Why do sodium ions not continuously build up in swimming pools?

[Nathi ORea]

TL;DR

Where do sodium ions go in a pool?

It is killing me trying to understand why sodium ions don't continuously build up in swimming pools.

You add NaCl to a pool. It is electrolysed to H2 and Cl2 leaving Na+ and OH-.

I get OH- builds up over time, and needs to be neutralised by HCl to make NaCl again and water. This would balance out charges, but you quite often put more NaCl in the pool.

I would guess the Cl2 leaves as a gas or perhaps as HCl gas over time, but there must be some mechanism for how Na+ leaves. Can someone help me?

 

[Borek]

No such mechanism, Na⁺ will build up.

 

[Nathi ORea]

No such mechanism, Na⁺ will build up.

Does this mean that our swimming pools become saltier over time? Does this also mean that we have to add more hydrochloric acid as time goes on too because there is more NaOH to neutralise?

 

[Borek]

Does this mean that our swimming pools become saltier over time?

Yes.

Does this also mean that we have to add more hydrochloric acid as time goes on too because there is more NaOH to neutralise?

No. Amount of OH^- produced by electrolysis doesn't depend on amount of Na⁺ present, only on charge that was passed through the solution.

 

[BillTre]

As with any water system, exchanges of water (like splashing water out aand the replacing it with fresh (salt free) water, or overflowing the pool with new water) will reduce the salt levels by actually removing the salt in solution.
A steady state could be achieved if the removal of salt is balanced by the additions of it.

There are several ways to measure the saltiness of water, depending on the range of salinity being measured.

An advantage might of increased salt might be that you will become more buoyant as the salt levels go up.