Salt Water Generators Raise Ph Level?

[Gavin]

I heard that these SWG's raise the pH and its really hard to keep the pH down. It requires baby sitting the pool and always adding acid. Is this true?

Thanks.

[Mark]

It is true on my pool but I have a few other things going on like high TA fill water which doesn't help either. Theory is that the hydrogen bubbles from the SWG raise PH by aeration. Lowering TA helps as does borates. However, I chose to build my own acid dispensing system to keep it in check.

[waterbear]

If you do not have new (less than a year old) plaster or have a vinyl or fiberglass pool then pH with a SWG can be held very stable by keeping the TA low (around 70 ppm or even a bit less) and adding borates to 50 ppm to act as a secondary pH buffer. If you have new plaster or water features that create a lot of aeration and cause CO2 to out-gas then you will have a problem with rising ph (SWG or not). If you are using trichlor instead of a SWG (or other unstabilized chlorine source) it will mask this pH rise from the outgassing of carbon dioxide because trichlor is extremely acidic. However, it will cause your cyanuric acid (stabilizer) levels to rise and can lead to an overstabilized pool and the problems associated with this condition. (If you have a cartridge filter or a 'bump' type of DE filter then it most certainly will lead to overstabilization!)

Hope this helps.

[chem geek]

Say waterbear, glad to see you back!

[quantumchromodynamics]

Say waterbear, glad to see you back!

+1

[Gavin]

Thanks guys. I think I will stay away from SWG's. if we get a heavy rain which is very common in the summer the pH shoots up to 8.0 anyway so adding a SWG would mean babysitting the pool everyday.

also heard SWG's cause a lot of erosion with the plaster, rocks and pump/filter system.

[Mark]

4+ years with an SWG with no plaster erosion or anything other problem. I think the problems with SWGs have been overblown and are usually caused by the owner neglecting the pool chemistry and not the SWG itself. It really isn't that hard to keep things in check and no harder than without a SWG. Once you have an idea as to how the unit performs and how the chemistry in the pool changes with changing conditions, then you should be able to get away with testing once a week. But that should be done without a SWG as well. I can now go a couple of weeks without testing and know that the chemistry is still balanced but most of the time I still test every week. Neglecting a pool with or without an SWG is what causes the problems.

[Gavin]

4+ years with an SWG with no plaster erosion or anything other problem. I think the problems with SWGs have been overblown and are usually caused by the owner neglecting the pool chemistry and not the SWG itself. It really isn't that hard to keep things in check and no harder than without a SWG. Once you have an idea as to how the unit performs and how the chemistry in the pool changes with changing conditions, then you should be able to get away with testing once a week. But that should be done without a SWG as well. I can now go a couple of weeks without testing and know that the chemistry is still balanced but most of the time I still test every week. Neglecting a pool with or without an SWG is what causes the problems.

Thanks Mark. so true. yes getting a pool balanced is so important.

and I think what waterbear said about keeping the TA low at 70 might help keep pH more stable. not sure I understand yet about borates and where to buy it from but that sound like a good thing to add.

[Mark]

20 Mule Team borax can be used to add borates. Usually found in the detergent aisle of the supermarket. The poolcalculator can tell you how much borax and acid to add to get to 50 ppm of borates. www.thepoolcalculator.com

[Gavin]

20 Mule Team borax can be used to add borates. Usually found in the detergent isle of the supermarket. The poolcalculator can tell you how much borax and acid to add to get to 50 ppm of borates. www.thepoolcalculator.com

oh ok Thanks I see. yes I have been using 20 mule team borax to raise pH if needed. I've used some of this already so is it still in the pool? and how can I test to see how much is in the pool? I guess I need to know before I add more.

[Mark]

There are borate test strips like these: http://tftestkits.net/Borates-Test-Strips-p29.html

[Gavin]

There are borate test strips like these: http://tftestkits.net/Borates-Test-Strips-p29.html

these are accurate? I heard test strips were not. also what happens if borates get too high?

