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Rangeball
07-10-2006, 11:15 AM
One I got my high alk in line, it was time to add more water due to evaporation losses. This shot my alk right back up of course, since my fill water alk is 320 ppm :( It's a viscous cycle that seems to have no end, and I'm contemplating just ignoring alk and enjoying the pool.

PH is again at 8. Pool is crystal clear. I don't have a heater or SWG, and pool is IG vinyl. I don't use calcium, and haven't for a long time.

What am I risking if I let the alk stay high and just try to keep PH below 8 by using acid as needed?

CarlD
07-10-2006, 11:19 AM
You may get some scaling.

Please look at Ben's method for lowering Alk. I think keeping pH that high is a bad idea--it drastically lowers chlorine's effectiveness.

Basically, you lower pH to 7.2 or less, which pulls down the alk, then you AERATE to raise the pH. Repeat the process until Alk is where you want it. Then use Borax to raise the pH to the desired level.

Rangeball
07-10-2006, 11:40 AM
You may get some scaling.

I've not noticed any at all, but will keep an eye on it.


Please look at Ben's method for lowering Alk. I think keeping pH that high is a bad idea--it drastically lowers chlorine's effectiveness.

Basically, you lower pH to 7.2 or less, which pulls down the alk, then you AERATE to raise the pH. Repeat the process until Alk is where you want it. Then use Borax to raise the pH to the desired level.

I've looked at that so many times I think I can probably recite it :) I'm familiar with the process, have done it several times, and frankly am tired of doing it. With such a high starting Alk, by the time I get it down it's time to add more water and the whole process starts all over again.

The elevated PH and reduced chlorine effectiveness is my main concern, but in Ben's "run a high PH pool" page, I get the feeling I may actually be ok, provided I stay ahead of my pool. I'd just feel more comfortable doing so if I knew what the risks of high Alk were.

chem geek
07-25-2006, 10:09 AM
There are two problems with high alkalinity and both can probably be addressed. The problem with scaling can be addressed by having a lower calcium hardness and by keeping the pH lower (but that will be hard due to the other problem with high alkalinity). The other problem is that you will be outgassing carbon dioxide until your pH is at a higher point which is pretty much what you've been seeing.

First of all, just out of curiosity, since you haven't seen any scaling (and don't have cloudy water), what is your Calcium Hardness (CH) level? One thing you can do to avoid even the potential of scaling is to lower CH significantly (unless it is already). If you are going to have a pH of 8.0 with the 320 ppm alkalinity, you could have your CH as low as 50 or even lower (staying in the range of 10-50 would be nice, but even 100 or more may not cause you problems).

As for the pH affecting chlorine effectiveness, that is true, but it doesn't have as much as an effect as you might think because the CYA acts somewhat like a chlorine buffer resisting changes to the chlorine level from pH. Specifically, the disinfecting chlorine (HOCl) level gets reduced by about 15% when you go from a pH of 7.5 to 8.0 (assuming a CYA level of 30 ppm) so that's not too bad and can be easily overcome by running slightly higher levels of chlorine. I suggest you just use Ben's Best Guess CYA chart (http://www.poolforum.com/pf2/showthread.php?t=365) and add about 20% to his numbers to adjust for your 8.0 pH (assuming your CYA is at least 30).

If you look at the following chart, CO2.png (http://richardfalk.home.comcast.net/pool/CO2.png), you can see how higher alkalinity leads to more outgassing of carbon dioxide and that causes the pH to rise. Your levels are off the charts, but I calculate that at a pH of 8.0 and alkalinity of 320 the equivalent outgas rate (the left-hand side Y-axis) is about 10 which is usually pretty stable. You would probably have a hard time keeping your pH much below 7.8

Richard

aquarium
07-25-2006, 10:26 AM
One thing you can do to avoid even the potential of scaling is to lower CH significantly (unless it is already).

How is that done?

chem geek
07-25-2006, 10:31 AM
How is that done?
Unfortunately if the CH isn't already low then the only way to lower it would be a drain and refill. If the fill water is high in CH (we don't know that; we only know it's high in alkalinity), then there isn't a good solution. So you are right that I really need to know not only what the current CH is in the pool but also what the CH is in the fill water. My hope is that the CH in both are already low (which would explain why there's no scaling nor cloudiness).

If the fill water is high in CH, then it's an extra bad situation because any filling after evaporation will introduce even more calcium in the pool. Let's see what the numbers are for CH before panicking. I'm also very interested because there appears to be no evidence of scaling nor cloudiness in this situation so this could give an even higher "limit" to the saturation index for a real-world pool.

