How to Change the Pump on a Weil-McLain Boiler

Turn off the electricity for the boiler at the main circuit breaker.

Turn off the water supply for the boiler at the main valve, usually located beneath the boiler. Wait about 30 minutes for the water in the system to cool before proceeding.

Loosen the bleed screws on the radiators farthest away from the boiler by turning them counterclockwise with a bleeder screw wrench.

Drain the boiler at the main drain valve. Exactly where this is located will depend on your boiler installation. Open the drain valve and allow all the water inside the system to run out. There are a number of types of draining systems. Some drain directly outside, while on others you will need to catch the water into a bucket or other container. The amount of water inside will depend on the size of your radiator system.

Loosen the screws holding the service panel for the boiler in place. Pull the service panel off the boiler.

Look for the boiler housing located toward the center of the unit. These housings are cylindrically shaped and connected to the radiator system through couplings at the top and bottom.

Remove the electrical panel cover on the side of the pump. Make a note of which colored wires are attached to which terminals. Loosen the terminal screws and pull the black, white and copper wires off the terminals.

Loosen the couplings at the top and bottom of the pump with a wrench. Hold a towel under the couplings as you unscrew them, as water may seep out.

Loosen the retaining nuts holding the pump body inside the Weil-McLain boiler body using a socket wrench. Gently pull the pump out of the boiler.

Align the new pump so that the inlets are at the top and bottom. Slip the pump into place so that the sockets line up with the retaining bolt holes. Secure in place with the bolts.

Reconnect the water inlet and outlet couplings to the pump body.

Wrap the black wire around the terminal marked "Hot," the white wire around the terminal marked "Neutral" and the bare copper wire to the green grounding screw. If the terminals aren't marked, refer to the notes you made of the wire placement on the original pump. Replace the pump electrical panel cover.

Replace the service cover for the boiler.

Close the bleed screws on the radiators. Turn on the water supply and allow the boiler system to fill. Restore electrical power to the pump.

Start the Weil-McLain boiler and let the system run for about 15 minutes. Open the bleed screws at the topmost radiators. When water starts to seep out, close the bleed screws. Make your way through your heating system, bleeding all the radiators as you go. Top up the system by opening the water supply valve to bring the system up to pressure, if needed.