Low PH Causes

[Simmons99]

New pool 14,000 gallons- exposed aggregate (Diamond Brite). On Sunday - the PH was above 8.2 with a TA of 160 - so I added about 1/2 gallon of Muriatic acid - brushed it in (pump had no power to it yet).

Yesterday - pool people are out and they installed the power to the pump, installed pool light, and started installation of spa light. Last night I tested the water again - PH below 6.8.

My initial thought is that they added a bunch of acid while they were out there, but then I thought - could it be the acid I put in and it just wasn't mixed up yet?

I dropped in 2 lbs of Borax last night, brushed it in, left pump on all night and tested this morning - PH appeared to be a little darker than the 6.8 reading but lighter than 7.2. So I added another 2 lbs.

[KurtV]

Is the builder trying to do a high-acid start-up on your Diamond Brite? That's a very usual thing with that finish and I'd certainly ask him.

[mas985]

According to bleachcalc, 1/2 gallon of acid will lower your PH to about 7.0 but that is an estimate. You are not that far off.

But Kurt is right, with most plaster jobs, you want to keep the PH between 6.8-7.0 for the first week. It saves time in brushing and keeps the plaster smooth.

A true acid start though will require the alk go to 0 and PH drop considerably. Although effective, this is rarely done since it is very risky and can easily damage the plaster if not done correctly.

[Simmons99]

So I should try to keep my PH at 7.0 or less? I thought this would damage the finish to have a really low PH.

[KurtV]

On a new build I really think you should talk to the builder about what he's trying to do with your finish (in case he's doing a high-acid startup) and get him to put the finish care instructions, including water chemistry requirements, in writing. You don't want to give him (and SGM) a cudgel with which to nullify your warranty. In the event of a problem they'll probably both point at each other anyway, but you don't want them to be able to point at you as the source of the problem.

Once you get the care and feeding instructions in writing (if the builder won't give you anything, SGM's Diamond Brite requirements can be found here), maintain a water testing log so that you have some record that you've done your part.

[Simmons99]

Okay - thanks for the info. DH was telling me that you are supposed to keep it below 6.8 so more of the "plaster comes off" so that more of the color shows through. Documentation says closer to 7.4 - so I will try to keep between 7.0-7.4.

I don't think the builder is doing an "acid" start-up they did an acid wash on the finish already and his answer was that you are supposed to add acid everyday - so I don't think he is shooting for a specific number - just doing what someone told him.

We tried talking to the finish guys - but no one spoke English.

[mas985]

So I should try to keep my PH at 7.0 or less? I thought this would damage the finish to have a really low PH.

First, as Kurt suggests, talk with your pool builder as to what they recommend/require. You do not want to void any warranties. Also, they should have given you a start up procedure.

Second, if they do suggest a low PH then that is a good thing. This is the way I started my pool but I had a standard plaster finish. Generally, low PH can be damaging to a pool if it is very low << 6.8 or somewhat low and for a fairly long time (months or years?). The 6.8-7.2 PH is only for a week and meant to dissolve some of the plaster dust on the surface and not the surface itself. You should not lose any of the surface in that time frame.

The real problem comes in if the PH is too high. The plaster dust can harden too quickly and then you will have a rough surface to deal with.

The most important thing to do on start up is to brush and remove the plaster dust as quickly as possible. This will ensure a smooth surfaced pool.


oops - posted at the same time. Stick with the documentation.