Richard

aquarium
07-25-2006, 10:39 AM
Okay,

That's what I thought, but was hoping maybe you knew something I didn't about getting CH lower. :p

High alk and CH usually come together in the fill water, which is my situation. About 220ppm alk, 430ppm CH.

I lower the alk each time I top up, but I know the CH is just getting worse and worse due to evaporation. So far not seeing a problem.

BTW, it's easy to use one of these to aerate each time during a top-off. I just screw it in for a day or so, then remove it:
EDIT - And add acid too. END EDIT

http://i18.photobucket.com/albums/b113/tomwood2/pools/fountainpipe.jpg

http://i18.photobucket.com/albums/b113/tomwood2/pools/fountainwater.jpg

chem geek
07-25-2006, 10:39 AM
I don't use calcium, and haven't for a long time.
Jeez, it would help if I read a post more thoroughly! Rangeball, I would still be interested to know what your calcium level is in your pool and, if you don't mind testing it, in your fill water as well (unless you recently refilled your pool). My guess is that the CH is rather low which is good in your case and explains why you aren't seeing scaling nor cloudiness. [EDIT] I just read Tom's (waterbear's) post which surmises you have high CH -- at any rate, now I'm really interested in your pool's CH reading.:D [END-EDIT]

Richard

chem geek
07-25-2006, 10:47 AM
High alk and CH usually come together in the fill water, which is my situation. About 220ppm alk, 430ppm CH.
Tom,

I am interested in what pH range you are operating with. It will be interesting to see what the relative CO2 outgassing rate is and the saturation index. More real-world data -- I love it! :)

Richard

aquarium
07-25-2006, 10:52 AM
I try to keep it at 7.2-7.6 to maximize the effectiveness of the chlorine. Which, BTW, I can keep at 1.5-2ppm (EDIT - 30ppm CYA) and stay clear blue. If you'll notice in the pic above, this pool is cut into a hill and I think the deep end is cooled by the ground, so it stays close to 84 degrees F, which might be helping.

Rangeball
07-25-2006, 11:02 AM
Jeez, it would help if I read a post more thoroughly! Rangeball, I would still be interested to know what your calcium level is in your pool and, if you don't mind testing it, in your fill water as well (unless you recently refilled your pool). My guess is that the CH is rather low which is good in your case and explains why you aren't seeing scaling nor cloudiness.

Unfortunately, a guess is all I have to go with as well. I don't have the capability to test CH (wanted to order Ben's kit but was waiting for the issues to be resolved, having good luck with OTO kit so figured I'll put off a full kit until next season). I live in a small town, and our one pool store screwed me big time last season and I refuse to do any further business with them. Our fill water is supplied by our local municipality, I'll call them to see what their last water test shows.

In the meantime, I thought I had this issue resolved. Previously I had been aerating WHILE trying to lower PH, didn't work and I got nowhere. Now I lower PH then aerate, and alk was staying low at 130-40ish, PH holding steady. I added about 3" of fill water (ph 7.2 alk 320) last week before my youngest daughter had a swimming party, and after the party my PH was back up to 8. Looks like I'll have to attack it again, and it will probably be a normal part of my pool maintenance life as long as we have such high alk fill water... :(


[EDIT] I just read Tom's (waterbear's) post which surmises you have high CH -- at any rate, now I'm really interested in your pool's CH reading.:D [END-EDIT]

Richard

I thought waterbear = Evan?

;)

chem geek
07-25-2006, 11:14 AM
I try to keep it at 7.2-7.6 to maximize the effectiveness of the chlorine. Which, BTW, I can keep at 1.5-2ppm (EDIT - 30ppm CYA) and stay clear blue. If you'll notice in the pic above, this pool is cut into a hill and I think the deep end is cooled by the ground, so it stays close to 84 degrees F, which might be helping.
So here are the "calculated" numbers for your pool, just so we can see if theory matches reality or not.

At pH 7.2, the CO2 outgas rate is 45.7 which is very high; at 1.5 FC your ppm HOCl is 0.023; at 2.0 FC it's 0.032

At pH 7.6, the CO2 outgas rate is 17.2 which is possibly near "stable"; at 1.5 FC your ppm HOCl is 0.019; at 2.0 FC it's 0.027

So this implies you are having a strong tendency of rising pH. The theory would say that if you started at 7.6, then you would see a much smaller pH drift upwards and would use less acid. In fact, somewhere in the range of 7.6 to 7.8 could be a place where you would be about stable with little or no perceptible drift.

