if it doesn't drain within a set time problems arise.you say it eventually drains which to me means that you have a flow restriction from the pump to the outside world.get the drain hose and put it in a bucket and with a full tub of water it should come out in a solid flow of water with plenty of pressure.if not this is your problem.could be blocked at the back of the filter.shake the drain hose hard and then drain again and see if any dirt comes out.blowing down drain hose can sometimes help to unblock.check filter
ck
December 2009