Why not purchase a Torbeck valve which is quieter and a water saving? Heres a bottom entry one from a really good cheap company on ebay:
http://cgi.ebay.co.uk/Torbeck-Adjustable-Bottom-Inlet-Entry-Ball-Float-Valve_W0QQitemZ200274964837QQihZ010QQcategoryZ3191QQtcZphotoQQcmdZViewItemQQ_trksidZp1742.m153.l1262
They also do side entry ones too
Joe
January 2009