As you can see from the ppm HOCl numbers, they don't change that much with pH (due to CYA acting as a buffer for HOCl). You are at the "low" end of Ben's table range so proabably what he considers to normally prevent algae though he has given me worst-case examples with algae that were at about 0.05 ppm HOCl.

Even if you let yourself drift to a pH of 8.0, your FC of 1.5-2.0 would mean a ppm HOCl of 0.017 to 0.024 which is lower, but not by much. You could just increase your FC to be between 2.0 and 2.5 (or 3.0) and you'd be in pretty much the same shape.

I think the fact that CYA acts as a chlorine buffer to offset the effects of pH is a useful piece of information from the theory that would allow you to operate at higher pH with proper disinfection and algae prevention. If you are willing to take a small chance to try it out, I think it would be worth it given your high alkalinity and CH situation.

Now, as for the saturation index, yours is 1.0 and since you have no evidence of scaling nor cloudiness, that shows that the index can get quite high (we still don't know how high) before scaling is an issue. By the way, do you know your level of TDS? A higher TDS lowers the saturation index. Just based on your alkalinity and CH your TDS has to be at least 860.

Richard

Rangeball
07-25-2006, 11:17 AM
Called City Hall and had them fax over the most recent drinking water quality test report. Didn't contain a reading for Calicum.

Called the Water plant directly, they don't test for calcium :(

Does the 5/6 way drop test kit at Walmart test CH? They have some there for $12, I was thinking about getting one to see where my CYA is now that I used 4 8oz tri-chlor sticks while I was gone for a few days.

chem geek
07-25-2006, 11:24 AM
I thought waterbear = Evan?
;)
Yes, waterbear is Evan's login name. [EDIT] I don't know why I mixed up the name with Tom -- my brain fart. [END-EDIT]

I wouldn't get discouraged with your situation. What I'm trying to work through, along with Evan, is the possibility that you can operate at a higher pH and not worry about your high alkalinity as much. If you try to go to a pH much lower than 7.8, then you will be "fighting" the pH rise due to the outgassing of carbon dioxide and you will be using lots of acid. If instead you let yourself operate in the range of 7.8 to 8.0, then you can still be safe by keeping your chlorine levels about 15% higher than Ben's chart.

Since you are not seeing scaling nor cloudiness, there should be no problem with your running with the high alkalinity. The ideal situation would be for you to outgas CO2 to lose alkalinity at about the same rate as your fill water adds it to fill up after evaporation. You can just monitor your alkalinity over an extended period of time since it should move quite slowly (assuming you start with a pool alkalinity the same as your tap water).

So, bottom line, don't try to fight the situation you've got (high alkalinity) and instead accommodate it via a higher pH operating level.

Richard

chem geek
07-25-2006, 11:27 AM
Called the Water plant directly, they don't test for calcium :(

Do they test for total hardness and is that in the report? I have a calculator that can approximate the calcium hardness based on the typical 4 to 1 Calcium to Magneisum ratio (typical well and ground water -- mountain spring water is closer to a ratio of 2.6 to 1).

The formula is Calcium Hardness (ppm CaCO3) = Total Hardness / 1.412 (for a ratio of 4 to 1 and other conversion factors)
[EDIT]Sorry for the wrong factor the first time[END-EDIT]

Richard

Rangeball
07-25-2006, 11:34 AM
Richard, thanks.

Initially I'd read Ben's "operate at high ph" article, and planned to do so. However since my OTO kit only reads up to 8.2, I decided not to until I had a proper test kit. I assumed once I got my alk down, PH would be fairly stable, and I'd only have to adjust when I added fill like you said, which is where I am now.

I'll try to get current readings for CL, PH and Alk tonight and add them here tomorrow. I need to get another gallon of acid I'm sure.

Just got a call back from the water plant. They had looked in their records and found an entry from 1975 when the city put 3 new wells in (we're still using them) and the CA reading was 62ppm. Our town sits on top of a huge aquifer, and I don't see much evidence looking around that calcium scaling is a big problem (lot's of ag fields using irrigation rigs, etc.).

I'll look at walmart and pick up their OTO kit if it tests CH.

Rangeball
07-25-2006, 11:36 AM
Do they test for total hardness and is that in the report? I have a calculator that can approximate the calcium hardness based on the typical 4 to 1 Calcium to Magneisum ratio (typical well and ground water -- mountain spring water is closer to a ratio of 2.6 to 1).

