This happens when the top of the drain hose is lower than the level of the water inside the washing machine. It’s similar to siphoning petrol from a car tank. If the drain hose is too low, then water can siphon out as soon as it enters the washing machine. If it’s just slightly lower than it should be, then siphoning is usually triggered when the washing machine first pumps water out on a rinse cycle(higher level fill) or even just occasionally.
This mostly happens when the washing machine has been pulled out for cleaning . It can also happen if a drain/wavin wall pipe stand pipe isn’t upright, or, falls over at an angle.
The drain hose shouldn’t be pushed down too far down into the wall waste water pipe, which can cause the water from the washing machine to siphon just the same as if the wall pipe is too low. It needs to go just far enough in – 4-5 inches/100mm-125mm - to prevent it falling out but it will fall out if not secured properly with a hook or tape. If the wall pipe that the drain hose is being pushed into is too low, then it may need rising up. If it was just installed too short, you can add a small extension piece.
You should ensure that the plastic hook supplied with the washing machine is fitted to the end of the drain hose. The length of drain hose sticking out of the hook should be approx. 4-5 inches/100mm-125mm If the plastic hook is missing, Tape the drain hose in/leave an air gap to prevent it siphoning again.
