pH still rising after borates added

[sharper4]

I recently read up on borates and thought this could be helpful for us. We have a pretty decent size waterfall/grotto and two weeping water falls that cause a lot of water agitation. To help combat the pH rise, I figured it could use borates. I followed the instructions and brought it up to ~40 (which was about 30-35 lbs of boratic acid) but I still find myself adding muratic acid every couple days to lower the pH.

While subjective, the water does *feel* good but it isn't providing the benefit I expected it to. Here are my most recent numbers:

FC: 3.5
pH: 8.2
TA: 75
CH: 250
CYA: ~50
Borate: ~40
Temp: 87*

Is it best to increase the TA a little now that the borates are added or should I leave it on the low end (which I read was a good idea when adding borates)?

 

[Richard320]

You're caught in a losing battle with all that aeration. The best the borates can do is slow down the pH rise, it won't stop it. Just keep adding acid to lower pH to 7.2 and drive the TA lower. At some point, hopefully, the pH will stabilize within range and stay there for a few days or a week at a time.

 

[sharper4]

Lower to 7.2?
I mentioned to the PB that I tried to keep it at 7.4-ish because of the liquidator and he balked, saying acidic water would do long term damage to the heater if I kept the pH too low. The pool calc is telling me to keep it in the 7.5-7.8 range. Just want to make sure before making the change again (easy as it is to make).

 

[JoyfulNoise]

Lower to 7.2?
I mentioned to the PB that I tried to keep it at 7.4-ish because of the liquidator and he balked, saying acidic water would do long term damage to the heater if I kept the pH too low. The pool calc is telling me to keep it in the 7.5-7.8 range. Just want to make sure before making the change again (easy as it is to make).

Read the PoolSchool article on lowering TA. You only drop the pH down to 7.0-7.2 so that the TA is decreased and then the aeration brings the pH back up again. You would only be at low pH for maybe a few hours, max maybe a day. The CO2 out gassing rate is very high at low pH and that is brings the pH up again. Your heater will be fine.


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[chem geek]

Having the pH lower short-term during the procedure for lowering the TA will not damage the heater. It takes substantially lower pH for a longer period of time to do that.

After your TA is lower then you'll be targeting a higher pH of 7.7-7.8 and you should see a lower rate of pH rise and less acid that needs to be used. The question is how low to lower your TA. At least get it down to 60 ppm. After you've settled on a TA level and have your pH back up, then to protect your Stonescape surface you can raise your CH level to compensate for the saturation index (at 60 ppm TA you'll probably target around 400 ppm CH).