The formula is Calcium Hardness (ppm CaCO3) = Total Hardness / 2.497 (for a ratio of 4 to 1 and other conversion factors)

Richard

Nope :(

As this was a drinking water quality report, I'm sure they only tested for the required contaminants.

jenpen400
07-25-2006, 11:38 AM
When I filled our AGP a year ago CH was 210 and ALK was 320. I was able to drop the ALK down to 110 but it is much harder to push down from a high number. Once I got the Alk to 220 it was easier. I know how you feel add acid, arate Alk goes down now add water to make up for evaporation and back up it goes. I found that just putting the fountain on low and keeping the ph around 7.4 or lower the alk just keeps creeping down without as much evaporation. Now my alkalinty is fine and my CH is 340. Oh well I guess thats another thread.

Hope this helps
jennifer

waterbear
07-25-2006, 11:43 AM
I'll look at walmart and pick up their OTO kit if it tests CH.
It does but it has some issues....many people, including myself have found that it doesn't always work correctly...a workaround that I have found is to keep adding drops of the first reagent until you get the pink-violet color instead of a yellowish color. I have done this and cross checked with both Ben's kit and Taylor's and it is in the ballpark.

chem geek
07-25-2006, 12:06 PM
When I filled our AGP a year ago CH was 210 and ALK was 320. I was able to drop the ALK down to 110 but it is much harder to push down from a high number. Once I got the Alk to 220 it was easier. I know how you feel add acid, arate Alk goes down now add water to make up for evaporation and back up it goes. I found that just putting the fountain on low and keeping the ph around 7.4 or lower the alk just keeps creeping down without as much evaporation. Now my alkalinty is fine and my CH is 340. Oh well I guess thats another thread.

Hope this helps
jennifer
Jennifer,

I just want to understand clearly. Are you now at an alkalinity of 110 or 220? Is the evaporation less because you've got the fountain on a lower setting? So now you have a balance between losing alkalinty through the aeration (and adding acid to restore the pH) and gaining alkalinity from make-up water for evaporation. Is that right? So your alkalinity is stable, but aren't you adding a lot of acid frequently to keep your pH down? I suppose that may be the tradeoff necessary.



Evap. --> Make-Up --> Alk. Up
^ V
| Fountain
Alk. Down V
pH Down <---- Acid <--- pH Up


Is that your cycle?

Richard

Tredge
07-25-2006, 01:52 PM
Hi Rangeball!

My pool is Still at 340 Alk and I havent bothered to lower it.
Water is 'crystal' clear and no scaling problems.

My CA hardness is quite low...almost 0.
PH stabalizes at ~7.8 but I try to knock it down to 7.4 every few days.

My TDS is quite high due to the SWG. At around 3000 TDS currently.

Hope that helps, I've been happy with the pool and the alk hasnt bothered me a bit.

chem geek
07-25-2006, 02:16 PM
My pool is Still at 340 Alk and I havent bothered to lower it.
Water is 'crystal' clear and no scaling problems.
My CA hardness is quite low...almost 0.
PH stabalizes at ~7.8 but I try to knock it down to 7.4 every few days.
My TDS is quite high due to the SWG. At around 3000 TDS currently.
For what it's worth, the pH stabilization at 7.8 is "predicted" by my spreadsheet and the CO2 graph except that on the graph I made it's off the chart (looks like I need to make a new graph for you high alkalinity folks:) ). As for your calcium hardness, you really don't want it to get to 0 if you have a plaster/grout pool. The problem with near 0 calcium isn't scaling, but corrosion (not of metal, but of plaster/grout). Is your pool vinyl? Is your CYA near 80 since you have an SWG? Mostly I'm asking just to get a sense of everyone's pool so I can see where the models start to break down.

Richard

Rangeball
07-25-2006, 02:46 PM
Hey Tredge :) Glad things are working in your favor :)


Mostly I'm asking just to get a sense of everyone's pool so I can see where the models start to break down.


Richard, my pool fyi-

21,200 gal IG vinyl, 3' to 8' depth.
Last time I tested fill water- PH 7.2, ALK 320.
Chlorinated with .75 gal of 6% bleach nightly. Salt approx 1200 ppm, no SWG.

I ran some tests when I was home for lunch.

TC/FC- 3.0
PH- 7.6
ALK- 170
CYA- 20ish

I was gone the past 3 days, and right before I left the PH was 8+. I added some muratic acid, and this is where things stabilized when I returned.

