Check out the pumps at your hydroponics store the better ones use steel shafts and are mag drive no oil, no seals to leak. They are also designed for back pressure and on off service for flood and drain. These guys sell to high end growers that won't tolerate the crap most buy. Surprisingly competively priced. the ones i use are MAXI JET MJ1000 20watt, 291GPH, maximum head is 69" steel shaft and designed for on-off operation.