Short Term Low pH

[BoilerSim]

I’m about 45 days into maintaining our new pool, and things are going well so far. Really gotten the hang of testing everything and adding acid, etc. when needed. We’re going to be out of town for four days soon, which is going to be the first time I’ve been away and unable to maintain the water.

My question is, is there any harm in dropping the pH to 7.0 before leaving? It usually rises about 0.2 per day, so this should keep it from going above 8.0 before we get back. It’s a new pool, so I’ve been very careful to let the pH not get too high. The drop would put my CSI around -0.78, all else being equal. For reference, today’s stats:

pH: 7.4
FC: 6.0
CC: 0.0
TA: 80
CYA: 80
Salt: 3650
CH: 310
CSI: -0.43

 

[JoyfulNoise]

If you generally targeted a lower TA (60ppm) and a higher pH (7.6-7.8), your acid demand would decrease. As it is, your TA/pH combo virtually guarantees the pH rise you are seeing (0.2 units per day). When my TA is around 50-60ppm, I can go for about 10-14 days with the pH increasing from 7.6-7.9. You can also consider adding borates to your water as they slow the pH rise on the high end.

Honestly, I think your better off just adjusting the pH down to 7.2 before you leave and then go and come back. The pH when you get back won't be much higher than 7.9-8.0 and your pool really isn't going to suffer irreversible harm with a few days of positive CSI. Low pH is very hard on heat exchangers (copper) as pH is the main driver of corrosion. So if you have to choose between sitting at a really low pH for a couple of days or a high pH, the high pH is the better choice.

 

[BoilerSim]

Thanks! I’ll go with 7.2.

Regarding the TA, I recall reading about exactly what you explained. Unfortunately, I’m still in my warranty period, so have to stay within (or close to) what the builder wants, which is 7.2-7.6 ph and 80-100 TA. I know it’s going to create some more work and eat up acid for a while.