How to Vent a Grundfos Pump

Grundfos pumps are used in various applications, one of which is in hot water systems to function as a recirculation device for the water. When operating correctly, the pump keeps hot water moving through the system constantly to ensure that heated water is available whenever you turn on a hot water faucet, in turn, conserving water. When air is in the system, the pump loses efficiency. Venting your Grundfos hot water recirculation pump removes the air, thus restoring the pump's efficiency.

Grundfos has multiple types of domestic hot water recirculation systems. Some systems have a separate dedicated pipe that recirculates the water from the farthest point of hot water use back to the water heater. The pump can run continuously or as needed, depending on the setup. This is very similar to a hot water heating system's piping.

Some recirculation methods, like the Grundfos Comfort System, simplify the idea of this water conservation. These systems do not have a separate dedicated pipe through which to recirculate; instead, they recirculate the hot water back through the cold water pipe using a bypass valve at the furthest sink's supply piping. The pump itself is attached directly to the hot water supply on the water heater, and a bypass valve is at the sink. This type of system is usually used in a retrofit installation to upgrade an existing plumbing system. The Grundfos pump uses a timer and/or a thermal sensor to control itself.

On many systems with dedicated recirculation piping, there is typically a drain and a series of valves near the pump at the water heater. Consider safety first. Shut off the power or turn off the gas supply (as applicable) to the water heater and let it cool. You also want to shut off the power to the pump by either unplugging it or finding the correct circuit breaker and shutting it off.

In some Grundfos models, there is a large vent screw on the pump. Place a large flat-head screwdriver into the slot of the vent screw, and turn the screw counterclockwise to loosen it in place. As you turn the screw, you should hear the sound of escaping air forced by the pressure of water behind the air. Wait for the presence of water around the screw edges to indicate that the air has been removed and then tighten the screw.

Venting a Grundfos pump that has a dedicated recirculation pipe may result in an air-bound system. These steps may not work for your particular situation. Signs of this may be a noisy pump. In this situation, it may be best to call in the professionals.

Bleeding the air in a Grundfos Comfort System is a lot simpler because it is installed directly on the water heater supply piping. With this type of Grundfos pump, you simply need to turn on the hot water at a faucet and let it flow until it has a solid stream. It would be best to do this at the furthest sink, where you will find the bypass valve.