represented in the CYA/FC ratio charts apply to both salt and non-salt pools.
[EDIT 6/4/10] No. See Watermom's comment and my mea culpa, below [END-EDIT 6/4/10]

If you find the FC climbing too high for your liking you can reduce pump time and/or turn down the percentage on the cell.

You'll get accustomed to this tuning and learn over time what works for your pool. Since rising pH can be an indirect result of cell chlorine production (per accepted wisdom) and a direct outcome of carbon dioxide outgassing from splashing and other types of aeration, this too may be a matter of trying different protocols until one works. pH volatility can be reduced somewhat by allowing your Total Alkalinity to come down over time and (if I understand this correctly) by the addition of borates. When modulating pH rise in my own pool, I reduce TA and cut back the time water features are running (including spa spillover).

BTW I'm not the SWG expert Janet referred to -- just an SWG learner. :)

Quote:

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Originally Posted by polyvue

The chemical equilibriums represented in the CYA/FC ratio charts apply to both salt and non-salt pools.

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This is something we are currently investigating so that we can provide accurate information for our members who have a SWC. Clarifications will be posted shortly.

I am very curious to hear any new "Best Guess" data. Please keep me in the loop. I have learned that FC readings of 5.0 are reasonably good for a Salt water pool, so I am reasonably comfortable with these numbers.

This question has been rolling around in the back of my mind for sometime now. Is there any information on the Chlorine curve in a normal day? Here is what I mean and I can already guess that a lot will depend upon the CYA, the amount of sunlight, and other factors.

If I check the FC at daybreak with my old cheap plastic tester (no pool stores are open at daybreak and I can't test in the dark) I would get a reading of 5.0 as an example. Then if I re-test FC again at sundown, I would think I should see a significant loss say down to 3.0 or something. Now these are not actual readings they're just examples.

When I test in the late afternoon when I get home from work, my actual Chlorine readings are 5.0ish, so would this tend to indicate that I am starting out at something like 10.0 in the morning, or is the normal curve much flatter than that?

BTW, my old cheap plastic tester only goes to 3.0 on the FC scale and says 1.0 - 1.5 FC is "Ideal". I know I need a new tester, and trying to get meaningful readings that are actually "off the chart" with my old one is difficult at best. Again my thought is, I am comparing apples to oranges with a Salt vs. Traditional Chlorine systems.

As always all comments are welcome and appreciated. BTDG

I don't think it really matters whether you lower your "on" time or lower the percentage. I'm assuming by "on" time, you are referring to the time the filter pump is actually "on."

The pH rise is attributed to the amount of time the SWCG is actually generating chlorine. The generation is binary, or it is either generating, or it is not generating. The percentage is the percentage of time that the cell is actually generating chlorine. If you have the percentage at 100%, then the cell is generating 100% of the pump time. If you have it at 50%, the cell cycles on and off and is only generating only 50% of the time, and the other 50% of time it is just passing water through the cell. During the non-generation time, it is not contributing to the pH rise.

For example, say you run your pump for 8 hours, and the percentage is set to 50%. You're generating chlorine for approximately 4 hours. You can lower the generation time to 3 hours by either reducing your pump time to 6 hours, or reducing the percentage to 35-40 percent. Either way, you reduced the generation time by an hour, and both ways should impact the pH rise the same amount.

HOWEVER, in practice, I think you want to run the filter pump (regardless of whether or not you have a salt pool) long enough to filter your pool volume at least once per day. Once you have that run time established, then you adjust the percentage on the chlorine generator to keep your chlorine level where it should be. There may be other reasons to adjust the pump time, but in general, I don't think you should change the pump time to adjust the chlorine level. You should change the percentage to adjust the chlorine level.

This is all based on my own pool and reading this and other forums to learn. Hopefully someone will correct me if I have given any false information.

Yes, "ON" time is when the Pump, Filter and SWCG are all running (it is a package deal). I have it set up as you say in a binary system either everything is on or everything is off.

