Winter pH prior to Acid Wash

[noelc]

Moved from here

Having similar issues to a new pool plaster with blemishes. PB is thinking to empty and acid wash in the spring. I have to pay to refill.

They also mentioned winterizing with a PH of 7.2 over the winter. I have already closed and covered. Currently maintaining the pool and balancing levels TA and PH.


Any experience on what PH level pool should be at to do a acid wash with pool still filled over time instead of emptying and refilling pool?

Will plan on opening sometime in late April.

 

[ajw22]

Any experience on what PH level pool should be at to do a acid wash with pool still filled over time instead of emptying and refilling pool?

I really don't understand your question.

You really don't want to try and get your pool water to be non-acidic and swimmable after the PH is lowered to 6 or below for an acid wash. The more acidic you get the water, the more aggressive it will be in removing a layer of plaster and with it the blemishes, hopefully.

Do you have a bypass valve for your heater? Do not let acidic water run through your heater or it will rapidly destroy the core.

 

[noelc]

Let me clarify since this post was moved.

I have winterized my pool. This was the first season and there are a couple of white spots, streaks, and some blemished after the plaster was complete and the pool filled. As the season went on some more appeared.

The PB was going to do an acid wash in the spring by draining the pool. However we will likely be responsible for refilling. Another option that was presented was lowering the PH in the pool over the winter. A kind of slow acid wash.

I am planning on lowering the PH to 7.2 for a couple months, prior to re-opening, and was wondering if anyone had any experience or advice on doing/not doing this.

The water will not run through any equipment and I will occasionally balance, brush and circulate with a pump.

Thanks,

 

[mknauss]

It is not just a factor of pH. It is an overall factor called CSI. Put your latest water chemistry test results into PoolMath and see what the CSI is. Then adjust the pH to 7.2 (in PoolMath) and see what the CSI is.

You do not want the CSI to be below -0.6 for very long.

 

[noelc]

Thanks. Just completed that and got a -.64.
FC - 4.38, PH 7.4, CA - 304, TA - 85, CA - 33, Salt 2700

Best I can tell is raise TA a little bit to get CSI over -.6.

Any suggestions or just forget this attempt rather than lowering to 7.2 for a little bit?

 

[mknauss]

The numbers look like pool store tests. Up to you if you want to use them. We do not like to provide guidance based on pool store tests.

I would not change anything if you believe the test results.

 

[ajw22]

TA is the hardest to adjust precisely and raising TA will likely cause PH to rise which is not what you want.

 

[noelc]

Thanks. These are fairly accurate since I do my own independent testing using a Taylor Complete (FAS-DPD clorine) test.
The pool store is relatively close so I do trust their numbers. I recently raised TA before lowering the PH. The TA number is the one I need to retest and adjust. PH is accurate as of today.

I'm looking for advice if lowering the PH over a couple months will have any effect on the blemishes of the plaster surface?

 

[ajw22]

I'm looking for advice if lowering the PH over a couple months will have any effect on the blemishes of the plaster surface?

I think the answer is no one knows. You are doing a science experiment.

 

[Dirk]

Can we back up a bit? I don't know what Ansylbrite Plaster is, but if the installation of it left blemishes and streaks, those could be defects in materials and/or workmanship. If this were my pool I would absolutely reject an acid wash as a fix, and I would also not allow the water to be left for months with an aggressive CSI (anything around -0.6 or below).

Fact: the first year of a pool finish's life is the most critical to its performance: how it will feel, look and last. Water chemistry, especially CSI, should be kept near perfect.

Fact: an aggressive CSI will etch the plaster and leave it feeling less than the smooth surface you presumably paid good money for.

Fact: an acid wash will remove plaster.

That's how it works. It doesn't magically attack stains and blemishes and leave the rest of the pool alone. It will remove a layer of plaster and theoretically take some or all of the undesirable elements with it. And I do mean "some or all," it is not a given that everything will be removed. It is likely that if enough acid is used to remove stains and blemishes it will certainly impact the remaining finish, possibly etching it badly and certainly taking years off its life. Worst case: it'll just make things worse. My pool finish was completely destroyed by an acid wash. The areas that weren't left burned and badly pocked were etched and nowhere near as comfortable as the finish was prior to the wash. And only about 50% of what they were trying to remove got removed. Complete failure and required a redo of the entire finish.

Best case scenario with an acid wash is stains removed and etching minimal and years off its life. It is not a fix-all solution without consequences. IMO an acid wash might be appropriate to liven up an old pool in its last few years, to get rid of some of the staining and clean it up a bit. It is certainly not appropriate to use one on a brand new pool.

IMO, and without knowing any more about your situation than what you posted, it sounds to me like your PB is proposing a quick fix. Enough of one to get you satisfied and get him off the job at minimum expense. It may or may not leave your pool looking OK, it will certainly reduce the useful life of your plaster. Is that what you paid for?

Knowing what I now know about contractors and plaster finishes and acid, the only solutions I would accept is either an attempt to gently abrade the blemishes mechanically (hand sanding), or to redo the plaster if that didn't work.

Not what you wanted to hear, I'm sure. Just my two cents.

Regarding who pays for what: When I had my pool refinished, not only did the contractor pay to have it done, but I charged him for the water, the salt, the startup chemicals and startup labor. Everything. Zero out of pocket. I assume you contracted your PB to build you a nice pool with a nice finish. You shouldn't settle for less or pay more than what you agreed to.

- - - Updated - - -

I'm looking for advice if lowering the PH over a couple months will have any effect on the blemishes of the plaster surface?

I'll answer your specific question with a question: do you think by increasing the acidity of your pool's water enough to destroy plaster blemishes that your unblemished plaster (the rest of the pool) will be unaffected?

 

[noelc]

This is exactly the response I was looking for and it validates my concerns and the conversation I'm currently having with the PB. We are concerned that the work was not done properly and are not agreeing to anything as of yet.

If the technique had some merit than I would attempt it. Sounds like the best game plan is do nothing other than maintain good balance and continue our conversation with the PB. I do not want to affect anything long term especially since it is our first year.

Appreciate the information.

 

[Dirk]

I forgot to mention, if you’re still under warranty with the pool builder, you shouldn’t be applying any fixes on your own. This is the pool builder’s problem, and the pool builder needs to supply the solution. Otherwise, you could inadvertently give him ammo to get out of fixing anything. You should only balance the water to the pool builder’s specifications, and you need to get those specifications in writing, and then track and record your water chemistry every few days, so that you can prove you did nothing but follow the pool builder’s written instructions. That’ll protect your warranty should things go south.