Thanks.

p.s. placed an order for some Taylor refills. want to get a salt testing kit next...then a TF-100 XL.

only thing is I need my acid demand and the TF kits don't have them.

I like using the acid demand and the table to precisely lower pH.

[chem geek]

You don't have to be that accurate with borates so the test strips are fine for that purpose. Having 30 vs. 50 ppm vs. 70 ppm borates is not that big a deal.

The borates stay in the pool water so only get reduced through dilution (splash-out and refill, backwashing, rain overflow, etc.). You aren't going to get the borates high enough to be a problem. Above several hundred ppm or so you'd start approaching the safety limits for borates, though they have a factor of 100 margin (see this post for more info).

[Mark]

You don't really need to be all that accurate when it comes to borates so they are just to get you into range. In fact, the pool calculator is probably good enough to ball park it.

[Gavin]

Thanks guys.

only one thing I was wondering. I notice the TF kits don't have base or acid demand. I really use the acid demand a lot to add the precise amount of acid to reduce the pH were I want it to be. I've been using a scoop that came with the Cal-Hypo I bought and don't use anymore. It really is very precise and I can be sure using the acid demand table in the K-2006 that the pH will be where I want it in 30mins after adding the acid.

why is the acid and base demands not included in the TF kits?

[quantumchromodynamics]

why is the acid and base demands not included in the TF kits?

I don't think that the acid and base demand tests are that helpful. I never use them.

The Total Alkalinity test will tell you what to do more than the demand tests.

[chem geek]

I have both a Taylor K-2006 and a TF100. I hardly ever use the acid/base demand tests. Sometimes I'll use it to move up/down the pH reading just to make sure I'm reading it correctly, though now I'm pretty used to it. The tables in the Taylor manual for the acid/base demand test and the strength of the drops are unfortunately pretty strong (coarse). They would have been more useful if at half their strength. As Mark said, you can use The Pool Calculator to get a good idea of how much acid/base you need to move the pH. Other factors, such as carbon dioxide outgassing, can change where you end up anyway, to some extent.

If you want an inexpensive source for the Taylor K-2006, you can find it here.

[Gavin]

I have both a Taylor K-2006 and a TF100. I hardly ever use the acid/base demand tests. Sometimes I'll use it to move up/down the pH reading just to make sure I'm reading it correctly, though now I'm pretty used to it. The tables in the Taylor manual for the acid/base demand test and the strength of the drops are unfortunately pretty strong (coarse). They would have been more useful if at half their strength. As Mark said, you can use The Pool Calculator to get a good idea of how much acid/base you need to move the pH. Other factors, such as carbon dioxide outgassing, can change where you end up anyway, to some extent.

If you want an inexpensive source for the Taylor K-2006, you can find it here.

oh yeah ok now I understand. Thanks! I can just use the pool calculator for that instead. But I have a couple pools I'm servicing and don't have an iTouch or iPhone yet so can't use the pool calculator on the road. (I have the K-2006)

so the TA if kept low like 70ppm will keep the pH more stable?

[chem geek]

so the TA if kept low like 70ppm will keep the pH more stable?

Yes, having a lower TA and targetting a higher pH (say, 7.7) will usually result in a lower rate of pH rise.

[Gavin]

so the TA if kept low like 70ppm will keep the pH more stable?

Yes, having a lower TA and targetting a higher pH (say, 7.7) will usually result in a lower rate of pH rise.

I thought it was best to keep pH like 7.4?

so if the Actual Alkalinity (TA - 1/3 CYA) is low that is better to keep pH from moving?

sorry I guess I can answer my own question.....Pool Calculator!

chem you should do some seminars you are so well knowledgeable about pool chemistry.

