I rebuild heat pumps for an assisted living complex and these are of the horizontal slide in type. They are connected to a water source that is suppose to maintain a constant 67 degree water temp.The problem is that each pump will put out various degrees of cooling/heat.The water temp is the same through out the building.I guess my real question would be.. could the water canister that is with each pump be the problem child? It seems to be a nonservisable devise.Could buildup of mineral deposits maybe keep the unit from extracting enough heat? I change the compressor,reversing valve,filter drier,clean the coil, and change all the electric components but rarely do I get a completed unit to perform like the way I believe it should.Any suggestions would be appreciated. Also I want to point out that the company that made these heatpumps went out of buisness so getting new water tanks is probably going to be impossable. Thank you.