BBB weekly?

[Pontiac]

Post subject: Re: So you want to add borates to your pool--Why and HowPosted: May 19th, 2009, 9:58 am
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Location: Silver Spring, MD

Borates won't reduce the total amount of acid you need to use but they will dramatically reduce the frequency of acid additions.

The above statement was posted by Jason. I am considering using borates to help buffer the Ph on a SWG pool. In conjunction to the recent new plaster, there is a large waterfall which contributes to the rather unusual PH rise.

I am probably reading Jason's statement incorrectly, but will I still be adding the same amount of acid on a yearly basis, just not as often?

Also, how well does the BBB method work when the chemicals can only be adjusted on a pool once a week? Meaning how difficult will it be in keeping the PH from getting below 7.5 when one can only add acid once a week? Because the PH window between 7.5 and 7.8 is seems quite small.

Thanks






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[chem geek]

In theory, the borates shouldn't change the total amount of acid that needs to be added but just has you add the acid less frequently since the pH rises more slowly.

In practice, many SWG pools have a lower chlorine demand after using borates, possibly from the mild algicidal properties of the borates. To the extent that this lets one turn down the SWG percentage on-time, then this reduces the SWG aeration and chlorine generation and that reduces the rate of pH rise and the total amount of acid needed to compensate for this.

So many, but not all, SWG pools end up using less total acid over time after they have added 50 ppm Borates.

If you give me your current numbers for TA and CYA as well as starting and ending pH over a known period of time (number of days) before you add acid, then I can calculate for you what would happen after adding 50 ppm Borates -- that is, what the pH rise would be over a week.

Richard

 

[Pontiac]

Thanks for the response. Even after turning down the SWG % of chlorine to zero, the Ph rise continues. TA is 90, CYA is 70. The PH rise is going to be the hard part using once a week numbers. So it will be a while in getting the Ph#'s to you.

Thanks

 

[chem geek]

You don't have to use once a week numbers. Just tell me the pH at one point in time and then the pH some time later and how long between the readings.

Since your pH rises even without the SWG on, you definitely would want to have the TA lower at 70 ppm. If you have a plaster or fiberglass pool, then you would increase the Calcium Hardness (CH) to compensate.

Using your numbers, what I can tell you is that an amount of carbon dioxide outgassing that would cause the pH to rise from 7.5 to 8.0 without borates would only rise to 7.7 with 50 ppm Borates and would take about 2-1/2 times longer to get to 8.0. So, generally speaking, the Borates slow the rate of pH rise by around a factor of 2.5.

 

[Pontiac]

That's about right on the Ph. I've noticed a Ph rise from 7.4 to 8.0+ in a week. Can't tell you how much over 8.0 at this point. The TA is probably around 50 to 70 now with the last addition of a gallon+ of acid. It would sure be nice to cut that acid demand. The 3' waterfall drop from the spa to the pool was toned down some to help with the outgassing.

 

[tedinelkgrove]

That's about right on the Ph. I've noticed a Ph rise from 7.4 to 8.0+ in a week. Can't tell you how much over 8.0 at this point. The TA is probably around 50 to 70 now with the last addition of a gallon+ of acid. It would sure be nice to cut that acid demand. The 3' waterfall drop from the spa to the pool was toned down some to help with the outgassing.

I have the same type of problem. I am adding 8oz of acid every other day or 2. pH will drift from 7.5-7.8. I have tried everything from lowering TA down to 50 (which helped but then my calcite saturation index is out of whack) to trying different brands of acid. It would be really nice to figure this out and just add acid once a week like the rest of the world.

#S are:

TA=70
CH=320
CYA=45

 

[chem geek]

I have the same type of problem. I am adding 8oz of acid every other day or 2. pH will drift from 7.5-7.8. I have tried everything from lowering TA down to 50 (which helped but then my calcite saturation index is out of whack) to trying different brands of acid. It would be really nice to figure this out and just add acid once a week like the rest of the world.

You can always compensate for the saturation index by having a higher CH level and also targeting a higher pH level -- not trying to go below 7.7 or 7.6, for example. The rate of pH rise should be slower at higher pH (as well as lower TA, of course). Also, using 50 ppm Borates will at least reduce the frequency of acid addition, if not the total acid amount.