Water testing numbers

[clpoolman]

Hi. this is my first post on TFP but I've been religously reading all the great advice here and also on the Pool Forum. Just a brief background on me. I have had two pools, one a liner inground for four years using Baquacil and a gunite inground using Baquacil for the first six years. Last September I switched to BBB and this season my pool never looked so good and not one problem all year, thank god! :-D I have ruined many shirts and pants using the bleach but it is worth it. I just wanted to post my today's numbers to get some feedback. I have had to constantly had MA to keep my PH at or around 7.5-7.6. It wants to rise sometimes .5 in a week. I could understand this if the pool was still curing but not six years later. I didn't seem to have this when I was using Baq. But all said and done my water is sparkling clear and looks great and has been this way all season. My only additions during the year have been Bleach, MA as needed for PH, Baking Soda to raise TA, and CYA since I only use Trichlor Tabs when on vacation.

FC 6.0
CC 0
PH 7.5
TA 70
CH 350
CYA 40

Water Temp 74

 

[duraleigh]

Cl,

Welcome to the forum. I can only empathize because I have exactly the same issue.....rising pH in a non-salt pool with no apparent cause.

This has been occuring the last four years in my pool. From time to time, I simply let it go to see where it will stop. It seems to stabilize around 8.0 but that makes me too nervous so I drop the MA in to get it back to 7.2.

I guess if that's the only pool water issue we have we are both very lucky......I'll be watching this thread to see if anyone has an answer.

 

[JasonLion]

Welcome to TFP!

I have two suggestions about the rising PH. The simplest thing to try is to let the TA go down a little further, to 50 or 60. That will reduce the CO2 outgassing, which should reduce the rate of PH increase.

You can get a far more dramatic reduction in PH increases by adding borates to 30-50 ppm. This takes a little doing, typically requiring quite a number of boxes of borax and gallons of muriatic acid to compensate for the PH change from the borax. You can use my Pool Calculator to figure out the quantities, see the link in my signature. This will dramatically reduce the rate of PH increase since the borates act as a second buffering system for PH, one that resists increases more effectively than TA does.

 

[duraleigh]

My current T/A floats around 80/90. What happens to the stabilizing effect of T/A on pH if you let it go to 50/60?

As for Borates, it would take approx 30 boxes of 20 Mule Team plus 8 gallons of muriatic to get to 40ppm in my pool. I'm not yet convinced of the benefit/cost ratio..........it seems more cost effective to me to simply add a gallon of acid every 3-4 weeks and not worry about another chemistry level to test and maintain.

 

[JasonLion]

There are various reasons why PH might go up, but the dominant effect is usually CO2 outgassing. Chem Geek produced a wonderful chart of the relative rate of CO2 outgassing at various PH and TA levels. With PH of 7.5 and TA of 80 to 90 the outgassing rate is around 10. If you cut TA down to 50 the outgassing rate will fall to 3.6. So you should see a fairly dramatic improvement by lowering TA.

I agree that adding borates is not for everyone. Borates can make the largest difference for pools with dramatic amounts of aeration, where the PH rise can be very very rapid. Borates also have other advantages: better water feel, algicide, more sparkle, prevents insects, all of which can help make them worth it in particular situations.

 

[clpoolman]

I've read on numerous posts that many pool owners have gone the borates route to provide algae protection and ph stabilization. My major draw back is that my jack russell likes to drink from the pool occassionaly and I'm concerned about the impact. Plus I agree with Duraleigh that the initial costs of the Borax and acid might not be worth the effort. I will try letting my TA go down to 50-60 to see if that helps. I seldom use the waterfall for this very reason and have pointed the returns down towards the bottom of the pool to eliminate any bubbling effects. But now I don't get the surface movement that I had before that really helped the skimmers work. Are the other numbers ok, singlely and in total to provide a balanced pool environment? I thank you all for the help you have given me both in this site and in Pool Forum so I can better manage my pool, therefore I can enjoy it much more. If I hadn't found these sites I'd still be fighting the Bacquacil problem. Thank You!! :-D :-D

 

[duraleigh]

Your other numbers are great. You could even let your FC drift down into the 3-5ppm range for that CYA level and be fine. I'll be very interested in your results when you bring the Alk down

Just to help my understanding, Jason, I'm a little confused on the Alk issue. If we're looking for an Alk range of 80-120 to "help stabilize the pH" as has widely been advocated, then does 50-60 Alk stabilize even more? If so, why don't we recommend that as a target number. I think this was discussed some time ago but I skipped over it in my hurry to get poolside with an adult beverage. :lol:

 

[flintstone]

I add a pint of muriatic acid every two days, as my ph continually drifts up toward 7.8. I have wondered if there are factors such as wind or sun that affect ph, because I live in a very windy area and my pool gets lots of sun. And my dachshunds cannot learn not to drink from the pool. Is there a customary amount of MA that is added to gunite pools less than a year or older than a year old?

 

[JasonLion]

flintstone - That isn't an uncommon amount of acid to be adding, but with some careful balancing of your chemistry I am sure you can get it down from there. One think to keep in mind is that plaster pools that are less than one year old will have some acid demand because of the paster curing which can not be avoided.

duraleigh - Chem Geek wrote a wonderful post on this which I can't find at the moment. Basically, the carbonate alkalinity PH buffer has a "natural" PH of around 8.2 or 8.4. Given enough time with no chemical/dirt/debris additions a pool with a non-zero TA will move towards a PH of 8.2. Because of this natural set point, TA resists PH changes that move away from 8.2 more strongly than it resists PH changes that move towards 8.2, and will pull PH towards 8.2 on it's own over time. High TA works very well when using acidic chlorine sources, such as trichlor. TA is much less effective, and even problematic, when using PH neutral chlorine sources.

Borates provide an additional buffer system that has a much lower natural PH, so they resist PH rises much more strongly than PH decreases in the relivant range. You want some PH buffer, and a little TA is the simplest and quickest way to get that. But for PH neutral chlorine sources a more complex PH buffer system, combining TA and borates, is more effective.

 

[clpoolman]

Jason, All that you said makes perfect sense and I'll probably try borates when I open the season in April. Does this explain why I had PH of 7.5-7.6 all the time without ever adjusting it when I used Bacquacil. In six years I can't remember adding anything for PH any more than once or twice and usually only at spring opening. Nothing during the season.

 

[duraleigh]

Jason, (and Richard)

Very excellent explanation of something I had not understood before. Thanks......really makes sense.

Now, ya'll have gotten me reinterested in borates. I'm gonna' go back to read all the info Waterbear and you posted earlier and gain some more insight.

Of course, I'll still need a loan to purchase all the borax and Muriatic I need but I'm confident the three (Jason, Evan, Richard) of you will be willing co-signers since you're the ones who talked me into it!! :lol: :lol: