If a Washing machine fills and drains at the same time there are a few possible causes. The water could be siphoning down the drain due to an issue with the plumbing. The washing machine could be overfilling. Or the wash cycle could be aborting because it’s detected an overheating fault. Careful observation of where on the cycle the issue occurs will help to work out which of these different faults is causing the problem.
Is water quietly siphoning out or being pumped out?
If the water is just running down the drain but the pump isn’t running, jump to the “siphoning water” section below. If you can hear the drain pump running and the water is being pumped out then it could be aborting the wash. Don’t confuse the water pump with a recycling pump if fitted. You should know the difference between the drain pump that runs on rinses and spin and the recycle pump that runs on the wash cycle. Not all washing machines have a recycle pump.
Some washing machines are programmed to react to the water being overheated by pumping some away and taking in fresh cold water. It can get stuck in this cycle. However, it should also indicate some error code by flashing lights or lighting up specific option lights or displaying a specific error code if it has a digital display.
This fault could be caused by genuine overheating or a faulty thermistor (thermostat). The filling with water isn’t necessarily continuous, it may top up for a while, energise the pump, then repeat. However, I couldn’t say this would be the case for all washing machines. If you think you have this fault you’d be better finding an engineer but I have a general help article here – How to test an NTC thermistor.
If the pump is running continuously as soon as the washing machine is turned on and won’t shut off there could be insulation faults on the machine.
If water isn’t being pumped out, but just draining away all the time, the washer will keep detecting there isn’t enough water inside and top up with more. Modern washing machines should be sophisticated enough to realise something’s wrong and abort with an error, but if not, it may continue washing or rinsing for a short while before losing enough water to trigger more coming in again. It can get stuck on this cycle indefinitely and it’s called siphoning.
Siphoning occurs when the end of the drain hose is lower than the level of the water inside the washing machine. The diagram shows a correctly plumbed in washer where the end of the drain hose is higher than the level of water in the drum. Water always levels, so you can see the water in the drain hose matches that of water in the the drum. If the drain hose was pushed down much further, or the stand pipe it pushes into falls over then water can start to siphon out. Siphoning can start by the force of gravity or when water is first pumped out of the machine in much the same way as you siphon petrol from a car by sucking the pipe to start the liquid flowing. Remember: if the pump is running it is not siphoning.
This fault most often occurs when the washing machine has been moved out for cleaning or relocated in a new house etc. It can also occur if a drain hoses stand pipe isn’t properly secured to the wall and falls over at an angle. If your washer is plumbed into the u-bend under the sink you should be able to discount siphoning because the u-bend is clearly higher than the water level inside the washing machine by quite a bit.
When plumbed into a stand pipe the drain hose should have a plastic crook to force a shepherds hook at the end. This not only helps keep the drain hose from falling out but stops it being pushed too far down. The length of drain hose sticking out of the crook should roughly be about 4 or 5 inches.
This Drain hose crook is not required if the washer pumps into a connection on the U-bend under the sink although if it is, the drain hose should be tied up so that it goes up several inches before running down to the washing machine pump to prevent siphoning (see make sure there are no problems with the plumbing).
The height of the waste water pipe on the plumbing should be about 18 inches to 2 foot. Basically, the end of the drain hose should not be lower than the water in the tub. Full instructions for the exact height of the stand pipe should be available in the instruction book or on separate installation instructions.
If the washing machine overfills it should most likely trigger an error code but depending on how the drain hose is plumbed in overfilling can trigger siphoning too. The water level can be seen rising way above halfway up the door glass and eventually it may start to flood out of the back or out of the soap drawer. If this is happening to your washing machine then read washing machine is overfilling which deals with overfilling where water floods out of the machine as opposed to constantly filling with the water going down the drain.
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