I highly suspect that with anymore splashing about (another kid fest), my PH will again shoot rapidly up. I always panic when it does because my test kit's upper range is 8.2, and I don't want it to get above that level but won't be able to tell if it does, so I knock it back down. What conditions would it take for my pool to go much higher than 8-8.2?

chem geek
07-25-2006, 03:01 PM
TC/FC- 3.0
PH- 7.6
ALK- 170
CYA- 20ish
What conditions would it take for my pool to go much higher than 8-8.2?
Well interestingly the pH of 7.6 with alkalinity of 170 gives the same "somewhat stable" relative outgassing rate as with Tredge -- his was just over 15 and yours is almost 14.

As for what conditions it would take for your pool to keep rising in pH -- it will always rise until it reaches equilibrium, but the rate of rise will keep slowing down. Unfortunately, it is largely a function of the amount of aeration of your pool so yes, having your kids over and splashing will force up the pH faster. This is not something easily predictable -- it's more something you'll have to keep track of and have a "feel" for. I can tell you that with the "calm" conditions you are now seeing, that a pH of 8.0 will outgass CO2 at about one-third the rate as it is doing now at 7.6 pH so the pH will rise about one-third as fast (again, assuming similar aeration conditions). Aeration is also caused by wind. Basically, only a pool cover would give you a stable and relatively predictable system. Even so, it's kind of eerie that I've now seen several cases that all stabilize near this relative "15" number.

On the other hand, there are those in the rising ph levels (http://www.poolforum.com/pf2/showthread.php?t=4267) thread who experience relatively large pH upward movement without abnormal aeration and with outgas numbers below 15 -- but some of them also do not see the slow drop in alkalinity over time so something else other than CO2 outgassing is causing their pH to rise -- we just haven't figured out what it is.

[EDIT]The number "15" means that the amount of dissolved carbon dioxide in the pool is 16 times larger than the equilibrium amount which is where it would eventually end up if it continued to outgas to air -- that's how far out of equilibrium the pool system is (or how "carbonated" it is).[END-EDIT]

Richard

Rangeball
07-25-2006, 03:48 PM
Thanks Richard.

What would I have to get my ALK to to get PH to stabilize no higher than 7.6?

If this were your pool, what would be your plan of attack? Lower ALK to x each time you have to add fill water?

court475
07-25-2006, 04:16 PM
I'm very interested in this thread. We got a new A.G. pool last week and my fill water Alk was very high, 370 I believe, and Ph was 8.2. I've gotten the Ph down a bit, and the Alk a little as well, but not much. We are adding a fountain today and I hope that helps. With being a newbie it all has my head "swimming"!

Courtney

Rangeball
07-25-2006, 04:26 PM
court, read the "lowering alk" sticky over and over. It does indeed work just like it's typed.

One thing I would highly recommend based on my experience is to not use the fountain to aerate UNTIL you get the ph down to where you want it. Monitor the PH and when it rises to the point you need to knock it back down again (assuming you still need to lower your alk some more) turn off the fountain and again lower your PH, then begin aeration.

Good luck :)

chem geek
07-25-2006, 04:55 PM
Thanks Richard.

What would I have to get my ALK to to get PH to stabilize no higher than 7.6?

If this were your pool, what would be your plan of attack? Lower ALK to x each time you have to add fill water?The short answer is I don't really know.:confused:

Jennifer (http://www.poolforum.com/pf2/showpost.php?p=29013&postcount=18) pushed her alkalinity way down to a normal range where there would be little pH rise from outgassing and she had a slow but definite amount of aeration to intentionally make the pH rise so that when she added acid she lowered alkalinity. This was to compensate for the the alkalinity she was adding through make-up water for evaporation.

You are already down to 170 TA and have fill water that is 320 TA so I would say "go for it" -- do what Jennifer did and use Ben's method to push your TA down further. What you and Jen had are close to the level of "15", but I'll list for you below the pairings of pH and TA at this level and at "10" which has 2/3rds of your current outgas rate.


Level 15 Level 10
pH 8.0 460 TA 320 TA
pH 7.9 365 TA 255 TA
pH 7.8 290 TA 205 TA
pH 7.7 230 TA 162 TA
pH 7.6 185 TA 130 TA
pH 7.5 150 TA 105 TA
pH 7.4 120 TA 85 TA
pH 7.3 95 TA 68 TA
pH 7.2 77 TA 55 TA
pH 7.1 63 TA 45 TA
pH 7.0 51 TA 37 TA


Jennifer is close to the 7.4/120 level and you are close to the 7.6/185 level. So you can continue to push down to her level or because of your kids and their extra aeration you can choose to go down even further to a TA of 85 and a pH of 7.4 (or perhaps a TA of 105 and a pH of 7.5) which should have much less acid demand than you are now experiencing. Just remember Jennifer's "trick" of intentionally allowing for some amount of aeration which will cause pH to rise and then you add acid to bring the pH back down and reduce alkalinity. You should try and do this to the extent you need to for the make-up water that you add to fill-up from evaporation.

