pH and liquid chlorine

[HTefay]

Hi, I'm trying to understand why controlling pH has become so difficult since switching from a stabilized granular chlorine to liquid chlorine.
By keeping TA religiously at around 80 I barely needed a coffee cup of acid every three or four weeks with granular chlorine, but since switching to liquid chlorine I need a liter a week of acid to keep pH balanced.

At first I thought the cyanuric acid in the granular chlorine must have been keeping the pH low enough but I'm still maintaining the stabilizer at around 30, so that can't be it. Or can it? Then I thought maybe the pool surface was seeping calcium into the water but it's a fiber glass surface now, so that can't be it either - or can it? Is itt normal to need more acid with liquid chlorine?

Many thanks for any help on offer.

 

[Jezza]

Adding stabilised chlorine will lower pH as it is acidic.

Using Poolmath, adding 1kg of dichlor would bring your pH down by approximately 0.5. so your change to liquid chlorine (which is relatively pH neutral) would mean that you are not experiencing that reduction in pH any longer.

If you bring your TA down to around 60 you might find that you can get away with adding very little acid.

 

[buzzard302]

Exactly. The granular chlorine was acidic, so it kept your pH down. Now that you switched to liquid chlorine, you will have to add additional acid to keep the pH in the correct range. Adding acid regularly will drop your TA over time. Keep doing what you are doing in my opinion. Your TA should continue to drop if you are having to add acid regularly.

 

[HTefay]

I see. The dichlor will add stabilizer which in turn will increase acidity and lower pH. Okay, thank you. May I ask, how often should I add the dichlor after the initial 1kg?

 

[JVTrain]

Dichlor itself is acidic, not necessarily because it adds stabilizer.

The 1 kg number was just an example of what that amount would do to your pH level. You don't need to add this amount and likely shouldn't!

Are you adding baking soda to religiously keep your TA at 80 ppm? If so, why? As was mentioned, allow your TA to drop to 60 ppm as you maintain pH over time and see if the pH is more stable. Your TA will go down each time you add acid.

 

[HTefay]

I've bought into the myth that around 80 TA prevents pH bouncing around. I misunderstood the issue regarding dichlor. Okay... It sounds like I should do nothing, let TA drop to around 60 and see what happens to pH. Thanks.

 

[tim5055]

Yup, many myths around pool care.

As has been pointed out, every time you added the DiChlor it was the same as adding acid to the pool. Now you are adding liquid chlorine which is pH neutral and you still have a need to control rising pH. This is why more acid is needed now.

Lowering the TA may help stabilize the pH rise, but do you have sources of areatio that may be causing pH rise? Waterfalls, sheer descents and anything else that stirs up the water causes natural pH rise.