Do SWGs generate high PH levels and require more acid?

[Swampwoman]

Okay, since I am new to pool ownership, new to BBB, and have no dog in any race (yet), I am debating SWG as an ultimate maintenance-helper acquisition (also up for consideration are periostatic pump vs liquidator, etc. -- one of the 3 is destined to replace the auto puck feeder presently part of my setup ). In a "pool training manual" I ound the following comment from an author.

Is the following: a) Hogwash, b) grain of truth with some spin, or c) truth -- in which case what advantages offset this feature? or d) none/all of the above

What the salesmen wont tell the customer is that salt generated chlorination systems produce a VERY high pH chlorine, about a pH of 13 actually and with this ever increasing pH condition much more Muriatic Acid must be added weekly. The system operates and produces chlorine for as long as the pool pump is operating, 8+ hours per day creating a continuously raising pH condition. To balance and keep the water maintained at a pH balance of 7.4 to 7.6 and keep the chlorine effectively in its killing form almost double the regular amount of acid is required adding substantial additional costs for chemical maintenance as well as a constant pH bounce and a much more unstable Total Alkalinity.

Thanks in advance for any thoughts on the subject.

 

[jblizzle]

Not sure about the details they listed. But it is true that a SWG will generally cause pH to rise. However, if you lower your TA you may find a happy balance where the pH does not rise or rises slowly. There are many people here that have SWG and I do not recall reading about any crazy pH and TA fluctuations as your quote seems to imply.

Posted with Tapatalk ... sorry if I sound short ... hate typing on phone

 

[Glock30]

May or may not help.
I went from 0 salt and 0 FC to 3200 ppm salt and 7+ FC in a week and my ph has not moved noticibly.

 

[chiefwej]

Although it was not a huge problem, yes I did find my pH was alway drifting upward requiring frequent additions of MA. Once I found TFP, I found how to reduce my Total Alkilinity which slowed the pH rise. Then added borates which further stabilizes the pH, acts as an algecide, and makes the water sparkle. Now I truly have a Trouble Free Pool!

Basically I test, vacuum, empty skimmers, and swim, swim, swim. Thanks TFP.

 

[ike0069]

I'm not sure about "producing a VERY high pH chlorine", as this make no sense from a chemistry stand point. BUT........, your pH will increase.

The main active biocides in chlorine is HOCl (hypochlorous acid) and OCl (hypochlorite). HOCL is much more effective at killing bio matter, but OCL will also work and neither raise pH in and of themselves. The exact reason for the pH increase in unknown to me, but it does happen.

You only produce chlorine for as long as you run the "cell", not the pump. The amount of time you generate chlorine depends on pool size, chlorine demand, and your particular "cell". I have a 6000 gallon pool and ran my Intex SWG about 4 hrs/day last season during peak summer temps. I bought 2 gallons of 31.5% muratic acid from Lowes for about $11 and I used < 1 quart over the entrie season. This equates to just over 1$ for a season in acid cost.

The increase in acid I had was 100% as I never had to add acid before I switched to salt water. I assume most do not add acid unless they use liquid chlorine. -- Liquid chlorine is blended with sodium hydroxide (caustic) to keep it stable. The caustic in the solution is what increases pH in your pool.

Adding acid will take out alkalinity, but adding sodium bicarbonate will take care of this and you will typically be adding this or soda ash whether you have a saltwater pool or not.

I switched to salt water last season and it was the single BEST thing I've ever done for my pool.

 

[Swampwoman]

Thanks for all the feedback, everyone!
That helps me understands some of the benefits/advantages.

I may slug it out this summer with the bleach to get a bit of a baseline of what to expect...or I may quickly say uncle and forgo other improvements for the SWG. But it sounds like borates = good regardless, so for the moment I'll keep pushing down my TA over the next week or so and then assess.

I welcome pros and cons for systems -- so far have googled compupool, hayward aquarite, and intelli-IC40 -- feel free to share your experiences/life expectancy/cell costs/ known problems/tech bulletins etc. And thanks again!

 

[JasonLion]

ike0069, the PH increases because of CO2 outgassing promoted by the aeration caused by hydrogen bubbles that form inside the SWG cell. This is mostly only an issue when TA is too high. Most pools can have their PH fully stabilized even with a SWG, though sometimes acid additions are still required.

