I have purchased a new pump (Waterway PH2200-6 2hp 2speed) and a new gas heater (Hayward H400FDN) for our 21 X 43 ft oval pool. I have my Brother in law (certified heating and cooling & electrician) hooking up the heater and I see in the installation notes to install a flow meter on the outlet line of the heater. The min/max flow rate for this heater is 30 and 125 GPM. I have 1.5 inch plumbing on the original pump and heater and planned the same for this too. First of all, I have 4 90 degree elbows between the filter and heater intake. Would I be better off to use 2 inch pvc for this section even though the filter output is 1.5 inch? And secondly, this flow meter on the outlet side of the heater, I cannot find a flow meter with even close to the range I need (30 & 125 gpm) in a 1.5 inch size and 2 inch flow meters are much closer but still fall short. Is this flow meter really necessary?