Sir, - In response to T.P. Murphy (April 9th), I have heard it suggested that if we fill a 1.5-litre plastic mineral bottle with water, seal it, and then place it in the lavatory cistern, we will save 1.5 litres of potable water every time we flush the loo. A much simpler measure than laying yet another network of pipes in our streets to carry corrosive sea water. - Yours, etc.,Sean Owens,
St Brigid's Grove,
Killester,
Dublin 5.