 

[ike0069]

ike0069, the PH increases because of CO2 outgassing promoted by the aeration caused by hydrogen bubbles that form inside the SWG cell. This is mostly only an issue when TA is too high. Most pools can have their PH fully stabilized even with a SWG, though sometimes acid additions are still required.

Interesting, but I do not follow completely.

Do you the exact mechanism causing the pH increase?

 

[JasonLion]

For the technical description, see the Advanced Pool Water Chemistry post and search for "pH Rising".

Speaking more normally, and hopefully not so briefly that it is unintelligible: The TA level in swimming pools is essentially carbonation, dissolved CO2, like the bubbles in soda. Higher TA levels mean more dissolved CO2. As CO2 comes out of solution and escapes from the pool the PH goes up (CO2 dissolved in water is carbonic acid, remove an acid and the PH goes up). The rate at which CO2 can get out is a function of surface area. In a swimming pool the surface is small compared to the volume, so the increase in surface area created by the bubbles is significant, allowing more CO2 to escape and the PH to go up more quickly.

 

[ike0069]

For the technical description, see the Advanced Pool Water Chemistry post and search for "pH Rising".

Speaking more normally, and hopefully not so briefly that it is unintelligible: The TA level in swimming pools is essentially carbonation, dissolved CO2, like the bubbles in soda. Higher TA levels mean more dissolved CO2. As CO2 comes out of solution and escapes from the pool the PH goes up (CO2 dissolved in water is carbonic acid, remove an acid and the PH goes up). The rate at which CO2 can get out is a function of surface area. In a swimming pool the surface is small compared to the volume, so the increase in surface area created by the bubbles is significant, allowing more CO2 to escape and the PH to go up more quickly.

Thanks!

I would not have thought there would be near enough aeration caused by the SWG cell to actually cause a noticeable pH increase, but this makes sense.

 

[HouTex]

My pool is about 18 months old and I'm adding about one gallon of acid a month. That's about $6 a month for acid, but except for topping up my borates and CYA due to rainfall, it's the only thing I have to buy for my pool. Cost isn't really an issue--it's just the inconvenience of having to add acid every 5 days or so.

 

[chiefwej]

My pool is about 18 months old and I'm adding about one gallon of acid a month. That's about $6 a month for acid, but except for topping up my borates and CYA due to rainfall, it's the only thing I have to buy for my pool. Cost isn't really an issue--it's just the inconvenience of having to add acid every 5 days or so.

The acid demand is higher during the first year of operation in a gunite pool. I found mine dropped during the second year, then stabilized once I took control of the TA.

 

[rkgdmd]

I have a 30,000 gallon vinyl liner pool with a Hayward SWCG. I add acid at most once per week. Probably use about 3/4 gallon of acid per month. Not a huge expense. The real cost comes when you pay for and install the SWCG. After that, your chemical costs go down. The pool almost maintains itself. Only you can decide if the up front cost is worth the ease of maintenance trade off.

 

[chiefwej]

I have a 30,000 gallon vinyl liner pool with a Hayward SWCG. I add acid at most once per week. Probably use about 3/4 gallon of acid per month. Not a huge expense. The real cost comes when you pay for and install the SWCG. After that, your chemical costs go down. The pool almost maintains itself. Only you can decide if the up front cost is worth the ease of maintenance trade off.

That's about how much acid I was using, now that I have the TA down, I use is a cup or two a month. I was out of town for two weeks and came back to a pool with all test levels unchanged except a pH that went up from 7.4, but not as high as 7.5!

 

[Brentr]

My pool is about 18 months old and I'm adding about one gallon of acid a month. That's about $6 a month for acid, but except for topping up my borates and CYA due to rainfall, it's the only thing I have to buy for my pool. Cost isn't really an issue--it's just the inconvenience of having to add acid every 5 days or so.

HouTex, we have very small pools. I wonder what our TA should be in order to keep PH from rising. I noted that Jason said that if we lower TA we could reduce the PH rise. I have to add about 22 ozs of MA every week as my PH rises to 7.8. My TA currently is 70. Any thoughts or suggestions would be welcomed