Using a lot of acid...

[Kwikee]

I replastered my pool with Sider Crete about 6 weeks ago and expected that as it is a cement based product, there would be a higher than usual acid demand for the first few weeks. This was certainly true and about 27L later it is still requiring more than I would have thought.
I am testing at least every second day, and find I need to add between 500ml and 1L of acid depending on the previous use (deck jets, SWCG) to get the pH back to 7.2-7.4, after it has crept up.
This may well be normal, it just seems a lot. What would be considered "normal" for a 6 week old plaster pool?

 

[duraleigh]

Yeah, I'd say normal. There really is no "exact normal" and I have no experience with sider crete.

The primary point to take away is it really doesn't matter. It is mandatory that your pH stay in the 7's for good water management..... regardless of how much acid it takes to keep it there.

 

[Kwikee]

I thought it could be the case. I just got a 20L drum so it should keep me going for a few weeks at least!

 

[Patrick_B]

Doesn't sound bad to me at all. You'll get good use out of the 20L eventually. I wouldn't worry if it were me.

 

[jblizzle]

New plaster + SWG (aeration) + deck jets (aeration) = ph rise

What is your TA? If that is high, then that is another contributing factor.

 

[HouTex]

I can't tell whether you've always had the SWCG. If so, I suspect you've always dealt with rising pH.

About a week ago I turned my SWCG off because the CL went up to 8.5 and my pH immediately stopped rising.

I suspect that if I didn't have the SWCG I would rarely need to add MA. When my SWCG runs normally I need to add about a quart of MA every 10 days or so to keep my pH in the range.

 

[jerryt]

I can't tell whether you've always had the SWCG. If so, I suspect you've always dealt with rising pH.

About a week ago I turned my SWCG off because the CL went up to 8.5 and my pH immediately stopped rising.

I suspect that if I didn't have the SWCG I would rarely need to add MA. When my SWCG runs normally I need to add about a quart of MA every 10 days or so to keep my pH in the range.

Yes, I find that the SWG is a PH raising machine

 

[JasonLion]

Any kind of fresh plaster/concrete surface is going to raise the PH, TA, and CH levels (especially PH). This will happen rapidly for about a month, and then taper off to more slowly for about a year after application. Colder temperatures can increase the amount of time you spend in the "first month" period.

As others have mentioned, the SWG is also going to cause some PH increase, with the amount of PH increase very much depending on your TA level, higher TA means a more rapid PH increase. By keeping your TA fairly low (60 to 70) you can minimize (or eliminate) the PH increase from the SWG, though high TA fill water can occasionally make that impractical.