High PH SWG

[micon2]

I have a fairly new pool, it was finished in October 2006, it is an 18,000 gallon inground gunite pool with aquavations Hydrazzo finish. It also has a SWG. I have owned 1 pool prior (no SWG) flawlessly maintained with Ben's kit and advice on this forum. I did notice that the PH kept trying to climb...this was even before we added salt or put the SWG online. I was told that it was the process of the plaster curing. So we did add acid about every 3-4 days to keep the PH in range. In December, I noticed the pool appeared to have stains, but on further inspection the surface was rough (only on the horizontal surfaces) and the stain appeared to be sand that was stuck and could not be brushed off. Called the pool builder, who called the plaster company - long story short - They said it was the chemical maintaince, but then I pulled out my pool test log, I had kept flawless records (almost daily) as well as rountinley having the water tested to back up my work by a local shop....the plaster company said it was scale, but did agree to come out and repolish pool. It was done and refilled on 3/10/07, I have tested the water since then and continue to fight a high PH, even with all other tests in line. Here are my current readings:

FC: 3
CC: .5
PH: 7.8
ALK: 120
Cal: 260
CYA: 75
Salt 3.1

I am adding 1/2 gallon of acid every 3 days to keep the PH at 7.4-7.5. The pool is now 5 months old, although only about 6 weeks post re-polish. I am wondering if I have some other kind of problem that I should be looking at. Any help or advice would be much appreciated. (FYI: Maybe pool was filled with Municipal water).

Thank you!

[micon2]

I forgot one thing...I do have an auto cover. We do keep it closed all the time, could that be my problem? Should I open it regularly even though it has been winter here in California or would that even make a difference?

[waste]

Micon, the pH 'creeping' up is often sceen with SWCGs. Evan or Richard could give you the chemistry of why it happens. If I'm remebering correctly, lowering the TA to ~80 - 90 will slow the process and getting ~50 ppm borates in the water will also help (if you do the borate thing, you'll be needing to add a lot of acid to the pool, but once it's done - the pH should stay ~ where you want it). I'd hope that one of them will see this and expound on what I've said

[micon2]

Thanks Waste. I hope to hear from them as well.

[chem geek]

waste is correct. Since you now have an SWG, you should try lowering your TA to 80. Use Ben's Lowering Your Alkalinity procedure to get the TA to this lower level. Try that first and see how much of a pH rise you still have. I suspect it will be less and you will be adding a lot less acid as well. You should also target a higher pH, such as 7.7 instead of 7.5 which will also help (and will be better for chemical balance, unless you increase your CH instead, but you can do that later if this works).

Have you noticed any rise in the CH level over time? If so, then that could be calcium hydroxide from curing, but I didn't think that refinishing involved any new plastering.

The use of 30-50 ppm Borates would help reduce chlorine usage by cutting down the amount needed to kill algae, but with your electric cover you should be having your SWG set pretty low anyway since you shouldn't be losing much from sunlight. I'm a bit surprised that with a cover you still get a lot of outgassing of carbon dioxide since I would have figured it would get pretty saturated rather quickly under the cover. Anyway, try the lower TA first. Then we can see if moving to Borates is something you want to try after that.

Anyway, there's no need to have a high TA with an SWG so let us know what happens when you lower it. Since you keep good logs, we know you'll have a complete set of numbers.

The only other interesting thing is that you are measuring combined chlorine which is very unusual to see in a pool with an SWG. I would leave the cover open for one sunny day (cover it again for night) and see if that takes care of the CC (you may need to turn up your SWG for that day since it will be exposed to lots of sun). You could also shock the pool by adding liquid chlorine, but I'd try the full day of sun first to see if that does the trick.

Richard

[micon2]

Thanks Chem Geek! I will try lowering the TA to 80 and then monitor and post the results. The CA has been rising, so maybe the pool is still curing? I did turn the SWG way down as well, your right that with the cover it does reduce the chlorine usage, and also left the pool open during several days over the weekend. I appreciate your response and assistance.