Washer Won’t Stop Filling

When a washing machine will not stop filling with water, and the water runs over the top, or out the front door and floods the laundry room, it’s probably an indication that there is a problem with the pressure switch, the water valve, or the hose that connects the pressure switch to the wash tub. Because house water supply pressure varies wildly depending on venue, and whether or not you are on a pump, or a city water supply, washing machine manufacturers had to find a way to ensure that there would be sufficient water in the washer to wash the clothes. They could not use a timing mechanism because in low water pressure situitions, it might not be enough water, and in areas with high water pressure, it may be too much water.

The solution was to use a closed pressure system that depends on the amount of water that is actually in the tub, regardless of the water supply pressure. All washing machines used in homes today, still rely on a water level control system designed years ago. So how does that work? And how does that relate to an overfilling washer?

Every washing machine has a water level control switch that uses air pressure forced through a small hose attached to an air bell on the washer tub, to control the amount of water that enters the machine. The water level control switch is usually located in the control panel of the washing machine, but can also be mounted somewhere else on the machine, usually near the top. As water enters the machine, air is forced into the air bell with the small hose attached at the top. The hose on the top of the air bell extends all the way to the water level control switch. When the air pressure in the hose is sufficient, based on the amount of water that is in the washer, a set of contacts in the water level control switch opens and disconnects the electrical path to the washer fill valve. And of course water stops entering the machine. Another set of contacts within the switch now complete a circuit to the washer motor, and the washing machine starts to agitate.