The other major alternative you have is to not fight the pH so much and live with a high alkalinity and high pH system. You've been there and don't like it, so that's probably not a good choice.

You asked what I would do. I would get a pool cover and avoid this whole mess. However, if that's not practical, economical, or is too much work, then I think Jennifer's approach is a good one to try.

Richard

Rangeball
07-25-2006, 05:13 PM
Thanks.

I'll read that several more times in hopes I can understand it :)

I had similar experience to Jenn. When my alk was way up, it was hard to move.

Now that I have it below 200 it drops much more readily. I should probably lower it again since I have a few inches before I'll have to add more water to get it down to make subsequent drops easier.

Tredge
07-25-2006, 05:20 PM
For what it's worth, the pH stabilization at 7.8 is "predicted" by my spreadsheet and the CO2 graph except that on the graph I made it's off the chart (looks like I need to make a new graph for you high alkalinity folks:) ). As for your calcium hardness, you really don't want it to get to 0 if you have a plaster/grout pool. The problem with near 0 calcium isn't scaling, but corrosion (not of metal, but of plaster/grout). Is your pool vinyl? Is your CYA near 80 since you have an SWG? Mostly I'm asking just to get a sense of everyone's pool so I can see where the models start to break down.

Richard

I have a heavy epoxy coating on the pool so the grout and plaster are protected.

I have my CYA at 40. I'm reluctant to follow instructions and bump it to 80 :)

jenpen400
07-25-2006, 06:01 PM
Jennifer,

I just want to understand clearly. Are you now at an alkalinity of 110 or 220? Is the evaporation less because you've got the fountain on a lower setting? So now you have a balance between losing alkalinty through the aeration (and adding acid to restore the pH) and gaining alkalinity from make-up water for evaporation. Is that right? So your alkalinity is stable, but aren't you adding a lot of acid frequently to keep your pH down? I suppose that may be the tradeoff necessary.



Evap. --> Make-Up --> Alk. Up
^ V
| Fountain
Alk. Down V
pH Down <---- Acid <--- pH Up


Is that your cycle?

Richard

Last test alkalinity was 140 down from 160 due to lots of evaporation and high fill water. Yes this takes a lot of acid. What I have found is that vigorously aerating it seems I evaporate more water with out rising the ph faster. It could be that more water makes it over the side but the top rail seems dry??? When I get the alkalinity where I want it I just ripple the surface with the jet and even though I replace an inch or two a week it alkalinity and ph remain 110 and 7.5-7.8 with out adding much. I have never needed to raise my ph and my fill water has a ph of 7.5 Hope I did the quote thing right it's my first time.

jennifer

chem geek
07-25-2006, 06:56 PM
Jennifer,

You did great. Thanks for the info. You may have hit on a procedure that may work well for people with high alkalinity tap water. We'll see how Rangeball does with it! :)

Richard

chem geek
07-25-2006, 07:03 PM
I have a heavy epoxy coating on the pool so the grout and plaster are protected.

I have my CYA at 40. I'm reluctant to follow instructions and bump it to 80 :)
OK, thanks for the info. As for the CYA level in SWG pool systems, this is a matter of vigorous discussion at CYA for Salt Chlorinator Pools II (http://www.poolforum.com/pf2/showthread.php?t=4495) in The China Shop. It appears that for most people, following the manufacturers recommended 70-80 ppm CYA level makes the salt cell run more efficiently (your manufacturer may have a different optimum level, but most are pretty high) probably due to the CYA taking away and tying up chlorine away from the generation plates of the cell. Otherwise, too much chlorine builds up near the plates and slows down the generation process. This means that at lower CYA levels you have to have your cell running at higher power and/or longer times in order to achieve the same FC level.

There isn't that much debate about this efficiency improvement with higher CYA. The main debate is over whether Ben's CYA table still needs to be applied -- do you have to have higher FC to prevent algae (disinfection levels still seem OK). Many people do OK, but some do not, so the jury is still out and it's a hotly debated topic. I'm just letting you know what's up -- you should obviously do whatever you feel comfortable with. It's too bad that it's not easy to lower CYA once you've raised it; otherwise, you could just experiment with this.

