Since the heater will not be too effective, there should be no problem with putting it before the pump and filter. You just have a leak in the system and will have to pressure test it to find out where it is. The most likely source is the filter basket lid and/or pipe connections, or the pipe connections at the pump.: I have installed a homemade solar heater consisting of about 70 feet of black plastic pipe which is then run to the pump. This line is below water level however I place the skimmer basket at the outlet from the pool whereas before it was connected by a 6 inch nipple to the pump. Would the placement of this basket be a problem (is it needed as a prime for the pump?)? I cannot get air out of the lines so as to pump water freely. Any suggestions would be greatly appreciated. Thank you- Frank J. Ballard