Placement of this filter is up to the church's discretion. It can be plumbed inline on the suction or the return side. If placed on the suction side, it filters the water before it gets to the heater, which would generally be expected to lenghten the life of the heater. Note however, that if the filter becomes blocked because of improper maintenance of other conditions, it could significantly reduce water flow to the heater, possibly causing the heater to overheat and burn out.

Make sure to inspect and clean the filter regularly.