New member, with brand new vinyl liner...

[Verndoggy]

Ben:

The Post Office had a little mixup and my test kit only arrived today. In the interim, I added the minimum CYA and bleach for the recommendations of the pool calculator, and have been adding bleach here and there to keep the level up. Things have cleared up (pool looks good visually). Since startup, I've filtered 24/7, and have for the past week run a couple of round of acid & aeration (using my spa jets). I decided to do this, in an attempt to lower the total alkalinity, which showed 270 at the pool store (and has consistently shown over 300 with my old home test kit). I was away for the weekend, so this morning, I found the pH over 7.8 using my old kit, so I added a quart of MA.

After going to the post office this morning, and equipped with new TF-100 test kit in hand (I had ordered before you told me to order the K2006), I tested a few things at lunch and here's what we know today about my 22,500 gallon vinyl pool:

Free Chlorine - 3.5
Total Chlorine - 3.5
Cyanuric acid - 20
Total alkalinity - 380
pH - 7.5

Based on these results, I went ahead and added two more pounds of CYA to a nylon sock and it is presently in my skimmer. I'll add another sock with one more pound of CYA (three pounds total) tonight.

I am planning on adding a quart of MA tonight to bring the pH down in another cycle of acid and aeration per the articles here on the forum, and will probably also add a pint of 10% bleach, based on the pool calculator.

Any thoughts?

Lee

[PoolDoc]

Just maintain chlorine levels, and keep your pH below 7.2.

Do that, and you don't have to worry about aeration or lowering the alkalinity. Just don't raise it (no soda ash or bicarb) and don't add calcium, and let it come down on it's own over time. Check every week or so, so you don't get it too low.

[Verndoggy]

Just maintain chlorine levels, and keep your pH below 7.2.

Do that, and you don't have to worry about aeration or lowering the alkalinity. Just don't raise it (no soda ash or bicarb) and don't add calcium, and let it come down on it's own over time. Check every week or so, so you don't get it too low.

Well, that sounds simple, so I'm on it. However, it raises a couple of questions for me:

1. I thought I'd read on here where the acid/aeration approach was really the only way to reduce the TA. You are saying that just maintaining low pH will reduce the TA over time, right?

2. Is a pH of 7.0 or 6.8 "swimmable"? Does it represent any hazard to our new liner?

3. What problems does the high TA present until reduced?

Thanks, Ben.

Lee

[PoolDoc]

Aeration occurs continuously, if you just use the pool and don't cover it. You can increase aeration rates, through a variety of means. For example, a pool party of middle school boys provides very effective aeration!

But it's not necessary in your case.

6.8 - 7.0 is fine for people and liners. The problem is that, with phenol red testing, 6.8 is about the lowest (most yellow) color. If the pH is 6.8, the solution will be yellow, but if it's 4.0, it will STILL be yellow, with only a small visual difference. What we tell people is that, when they test their pool, 6.8 *really* means 6.8 or LESS, and 8.2 *really* means 8.2 or MORE.

But, in your case, if you use small acid doses to lower the pH, you won't overshoot much, and the high alkalinity (and accompanying off-gassing of carbon dioxide) will naturally cause the pH to rise.

High TA can reduce the efficacy of some algaecides -- but you shouldn't be using any, so that's not really an issue. And, high TA can make it impossible to use cal hypo to sanitize, without clouding the pool . . . so don't use cal hypo.

[Verndoggy]

Got it. Thanks. I'll report back after giving this some time to work.

[Verndoggy]

Ben:

With the water clear and seemingly under control, do I still need to run my filter 24-7 as we reduce the TA by holding down the pH?

It seems like the "aeration" associated with running the system will tend to drive the pH up unnecessarily and, if that is not helpful, I'd like to return to a more standard "daytime" pump & filter operating schedule (like 12 hours per day).

Thanks.

Lee

[PoolDoc]

Driving pH up is what 'uses up' the alkalinity; it's not unnecessary if you want to reduce carbonate alkalinity.

When you are lowering alkalinity, the ONLY way to avoid "driving pH up" is a continuous trickle acid feed. This is what happens on a commercial pool with acid feed controlled by a pH meter.