My thought is this, I'd like to run the system as few hours as necessary to reduce the electric bill. I traditionally ran the pump for 4-5 hours a day before I installed the SWCG.

I will see if I can find any stats on the Pump as far as gallons per minute or per hour when I get home to calculate a complete water turnover.

Thank you very much for your reply. BTDG

Quote:

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Originally Posted by Watermom

This sentence does not appear to be correct information. This is something we are currently investigating so that we can provide accurate information for our members who have a SWC. Clarifications will be posted shortly.

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I should cut back on my nightly dose of cyanuric acid... drinking it hasn't helped my neurons one bit. In my pool (SWG chlorination), I try to maintain a rough minimum FC level of 5% CYA. My understanding, despite what I said above, is that non-SWG pools do better to target 7-8% minimum Free Chlorine. With CYA of 50 ppm, that's 2.5 ppm FC for SWG pools, 4.0 ppm FC for non-SWG pools.

Thanks for catching this!

Quote:

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Originally Posted by polyvue

I should cut back on my nightly dose of cyanuric acid... drinking it hasn't helped my neurons one bit. In my pool (SWG chlorination), I try to maintain a rough minimum FC level of 5% CYA. My understanding, despite what I said above, is that non-SWG pools do better to target 7-8% minimum Free Chlorine. With CYA of 50 ppm, that's 2.5 ppm FC for SWG pools, 4.0 ppm FC for non-SWG pools.

Thanks for catching this!

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Polyvue, LOL amen on the nightly dose of CYA it is worse than diet soda. Your post struck a cord with me and I can't thank you enough. On Memorial Day, we had all the kids in the "New" pool. CYA was 50, FC was 5.0+, pH was 7.6, Salt was 3300. Everyone agreed there was slight eye irritation. I have cut my FC down to be more in line with your numbers. I will keep you posted.

Quote:

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Originally Posted by BigTallDumbGuy

Polyvue, LOL amen on the nightly dose of CYA it is worse than diet soda. Your post struck a cord with me and I can't thank you enough. On Memorial Day, we had all the kids in the "New" pool. CYA was 50, FC was 5.0+, pH was 7.6, Salt was 3300. Everyone agreed there was slight eye irritation. I have cut my FC down to be more in line with your numbers. I will keep you posted.

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Interesting.... When you state that FC was 5.0+ this implies that you're utilizing an OTO (yellow) test that only measures to 5 ppm chlorine. I've had occasion to swim in water with greater than 5 ppm Free Chlorine but did not experience any eye irritation. Are the combined chloramines (CCs) testing at .5 ppm or less? The 3300 ppm salt should further alleviate eye irritation because a salt level up to ~7000 ppm is closer to the typical salinity in tears.


Note for the humor-impaired: Do Not Drink cyanuric acid. I was joking.... as was BTDG. Stick to diet soda.

Hi Polyvue, I think my tester is even older and cheaper than that. It only goes to 3.0 and says that 1.0 - 1.5 is "IDEAL". The 5.0 readings come from the BTDG's best guess or the Pool store. I have been looking for a new tester but haven't found anything in the pool stores that go over 5.0, Which makes me wonder how some of these members are measuring readings like 7.0 etc. I am convinced as you stated in your previous post that FC levels between salt water systems and traditional chlorine systems are apples and oranges.

I went for a swim last night with a FC reading of 1.5 - 2.0 and had no eye irritation for the first time in probably 3 seasons. The bottom of the pool did feel slippery, which rather surprised me. I had turned my SWCG settings to 5 hours at 50% and was seeing 2.5 - 3.0 FC, so as an experiment I tried 5 hours at 40% which is what I swam in last night. Sooooo, assuming that the slippery bottom was a result of too low of a reading, I turned the setting back to 50% and will see what happens tonight.

I am not sure how to test for CC's, however the TC and the FC have had the same reading since I re-filled the pool on May 7th.