Richard

Tredge
07-26-2006, 09:06 AM
OK, thanks for the info. As for the CYA level in SWG pool systems, this is a matter of vigorous discussion at CYA for Salt Chlorinator Pools II (http://www.poolforum.com/pf2/showthread.php?t=4495) in The China Shop. Richard

I've followed that discussion since the beginning. I see no evidence why Ben's chart wouldnt apply so I'm sticking with that. Efficiency isnt my main goal, a clean and safe pool is :)

To stay on topic, if I follow your recommendations about a high ALK...its ok to run a pool at 7.8PH? Does this apply to a SWG pool since the generator is far more efficient between 7.2 and 7.6?

Rangeball
07-26-2006, 09:22 AM
Jennifer,

You did great. Thanks for the info. You may have hit on a procedure that may work well for people with high alkalinity tap water. We'll see how Rangeball does with it! :)

Richard

Just found out last night that we're having another kid fest Thursday night. Aeration x 100 :)

I plan to lower my PH to around 7 pre party and let them have at it. I'll test the next morning to see where things leveled out.

Tredge
07-26-2006, 09:36 AM
Just found out last night that we're having another kid fest Thursday night. Aeration x 100 :)

I plan to lower my PH to around 7 pre party and let them have at it. I'll test the next morning to see where things leveled out.

Aeration X100 means a much faster rise in PH. I'd consider adding Acid mid-party to maintain the PH at ~7. Put those kids to work! :)

Rangeball
07-26-2006, 10:28 AM
Aeration X100 means a much faster rise in PH. I'd consider adding Acid mid-party to maintain the PH at ~7. Put those kids to work! :)

From Jen's post above-


What I have found is that vigorously aerating it seems I evaporate more water with out rising the ph faster.

I'm confused. Which one is right?

:)

chem geek
07-26-2006, 01:39 PM
To stay on topic, if I follow your recommendations about a high ALK...its ok to run a pool at 7.8PH? Does this apply to a SWG pool since the generator is far more efficient between 7.2 and 7.6?
Well, the SWG guys say, and many users of SWG pools who report in this forum say, that CYA of 60-80 (70-80) is also much more efficient so I'm not sure how to respond. I suppose that operating at high alk and higher pH may not be a good idea with an SWG system because it is less efficient (based on what you just said).

I agree that you are being safe and prudent to follow Ben's table with an SWG system. I was just pointing out that this is an area of active debate and I do not consider final conclusions to be drawn yet.

Richard

chem geek
07-26-2006, 02:02 PM
I'm confused. Which one is right?
From a technical point of view, more aeration means more outgassing of CO2 which means more of a rise in pH. However, there may be a point of diminishing returns and that may be what Jen saw -- that vigourous aeration caused more evaporation but not a noticeable increase in pH. She wasn't saying that aeration did not cause a rise in pH, but rather that extra vigorous aeration didn't seem to make the pH rise much faster but did increase the evaporation rate quite a bit. She found that a good tradeoff was made by doing some aeration that was less vigorous.

The processes that determine the rate of outgassing and evaporation are very complicated. Both depend on the surface area of the air-to-water boundary (including that boundary in droplets) but the specifics of the rates may be quite different. Nevertheless, if certain droplets were to completely evaporate, then you would lose both the water and the carbonate in that water into the air leaving only some salt (like sea spray) to eventually fall back to the ground or get whisked away by wind.

So I don't have an explanation for Jen's observation of an increase in evaporation without an increase in pH. I could imagine that there is a small increase in pH but that the rate of evaporation increases much more so that it appears that it dominates what's going on. The evaporation process may have a non-linear and more rapid runaway effect compared to the CO2 outgassing, but that's just a wild guess on my part.

Richard

Rangeball
07-26-2006, 02:53 PM
Ok.

I plan to add the acid and drop the PH as low as possible tomorrow morning so the pool will be ready for them swimming 10 hours later. However, they are now calling for scattered thunderstorms, but I guess I'll still be ok if it rains and we call the kids off because I've noticed rain is one heck of an aerator also :)

KurtV
07-26-2006, 03:02 PM
Ok.

I plan to add the acid and drop the PH as low as possible tomorrow morning so the pool will be ready for them swimming 10 hours later. However, they are now calling for scattered thunderstorms, but I guess I'll still be ok if it rains and we call the kids off because I've noticed rain is one heck of an aerator also :)

And beyond that, the pH of normal rain is something like 4.5 to 5.5 (and even lower for "acid rain").

