Beachcomber wrote:What I am unable to understand is that if this is the case why do most people need to use such vast quantities of acid (in one form or another) to keep the pH down.
One would have thought that the hydrochloric acid produced by the breakdown of the chlorine would cause the pH to be permanently low.
Good point Beachcomber. I am struggling to find an answer to that apart from the fact that our water is very alkaline and the constant topping up requires acid to compensate.
I don't think the breakdown of the chlorine is the issue as Hypochlorous Acid is, by definition, acid itself. When it breaks down to HCl the number of Hydrogen ions are the same so that would not change the pH.
I think the age of the pool may be a factor as the grout between the tiles is probably alkaline as well.
On an entirely different subject, our pool now seems to have a resident frog. He seems to spend some time in the garden and some time in the pool - he certainly gives the dawn chorus a new dimension with his croaking. I cannot understand where he could have come from as we are at least 1Km from the nearest open water source.
At least he doesn't seem to be allergic to Agua Fuerte!
Sid
I think I can hear Beachy's pump running from here! 
Good point Beach...my missus said exactly that...hey!...15/30 I think...service Mr Sid