Hey, Son!

Do yourself a big favor and order a Taylor K-2006 or 2006C. That way you will be able to test higher cl levels and CC. Can pick one up for under $50 at:

http://www.amatoind.com/taylor-k2006-test-p-555.html

Other places have it, too, of course, but this seems to be the best price anybody has found this spring that I have heard of so far.

Mom

Listen to Mom.

You don't want to have to lay down by your dog bowl again, now do you? :eek:

- - -
I've purchased various chlorine/pH tests over the years but Taylor's K-2006 is, IMO, the very, very best. Its FAS-DPD chlorine test is idiot-proof, accurate and can test ridiculously high levels of chlorine. The others tests are great, as well. If you're like me (a bonafide testing fanatic) consider the 2 oz. reagent size of the K-2006C. Otherwise, the K-2006A will work just fine. Pool stores sell what sells the most -- and most of their customers have no idea what's important so just shop on the basis of price alone. That must be why so few (none in my area) stock the K-2006. Get it on-line, cheap, and be worry-free.......

Quote:

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Originally Posted by polyvue

l. If you're like me (a bonafide testing fanatic) consider the 2 oz. reagent size of the K-2006C. .

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If you find yourself short on some of the reagents, you can always buy the ones you use most in bigger amounts....that's why I like spspools-spas website.

Janet

Heads up on the Taylor 2006 kit from Amato; I ordered mine on Monday and they sent me an email today saying they are out and should be getting some in the next day or so... :( I'm not sure on the 2006C, they might have that in stock. I'm bummed because it will take a week to get to me once they get it, so I'm stuck with the OTO until then...

Quote:

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Originally Posted by polyvue

Listen to Mom.

You don't want to have to lay down by your dog bowl again, now do you? :eek:

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NOOOOOO not the "Go lay by your dish" thing! LOL. I'll be a good dog.

I did a little reading in my faded out instruction sheet in the test kit. The test kit instructions refers back and forth between Total Chlorine and Combined Chlorine as being the same thing.

I have one of those Testers that says to fill with water and drop a tablet marked #1 into the tester, shake well and read the scale. Then drop one tablet marked #3 into the same solution and compare the readings.

Well, doing this, I determined that there is no difference.

Total chlorine and Combined chlorine are not the same thing. TC is the sum of the FC plus the CC. FC is the chlorine that is available to sanitize the water. CC is the chlorine that has already been "used up" sanitizing something in the water. TC is the total chlorine. You want CC to be 0, BTW and therefore, you want your FC to be equal to your TC. (That is kind of a simplified version of each.)

Kind of funny that that online pool store ran out of kits. (Not funny if you are someone waiting for yours, however. :() What do you bet that Pool Forum had something to do with that lack of available kits! Somebody should tell them they have us to thank for their good business and how about a donation to PF! :p:p

O.K. Mom, to the best of my knowledge, every test I had done whether it was my own feable attempt at pool wizardry or tests performed the pool store said that my Total Chlorine and my Free chlorine were the same reading. I don't know if the pool store ever did a CC test. I assume that the Test Kit you recommend will have a CC test.

I was a little confused by the instructions in my own kit. If I do the first part of the test using tablet #1, the sample turns a pinkish color and is read on the scale next to the water sample. Here is where I am confused. If I am reading it correctly, it says to put a tablet marked #3 into the pink solution and compare the first reading with the new reading, which will only be readible if the sample got darker. Now, I would have thought that you would start with a fresh sample of water THEN drop tablet #3 into it to compare the reading.

Now you know how I got my name. Sorry Mom

Quote:

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Originally Posted by BigTallDumbGuy

I did a little reading in my faded out instruction sheet in the test kit. The test kit instructions refers back and forth between Total Chlorine and Combined Chlorine as being the same thing.

