I have to drain my pool to lower my CYA level so I just opened the hose drain valve between the pump and my filter and no water comes out. Should I call my pool builder to come and fix the valve or just go buy a water pump? Anyone recommend a good place to buy one (Sears, Home Depot, Leslies?) or model of pump that will work well? How many gph should I be looking for? I'm guessing I need to drain 4,000 gal initially and probably the same later, too.