Rangeball
07-27-2006, 02:44 PM
There's that too :)

I dropped PH to 7 last night after work. Didn't check alk because I'm running low on test solution and I know I had room to go. We got rain overnight, PH at lunch was 7.2 (again didn't test alk yet) so I dropped it back to 7.0. We are either having many kids or rain tonight :).

Will check PH again tommorrow morning and report back. I'd love to get alk down and hold PH around 7.4-6 without it creeping up. Evaporation losses have really slowed down the past week, so maybe I can get away with not having to add 2-3" every week.

Rangeball
07-28-2006, 02:40 PM
Wasn't sure if we'd have rain or kids last night. We had both :)

Rained steady for about an hour before everyone showed up. Was sprinkling with clear sky behind it when the party started. PH was 7.

My daughter dove in first. Her dive trail produced a profusion of CO2 bubbles that lasted several seconds after she got out. It was amazing.

The kids proceeded to pound and thrash the pool for all it's worth over the next 3 hours. I noticed the CO2 bubbles less and less as the evening wore on.

After the party, I added bleach and let the pool circulate over night.

I just tested the water at lunch. PH is 7.6, alk is between 120-30. I added the 130 drop before I let the 120 drop do everything it could, and I'm pretty sure if I'd given it time 120 would have done it. So I'll say 125 :)

This is the lowest my alk has been all year long. I plan to go ahead and lower it again because I lost about 1" of water to splash out, and I'm going to have to add more water as the heat wave is returning and evaporation loss will most likely kick back into high gear. Might as well get it as low as I can before I have to add more high alk water to make my job easier later.

Rangeball
07-31-2006, 02:51 PM
Got my alk down to 115, then had to add 3" of water. Lowered PH to 7, and had kids over again yesterday (not near as many). Today PH was 7.6 and alk was only 130. Dropped PH to 7 again, more kids coming swimming this afternoon, will retest alk and PH tonight.

I should end up with a full pool and a 110-20 alk, which should hold me for awhile.

Rangeball
08-01-2006, 02:46 PM
I may have screwed up...

Sunday afternoon I broke my DE filter down for the first time all year. Cleaned it good, fired back up and decided to go ahead and shock the pool, as I haven't since opening for the season months ago. My CYA is around 20ish, so I used enough 6% bleach to get me 12 ppm.

The next day at lunch, I tested TC with my OTO kit. Pure brownish orange, obviously well above the limit of this test. I knew it would be, but I wanted to see what the max level looked like. Next I tested PH and Alk as stated in the above post. PH was 7.6, alk was 130. Added acid to prepare for kids.
Lot's of splashing about.

I just tested TC, PH and Alk. TC is back down to 3, ALK is at 110 but PH, after all the splashing, was 6.8 to below 7.

I'm wondering if the shock level of TC gave me a false high on PH, and I actually lowered it too much. I did use the chlorine neutralizer before testing PH, but only 1 drop as instructed. Could this be the case?

Kids are coming back this afternoon. I plan to test PH again later this evening, and if it hasn't come back up to at least 7.2 by tomorrow will plan to add some mule team 20 for the first time ever.

waterbear
08-01-2006, 05:41 PM
I may have screwed up...


I'm wondering if the shock level of TC gave me a false high on PH, and I actually lowered it too much. I did use the chlorine neutralizer before testing PH, but only 1 drop as instructed. Could this be the case?


Yep, never test your pH when the chlorine levels are high. even with chlorine neutalizer you can get a false high reading. If your OTO was brown you were at a VERY high chlorine level!

Rangeball
08-02-2006, 09:27 AM
Not pure brown, brownish orange :)

I haven't had a chance to check PH today. Lot's of splashing went on yesterday. I'll check it at lunch.

Rangeball
08-02-2006, 04:50 PM
Got a chance to test at noon.

My PH came up a bit, now at 7-7.2.

With an alk of 110, I suspect it should still increase on it's own with further aeration, no?

Unless told otherwise, I'm inclined to leave it as is and just monitor it daily for awhile.

Rangeball
08-04-2006, 09:33 AM
We had two days of many kids splashing about and then about a 1/2" of torrential rain in a 20 minute period. PH is 7.1

I think the verdict is in. I need to bump my PH just a bit. This is the first time ever I've had to.

What is used to increase PH without affecting Alk? I was thinking Borax, but now I'm not so sure.

waterbear
08-04-2006, 09:43 AM
Use borax!