Help with chemistry please...

Question

Chlorination is used to keep pools and spas fit for human use. keeping in mind that spas contain many metal and plastic pipes and other dangers, please can anyone give reasons why chlorine gas is not bubbled through spa water?

Answer 1

What you consider to be a chlorination is in fact a treatment with  sodium hypochlorite (NaClO). This is because elementary chlorine in water dissolves in hypoclorite: Cl2 + H2O <=> HClO + HCl

This equilibrium is on the left side so much of the chlorine doesn't react and can harm lungs and skins of swimmers and drinkers. With NaClO treatment such problems don't arise.

Spas are special natural waters which are delivered untreated ( no component  removed nor any component added). This is usually because of legal restrictions (at least here in Germany). So adding chlorine is prohibited because of negative health effects and the use of NaClO is prohibited because in such a case a component would be added.

Answer 2

It is poisonous.