Location of the pump.

Some modification of the plumbing is nearly always part of this installation. However, if it is not feasible to modify the plumbing, then install it as close to the water heater as possible on the hot side. Make sure you install the pump so that it flows/pumps in the correct direction and support the pump so it doesn't cause a strain on the pipes/connections (if it is not being installed on top of the water heater). And remember to install the circulation valve under a sink as far away from the pump as possible to ensure you get the most benefit from the system. I hope this helps.

The recirculating system MUST be installed on the hot water out line from the water heater in order to work properly.