pH for a dark bottomed plaster pool?

[Bart]

I have a plaster/gunnite pool that is a dark, dark, dark blue color. I also have a SWG.

The paperwork from the pool builder said for "dark bottom plaster pools keep the pH at 7.2", but the guidance from TFP in the Salt Water Generator section says you should keep it at 7.5 - 7.8.

Who is right and why? (I think I know the answer, but why would the pool company tell me to keep the pH so low?)

It's a new pool so the pH is constantly rising, but I'm just trying to figure out where I should try to keep it.

Thanks!

 

[ROB N]

With a new plaster pool The ph will constantly rise. I try to keep mine at the lower end of the scale and have to add ma every few days to combat the rise. We have hard water, and I dont want calcium scale in the pool like on every faucet in the house...

 

[duraleigh]

Follow the instructions of the PB. There is no HUGE difference there so do it his way.

 

[HouTex]

Here's my experience with grey plaster. My pool is about 6.5 months old and the pH is still rising every day. I go through about a gallon of MA each week. My pH will reach the high 7s to low 8s until I add acid to take it back down to around 7.2. My CH is on the high side no mater whose test you believe (TF-100 800; pool plaster contractor 570; Leslie's 400) and over the last couple of months I have developed scaling. The scaling clearly is the result of my CH being too high coupled with the pH above 7.5 (even though it's not at that level for very long). My guess is that because scaling is so obvious on a colored plaster/pebble finish that the plaster companies tell us to keep the pH at the lower range. Wet Edge recommended 7.2-7.4 for my pool.

 

[JasonLion]

The normal Pool School guidance of PH between 7.5 and 8.0 does not apply during the first month with fresh plaster. During the first month about the best you can hope for is to lower PH to 7.2 as often as possible and hope it isn't above 8.0 by the next time you have a moment to look at the pool.

Once several weeks have passed and things settle down you need to balance the water so there won't be calcium scaling and there won't be calcium pitting. There are several ways of doing that, PH high, PH low, PH in-between. The most stable way seems to be with the PH between 7.5 and 7.8 and all of the other levels adjusted to make that work. Trying to keep the PH too low will result in wild swings in the PH, which isn't good.

 

[Bart]

Thanks all!

Jason - the pool was first opened late last fall and then immediately closed. We reopened it very early this spring and the pH has been still shooting up like a rocket. I assume this is normal and your "first month" comment was more of a guideline than an absloute?

Thanks again!

 

[JasonLion]

The "first month" can be postponed by cold temperatures or last longer than a month, so yes a guideline.