How long should I expect plaster to raise my pH?

[andreww]

I'm trying to troubleshoot my rapidly rising pH. I have a little 6500 gallon lap pool with an integrated spa and an infinity edge. The pool was completed in February with a dark Pebblefina finish.

http://i.imgur.com/iA0wozD.jpg

I only run the infinite edge for an hour a day to limit the amount of aeration. We haven't been using the spa. I've gotten my alk down to 90-100 but every day my pH will jump from 7.4 to over 8 overnight. I'm currently adding 6.0-16.0 oz of muriatic acid a day to force the pH down. My hardness is stable around 300.

Is this normal? I know that the plaster will force the alk and pH up while its curing, and the small size of the pool doesn't help.

Unfortunately I'm super sensitive to out of balance pH (drives my skin crazy!) so I'm hoping that I can find a sustainable solution. If it keeps rising this much without using any features, will I need to kee adding acid every time we use the spa or have swimmers? Should I consider an automated solution?

 

[JVTrain]

The guideline is 6-12 months as long as the plaster continues to cure. See here: Pool School - Start-up New Plaster

Keep maintaining a pH as you are, careful not to let it go above 8.0 for very long. Your TA will decrease each time you add acid, so keep an eye on that number as well. Eventually your TA will be lower (60-80) and the pH should stabilize.

Are you sure it's the pH balance that's driving your skin crazy? What are your other chemistry levels such as FC and CC? How are you testing?

 

[andreww]

Thank you! That makes sense with the plaster start up.

I do think it's pH. My FC is at 1.6. CC at 0. I ran out of CYA reagent so I don't have a good recent level. I use ozone as a supplemental oxidizer (i know, I know, I purchased it before doing research since a friend with the most beautifully balanced pool recommended it -- but fortunately the pool doesn't get direct sunlight and there is a long contact period). I test fastidiously using the Taylor k-2006 kit.

I'll keep adding acid.

 

[JVTrain]

Unless you're CYA is 0, your FC is too low. I would suspect that in LA, you'd want a CYA level of 60 or 70 ppm depending on how you're chlorinating, with a minimum FC of 3-5 ppm, again depending on type of chlorination. (Which reminds me to ask you to fill out your signature with details about your pool and equipment).

At that low of an FC level, you are risking an algae outbreak and perhaps there could be a bacterial or viral pathogen causing the skin irritation.