What Causes a Washing Machine to Overflow?

flooding washing machine
  • 3 hours
  • Intermediate
  • 150
What You'll Need
Pressure switch or
Water inlet valve
Mop or rags
Dry-Wet Vacuum cleaner
What You'll Need
Pressure switch or
Water inlet valve
Mop or rags
Dry-Wet Vacuum cleaner

A washing machine is the one piece of equipment in the house that everybody absolutely needs at least on a weekly basis. Most problems associated with washers show up after they're filled with water, when the appliance stops in the middle of a cycle and simply refuses to do any more. Usually caused by an electrical or mechanical malfunction, this issue often ends up with someone having to drain the water out by hand. With this misfortune, the only thing affected is someone’s patience.

A different situation sometimes occurs, with a totally different outcome, when a washer starts leaking water from a faulty water hose, solenoid valve, pump, drain hose, leaking tub, clogged drainpipe, defective pressure switch, or pressure hose.

The following procedure is for the second situation when a washer tub overfills and completely runs over (Figure 1), immersing the flooring, and seeping into the basement if caught too late.

washing machine basin and controls

Step 1 - Secure the threat

The first thing to do when walking into a laundry room flooded with water is to shut off the appliance by pushing in the cycle dial button (Figure 2) to remove the power from all valves, relays, and timer switches.

Step 2 - Listen and Observe

With the power turned off, if the water can still be heard coming in, close the water shut-off on the other side of the machine (past the leak, toward the water supply source).

Step 3 - Solenoid Valve or Pressure Switch

washing machine wiring

If the washer is filled to the rim and running over, the problem is with either one of the ganged solenoid water inlet valve (Figure 3) or the pressure switch (Figure 4). The way the two are interconnected is that the the load size switch, being a pressure switch, routes current from the cycle switch to the temperature switch and the water inlet solenoid valve.

The pressure of the water in the tub is transmitted to the load size switch through a clear hose connected at the bottom of the tub in Figure 5, running all the way up to the pressure switch where it's connected in Figure 6.

washing machine valves

This is designed to activate a diaphragm that transfers that pressure to an SPDT (single pole double throw) switch in figure 7. When triggered by an appropriate amount of pressure, this switches the current flow from terminals A and B connected to the solenoid valves to terminals A and C, which connects to the motor to initiate the washing cycle.

washing machine pressure switch

With that explained, it’s easy to realize that there are only two components that can be at fault for an overfill problem.

Step 4 - Getting Access to the Controls

The next step is getting access to the valves and controls. A washer is usually quite easy to take apart to get inside. In the Whirlpool model in Figure 8, it's plain to see that only four screws are used to keep the control panel and the back panel together with the rest of the washer. Two large clips are added to hold everything in place at the top, and two more screws (not shown) connect the bottom. The rest of the assembly is mounted with lips and tabs.

diagram of washing machine interior

Screws and attachment brackets should be easily found in the back of any washer to take it apart. It’s mostly always designed to be an easy task.

Step 5 - The Ganged Solenoid Inlet Valve

If the water inlet valve is stuck opened or partially opened due to an obstruction, mineral deposits, or a faulty compression spring, it can be determined by pulling out the electric cord from the outlet to completely remove any electrical possibilities. Both the hot and cold water taps can then be turned back on and off briefly, in turn, to listen if the water can be heard coming in. If this is the case, the valve must be replaced as in step #6, if not, the next step is #7.

Step 6 - Replacing the Water Inlet Valves

This is an easy task requiring only a screwdriver and pliers. the hoses from the hot and the cold water need to be removed from the valves, then, the three clamps holding the short pieces of hose inside need to be removed also, using the pliers. The valve assembly can now be taken out by unscrewing it from the back panel and replaced.

Step 7 - The Load Size Pressure Switch

With the possibility of a defective water inlet valve now ruled out, and since the power going to it comes from the pressure switch (as described previously), it can be assumed that the pressure switch is likely failing to switch the current flow from the solenoid valve to the motor. Here are four possible causes:

1. Obstruction at the plastic hose could be preventing the compressed air from reaching the switch.

2. Rupture of the plastic hose could be causing pressure to build up.

These two can be easily verified by removing the hose and blowing in it to see if the air goes through, then while squeezing shut at the other end to check if it’s ruptured or punctured.

3. Internally, the diaphragm inside the pressure switch could be ruptured or leaking, preventing the pressure from building up.

4. The compression spring or some other internal mechanical component might have failed inside the pressure switch, leaving the amount of pressure coming from the pressure hose insufficient to trigger the switch-over.

Step 8 - Replacing the Pressure Switch

This is also easily achieved by first pulling out the small pressure hose from the side of the switch.

There's a small tab on the switch right up against the front panel that locks it in place. The tab is pushed in, releasing the switch which can then be rotated 1/8 turn to the left, permitting it to be pulled out, after the knob is pulled off it from the front.

The new switch can now be installed following the same procedure in reverse order.