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You WANT FC and TC to be the same and in a well maintained pool, they typically are because that would mean that your CC would be 0. But, that is not what you wrote in your post above which I quoted. In that one, you wrote that TC and CC as being the same. Big difference. If your TC and CC are the same, it would mean that your FC was 0 and that would be a BAD thing!

Make sense??

BTW -- the test kit will give you the ability to get FC, CC and TC readings with none of the little tablets. It will be a lot easier to use and read.

Mom

Quote:

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Originally Posted by Watermom

You WANT FC and TC to be the same and in a well maintained pool, they typically are because that would mean that your CC would be 0. But, that is not what you wrote in your post above which I quoted. In that one, you wrote that TC and CC as being the same. Big difference. If your TC and CC are the same, it would mean that your FC was 0 and that would be a BAD thing!

Make sense??

BTW -- the test kit will give you the ability to get FC, CC and TC readings with none of the little tablets. It will be a lot easier to use and read.

Mom

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Nothing makes sense to the BTDG when it comes to swimming pools. Sorry for the confusion. However, the instructions in the lid of the test kit do infact refer to Total Chlorine and Combined Chlorine back and forth as the same thing.

What Watermom is trying to say is that FC (free chlorine) + CC (combined chlorine) = TC (total chlorine). Combined chlorine is USED UP chlorine--you want this reading to be 0.

FC (5) + CC (0) = TC (5) --> Here, all the chlorine is Free chlorine sanitizing your pool.

However, if FC is (2) and the CC is (3), your TC would still be 5:

FC (2) + CC (3) = TC (5) --> In this scenario, you would have more combined chlorine in your pool than free chlorine.

Although I've never seen a 'tablet drop' test that you have, I'm pretty sure it won't measure the FC and CC separately; therefore, you are getting a TC reading. A good test kit, as previously mentioned, will provide you with these separate readings and save you a lot of confusion.

Hope this helps!
Chris

OK, here goes. I am not going into the chemistry behind this now but it has been discussed at length here and in other forums but here is how to set up your SWG. Realize that all these points interact so just doing one without the others is pointless. This does work and there are many who can attest that it does! In fact these are the water balance tips for SWGs that are posted on another pool forum that sprang out of this one. However, the groundwork for all this was laid out and documented on here first!;)

1) Determine the pump run time you need for proper filtration and turnover in your pool. This can be run as one continuous cycle or broken into smaller cycles. if you break it down make the breaks at even multiples of your cells reversal time (for example, Goldline units reverse polarity every 100 minutes and Pool Pilot digital units have a user selectable reversal time with a default of 4 hours.)

2) Adjust your cell output to maintain a 3-5 ppm FC with your given pump run tme. (I know this does not agree with the Best Guess chart but this does work with a SWG system and has been documented time and again!)

3) MAKE SURE YOU ARE RUNNING YOUR CYA AT THE MANUFACTURERS RECOMMENDED UPPER LIMIT! (normally 80 ppm or 100 ppm, depending on the manufacturer). I cannot stress enough how important this becomes to proper pH control!
If you cannot maintain the FC at the 3-5 ppm range and all the above conditions are met it means your cell is really undersized for your pool. You will need to increase the pump run time. Some manufacturers are more conservative (Autopilot, Goldline) than others (Zodiac) when they rate the gallonage a cell can accommodate!

4) LOWER YOUR TA TO 80 PPM OR LOWER. Once again, I cannot stress enough how important this becomes to proper pH control! If you have a plaster or fiberglass pool make sure your calcium is in the neighborhood of 350 ppm or higher to maintain 'water balance'. (don't worry, if you follow this you will be 'in the ballpark! ;))

5) Adjust the pH to 7.6. (If it is lower than this do nothing, it will climb on it's own--unless, of course it's REALLY low, say below 7.2, then start adding the borax to bring it up!) Monitor it daily until you know your pool. When it reaches 7.8 add enough acid to lower back to 7.6 but not lower. (This is where an acid demand test becomes very useful. The Taylor K-2006 does include this test!) The lower you place the pH the faster it rises! We are trying to minimize how often you will need to add acid while at the same time trying to prevent pH spikes that can cause all types of problems with a SWG pool! Soon you will know how much acid to add and how frequently you need to add it to maintain your pH. Your pool maintenance just got easier!:D

