Can't get pH to reduce to normal levels

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Apr 26, 2018
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Melbourne, Australia
Hi,

I'm new here, but have some familiarity with pools from a previous property we lived at. We have recently put a new salt-water pool in - 25,000 litres - Halo chlorinator (not sure if this is an Australian brand), pH and chlorine sensors, auto-dose acid, etc. I can’t seem to get the pH down to a ‘normal’ range (7.2 - 7.6) from around 8.2. I've been monitoring chemical levels every couple of days with both liquid drop and test strips and putting a fair bit of acid in on top of the auto-dose.
Total alkalinity ~ 100 by liquid drop. Test strip looks ok. (I am assuming a TA of ~ 100 is ok?)
pH ~ 8 - 8.2 by sensor, liquid drop and test strip.
Chlorine - sensor and liquid drop says ok, test strip says low.
Is a pH of 8 in some pools normal?
Otherwise what else should I do to try and reduce the pH?

Thanks,
Paul
 
TA of 100 is alright. To verify though, how are you getting that value? Is it from test strips or using a TF PRO Test Kit or Taylor 2006 Test Kit? At TFP, we strongly recommend against test strips as they are not very reliable.

If your TA is truly 100, and your pH is constantly 8.2, I'd ask if you have water features in your pool that create aeration? Is your pool plaster or fiberglass or...? Do you know what your fill-water pH is?

If you need to reduce pH, you can use MA to bring it down. I'd also suggest downloading the Pool Math app, because the app will be able to tell you how much chemical to add to change values in your pool AND it will allow you to record values for your chemicals and track them historically as well as track chemical additions. There's a FREE version and a paid version of the app.

If you can fill out your signature with more information about your pool and setup, it will help people answer questions in the future.
 
Thanks for that. This is the liquid test kit I've been using and that recommended by the pool company:

4 in 1 Aussie Gold Pool & Spa Test Kit - Chlorine/Bromine, PH, acid demand,TA,

This 4in1 Test kit gives you the ability to test for the four most common parameters used to keep your pool or spa water in a good condition. Free Delivery in Australia
www.aquaneo.com.au www.aquaneo.com.au

The pool finish is a crushed glass aggregate. I don't know the fill-water pH. No water features but I do have a heat pump that runs a fair bit so I guess that would cause some aeration with the warm water coming in?

I will download the pool math app - thanks. The thing with adding acid is that I reckon I've added a couple of litres over the past 3 weeks (200-300 mis each time) on top of the auto-dosing. I was just beginning to wonder why it wasn't coming down and staying down. After I add the acid the pH definitely reduces - often I see it getting to 7.8 on the pH sensor, but then by the next day it's back up to 8/8.1/8.2.
 
The crushed glass is held together by something akin to plaster, I would think? Is it a newer finish, or older?
 
Oh no, you definitely need to keep adding acid to keep the pH in the 7s. The acid additions will just slow down over time.
 
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