[Gavin]

If you do not have new (less than a year old) plaster or have a vinyl or fiberglass pool then pH with a SWG can be held very stable by keeping the TA low (around 70 ppm or even a bit less) and adding borates to 50 ppm to act as a secondary pH buffer. If you have new plaster or water features that create a lot of aeration and cause CO2 to out-gas then you will have a problem with rising ph (SWG or not). If you are using trichlor instead of a SWG (or other unstabilized chlorine source) it will mask this pH rise from the outgassing of carbon dioxide because trichlor is extremely acidic. However, it will cause your cyanuric acid (stabilizer) levels to rise and can lead to an overstabilized pool and the problems associated with this condition. (If you have a cartridge filter or a 'bump' type of DE filter then it most certainly will lead to overstabilization!)

Hope this helps.

Waterbear ...if I get TA down to 70 won't that make the actual Alkalinity very low? If CYA is 80? Isn't 1/3 of the CYA part of the TA?

[waterbear]

If you do not have new (less than a year old) plaster or have a vinyl or fiberglass pool then pH with a SWG can be held very stable by keeping the TA low (around 70 ppm or even a bit less) and adding borates to 50 ppm to act as a secondary pH buffer. If you have new plaster or water features that create a lot of aeration and cause CO2 to out-gas then you will have a problem with rising ph (SWG or not). If you are using trichlor instead of a SWG (or other unstabilized chlorine source) it will mask this pH rise from the outgassing of carbon dioxide because trichlor is extremely acidic. However, it will cause your cyanuric acid (stabilizer) levels to rise and can lead to an overstabilized pool and the problems associated with this condition. (If you have a cartridge filter or a 'bump' type of DE filter then it most certainly will lead to overstabilization!)

Hope this helps.

Waterbear ...if I get TA down to 70 won't that make the actual Alkalinity very low? If CYA is 80? Isn't 1/3 of the CYA part of the TA?

That is the idea. You want the carbonate alkalinity very low to mimizie the outgassing of CO2. Cyanurate alkalinity (and borate alkalinity for that matter) have not effect on this. My recommendation of an UNCORRECTED TA of 60-70 ppm is based on the assumption of a CYA of 50-100 ppm, a pH of 7.6- 7.8, and (for plaster and fiberglass pools) a CH of 350 - 450 ppm to keep the water 'balanced (a relative term at best).

The corrected TA measurement is really only useful for the calculation of sautration index (AND you would need to correct for for than just cyanurates. If you have borates in your water you would need to correct for those also!) IMHO, saturaton index is highly overrated and not applied properly in the vast majority of pools and is not somethng to lose sleep over.

Corrected TA is also important when using stabilized chorine sources that are acidic and cause pH to crash when TA is too low. Any error introduced by not correcting for cyanurates is really only significant when you are using acidic trichlor (or dichlor), have very high CYA (the two seem to go hand in hand, don't they?) and you are DEPENDING on your carbonate alkalinity to keep the pH from crashing! THEN it is improtant to know the ACTUAL carbonate alkalinity because if it is too low you are asking for trouble. (IMHO, pH is the most important parameter to look at in dertemining if water is going to be scaling or aggressive to plaster, but that is a topic for another thread and I have spoken quite a bit about this in the past here and on other boards.) When you are using a SWG (or any other unstabilized chlorine source for that matter, where the normal tendency is pH rise from CO2 outgassing) we can put the TA very low and it will actually help stabilize the pool pH.

Hope this clears up a few things. It is important to understand why different recommendations are made for different ways to maintain a pool and to be able to look at the big picture and sort them out.

What works for trichlor in a feeder does not work for a SWG, etc.

[Gavin]

If you do not have new (less than a year old) plaster or have a vinyl or fiberglass pool then pH with a SWG can be held very stable by keeping the TA low (around 70 ppm or even a bit less) and adding borates to 50 ppm to act as a secondary pH buffer. If you have new plaster or water features that create a lot of aeration and cause CO2 to out-gas then you will have a problem with rising ph (SWG or not). If you are using trichlor instead of a SWG (or other unstabilized chlorine source) it will mask this pH rise from the outgassing of carbon dioxide because trichlor is extremely acidic. However, it will cause your cyanuric acid (stabilizer) levels to rise and can lead to an overstabilized pool and the problems associated with this condition. (If you have a cartridge filter or a 'bump' type of DE filter then it most certainly will lead to overstabilization!)