6) This step is optional but HIGHLY recommended since it will lower your chlorine demand and further stabilize your pH.
Add borates to 50 ppm. Once you do monitor your FC because, in many cases you will need to lower your cell output to keep your FC in the 3-5 ppm range.
You will also find that your pH will comfortably settle around 7.6 to 7.7 for a longer period of time than before and you will need to add acid less frequently and/or add less acid each time!
I went from about a quart every two weeks to about a cup or so every 6 weeks and have gone as long as 3 months without needing to add any acid to my pool!(fiberglass so it's non reactive,but I have seen benefits in with all pool surface types). I have had customers that have had similar experiences.

To read a detailed account of my first experiment with this read this thread
http://www.poolforum.com/pf2/showthread.php?t=4712
To read the conclusion I came to from the initial experiment (which I have seen repeated time and again in customer's pools and also on other forurms)
http://www.poolforum.com/pf2/showthread.php?t=5419
The reason I did thiis was to see if the claims made for Proteam Supreme (expensive borax), Bioguard Optimzier (expensive borax) and Mineral Springs (their expensive salt mix with borax) and Natural Chemistry's Salt Water Magic (another expensive salt mix with borax) were true or not. Guess what, they are true! (and I live in the same town where the original Proteam test pools were located back in the 80s when they were testing this so I have had the chance to talk to a few people in the industry that remember those experiments).

For a quick update and condensation of the link I posted above, the borates can be added with borax and muriatic acid or by adding boric acid. I have only used the borax and muriatic acid and also Proteam's Supreme Plus which is their pH neutral mix of borax and boric acid.
60 oz. by weight of 20 mule team borax will raise 1000 gallons of water 50 ppm and requires 30 ounces of 20 baum (31.45%) Muriatic acid to maintain the pH.
(12 oz. borax raises 1000 gallons 10 ppm and needs 6 oz acid)

Half the needed amount of borax is dumped into the pool and then half the required acid is then added slowly in the return stream (or diluted in a 5 gal bucket of pool water one or two quarts at a time and then poured into the pool).
Brush the pool to mix the chemicals
Add the second half of the borax and the rest of the acid, brush again.
Circulate for 24 hours non stop then return to your normal pump run time.
Check pH and borate level in 48 hours. If pH is low but in range you are done, If it is high, lower it to 7.6
Actually, I have checked my pH and borates about 2 hours of continuous circulation and if the pH is anywhere between 7.2 and 7.8 I have gone swimming.
For testing borates the LaMotte borate test strip have proven themselves to be superior to all the other strips on the market and provide enough precision to get your borates into the recommended window of 30-50 ppm. I have checked them against the Proteam borate titration test kit time and again they are certainly well in the ballpark! The Proteam test kit is expensive, difficult to find, and not the easiest test to do, btw!
The AquaChek borate strips are much more difficult to read than the LaMotte and seem to have a much shorter shelf life.

I hope you find these tips helpful. They do work, but like I said, onl if you do them all and not just pick and choose. Any one of them will help but when done together the results lead to what the SWG manufacturers promise, a pool that practically takes care of itself!

I hope you find this helpful and if anyone is interested in the actual chemistry then I (and I am sure, chem geek) will be glad to explain it to you. However, just about all of the chemistry info is already here in the forum, much of it in the China Shop!:eek:

Wow! Excellent Post. Thanks Evan. I suspected that the FC reading on a salt water pool could be Lower than traditional Chlorine, and you just confirmed it. I noticed that when I cut my FC numbers down that eye irritation complaints went down too. My pH, TA, and CYA were the same, the only difference was when I cut the "On-Time" back to lower the FC.