gas boiler -- supply and return

[RogerT]

I own a small building with 3 apartments and 3 separate gas boiler hot water radiator heat systems. Each boiler has a circulator pump that is attached to a pipe that goes into the side of the boiler about half way down. Another pipe comes out of the top of the boiler.

I am assuming that where the circulator pump is located is the return water line that goes back into the boiler and the pipe coming out of the top of the boiler is the supply/hot water line that sends hot water up to the radiators to supply them with heat.

Is that correct?

[RBM]

Usually, but to be sure look on the side of the pump. It will have a directional arrow

[Ed Pawlowski]

That is the usual setup. To be sure, when the system has been down for a time, turn up a thermostat and put your hand on the pipe. You'll feel it get hot as soon as the water circulates.

[Stormin Mormon]

Sounds right, to me.

[RogerT]