Expert: Mike Fulcher - 8/27/2008

Question
Hi Mike, I have a salt chlorinated swimming pool. Over winter several small white 'holes' (20-30cm diameter, 10 -15cm deep) have appeared on the bottom. Fairly recently the old lady next door has started feeding the birds and the only thing I can attribute the holes to might be the fact that birds flying from her place sometimes as they are challenged by other birds drop largish pieces of white bread in to the pool which they then can't retrieve. These eventually sink to the bottom. As it is winter I had not worried about these but on giving the pool its spring clean I found that the white spots were actually holes. They are definitely new. Could the chemical composition of the bread together with the high salt content create a corrosive environment as the bread sits undisturbed on the bottom of the pool? Ergo corroded holes on the pool bottom?

Answer
Sorry to have taken so long with this question.  My first thought would be that there isn't any link between the bread and holes.  Having been a pool servicer in a past life (before i went to school), I would be concerned that the PH of the pool had fallen to below recommended levels.  Over time this will cause pitting and roughening in concrete pools.  How old is the pool inside surface?  If it's old enough it may just be in need of repair/replacement, if it's newer these holes may be defects due to poor workmnship.  Whatever the case, it would be prudent to have this looked at or repaired.  Rough sufaces will collect and breed algae and make your pool yucky.