Hope this helps.

Waterbear ...if I get TA down to 70 won't that make the actual Alkalinity very low? If CYA is 80? Isn't 1/3 of the CYA part of the TA?

That is the idea. You want the carbonate alkalinity very low to mimizie the outgassing of CO2. Cyanurate alkalinity (and borate alkalinity for that matter) have not effect on this. My recommendation of an UNCORRECTED TA of 60-70 ppm is based on the assumption of a CYA of 50-100 ppm, a pH of 7.6- 7.8, and (for plaster and fiberglass pools) a CH of 350 - 450 ppm to keep the water 'balanced (a relative term at best).

The corrected TA measurement is really only useful for the calculation of sautration index (AND you would need to correct for for than just cyanurates. If you have borates in your water you would need to correct for those also!) IMHO, saturaton index is highly overrated and not applied properly in the vast majority of pools and is not somethng to lose sleep over.

Corrected TA is also important when using stabilized chorine sources that are acidic and cause pH to crash when TA is too low. Any error introduced by not correcting for cyanurates is really only significant when you are using acidic trichlor (or dichlor), have very high CYA (the two seem to go hand in hand, don't they?) and you are DEPENDING on your carbonate alkalinity to keep the pH from crashing! THEN it is improtant to know the ACTUAL carbonate alkalinity because if it is too low you are asking for trouble. (IMHO, pH is the most important parameter to look at in dertemining if water is going to be scaling or aggressive to plaster, but that is a topic for another thread and I have spoken quite a bit about this in the past here and on other boards.) When you are using a SWG (or any other unstabilized chlorine source for that matter, where the normal tendency is pH rise from CO2 outgassing) we can put the TA very low and it will actually help stabilize the pool pH.

Hope this clears up a few things. It is important to understand why different recommendations are made for different ways to maintain a pool and to be able to look at the big picture and sort them out.

What works for trichlor in a feeder does not work for a SWG, etc.

Thanks. wow lots of food for thought there. I need to run this pool through the pool calculator. getting my salt kit on Monday.

[waterbear]

Thanks. wow lots of food for thought there. I need to run this pool through the pool calculator. getting my salt kit on Monday.

Remember, the pool calulator is just one of many tools to use in maintaining a pool and not the gospel according to Jason. Don't let it rule you. Keep in mind testing error and the error on the volume meanurement of your pool. Also, take into account measurement error when dosing chems. Remembe, we are talking about a pool and not a laboratory experiment! Common sense should be your guide!

Be aware that the Taylor salt kit will usually give a different reading than a cell readout or a meter since the kit is actually testing cloride ion conentration while meters are testing conductivity and use an adjustment table to translate that into salt levels. Also, the titration is a bit tricky to do and often people overshoot this particular one if they are not paying attention and swirling the tube properly. This is one of those titrations where the reaction is not imediate, similar to the calcium hardness titration.

More food for thought!

[Gavin]

Thanks. wow lots of food for thought there. I need to run this pool through the pool calculator. getting my salt kit on Monday.

Remember, the pool calulator is just one of many tools to use in maintaining a pool and not the gospel according to Jason. Don't let it rule you. Keep in mind testing error and the error on the volume meanurement of your pool. Also, take into account measurement error when dosing chems. Remembe, we are talking about a pool and not a laboratory experiment! Common sense should be your guide!

Be aware that the Taylor salt kit will usually give a different reading than a cell readout or a meter since the kit is actually testing cloride ion conentration while meters are testing conductivity and use an adjustment table to translate that into salt levels. Also, the titration is a bit tricky to do and often people overshoot this particular one if they are not paying attention and swirling the tube properly. This is one of those titrations where the reaction is not imediate, similar to the calcium hardness titration.

More food for thought!

Thanks.

what do you think of those Exact electronic tester? any good?

http://www.sensafe.com/PDF/Mailer_Winter_09_USWEB.pdf