What is a drain pump?

A small electric pump with an impeller that moves water from the tub to the standpipe or disposal. Most "will not drain" calls are not a dead pump at all but something jamming the impeller or a blocked filter trap in front of it — coins, hair ties, socks and glass shards are the usual finds. A pump that hums without moving water is blocked; a pump that is silent is more likely electrically dead. Note that many retailers sell the bare pump motor separately from the complete assembly with its housing.