[simon67]

I fill my pool once a year at the beginning of the bath season. It is a simple vinyl-liner with circa 22 cub. m / 5.800 gal water from a water spring. This water has 20 German degrees of hardness and pH around 8.5.

The usual goal for pool water is pH at 7.5. That's what I try to reach. Limestone acts as a 'strong' buffer and would call for huge muriatic acid quantities.

I became impressed by ionic exchange device. I could afford one with capacity 8 cubic m between resin regenerations. Here is what I do not get: if we pull out Ca+ cations and exchange them with Na+ then what have we done about pH? I mean the water coming out of exchanger would contain dissolved NaHCO₃ and Na₂CO₃, and these are two bases and probably buffers.

I am no fan of chemical water softeners nor can I reach hi-end cation & anion exchangers. My question is about simple device that I mentioned. Would it help me to lower pH?

Simon

[Borek]

I wouldn't expect a pH change after removal of Ca²⁺. Note that you have not done anything to anions present - they were there before the exchanger as well.

[simon67]

Borek, thank you for your answer.

Just to clarify me: I don't expect pH lowering with ionic exchanger either. I am aware I would need acid anyway. With this device I'd like to - let me say it simple - remove (or reduce) buffering effect. Then I would measure water pH, put values in online calculators and get the amount of HCl to add. In the past seasons adding acid had almost no effect. Therefore, I immediately thought of CaCO₃ nagging me.

Is ionic exchanger's output solution more pH controllable?

[Borek]

No, the buffering part is not changed.

This is not entirely correct in general, but as a first approximation in water (and especially around the pH you are interested in) it is mostly anions that are responsible for the buffering effect. You have modified only cation composition.

[simon67]

Thank you again for answer.

You gave me info that I was looking for. Ergo purchasing the ionic exchanger isn't a good idea.

Simon