If a Washing machine fills with water and drains it away at the same time there are a few possible causes. This unexpected behaviour can get the washing machine stuck in a vicious cycle. The water could be siphoning down the drain due to an issue with the plumbing. Or it could be aborting the wash program because it’s detected a 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 Draining Out or Being Pumped Away?
The first thing to establish is how the water is leaving the washing machine as it tries to fill up. If the drain pump is definitely not running, but water is being lost down the drain then it must be siphoning. See my in depth explanation of siphoning later in this article.
Water is being pumped away
If you can hear the drain pump running, and the water is being pumped out just as it does at the beginning of the spin cycle, then it could be aborting the wash. Don’t confuse the water pump with a recycling pump (if fitted). They just recirculate water back into the drum.
Could be Overheating
Modern washing machines detect and react to the water being overheated. They can start pumping the hot water away. They may simultaneously take in cold water to cool everything down. If this is what’s happening it should also indicate an error code by flashing lights or lighting up specific option lights or displaying an specific error code via a digital display.
If overheating is the cause of this fault it should happen on the wash cycle. It should also happen after at least half an hour or so when the water has heated up. You should also be able to see that the water inside is very hot. I would also expect this behaviour to be relatively short lived. If the washing machine thinks it has overheated and has aborted the wash cycle, then all it needs to do is cool things down and pump away all of the water. Once this is done it should turn off displaying an error code.
This fault could also be caused by a faulty thermistor (thermostat) giving false readings. 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 runs continuously as soon as the washing machine is turned on and won’t shut off there could be insulation faults on the machine. Call an engineer.
If water is just draining away all the time but not being actively pumped out, this is siphoning. The washing machine is trying to fill the drum with water, but water is being lost down the drain. It 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. If not, it may get stuck in this cycle indefinitely.
Siphoning occurs when the end of the drain hose is lower than the level of the water inside the washing machine. My diagram shows a correctly plumbed in washing machine. 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 the waste water pipe much further, or the 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. The latter happens in the same way as you’d siphon petrol from a car, by sucking the pipe to start the liquid flowing. Remember: if the pump is running it is not siphoning. Also, siphoning is not likely if the drain hose is connected to the u-bend under the sink because it’s so high up.
Has the Washing Machine Been Moved recently?
Siphoning 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 stand pipe isn’t properly secured to the wall and falls over at an angle.
When pushed into a stand pipe the drain hose should have a drain hose crook 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.
Full instructions for the exact height of the stand pipe should be available in the instruction manual, or on separate installation instructions that came with the machine.
If the washing machine overfills it should not simultaneously fill with water. However, if the end of the drain hose is in a standpipe, and low enough, it could trigger siphoning. Water can start to flow out of the drain hose and down the drain caused by the higher level of water in the drum. The washing machine detects the loss of water and keeps filling. This would be rare though. If the siphoning wasn’t triggered, the washer would overfill and flood. If you can see the water levels in the drum are way too high and your washing machine is definitely overfilling try here overfilling.
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