smelly washing machine

[cupcake]

Hi
My washing machine works fine ... but ... if I leave it empty over night, the next morning when I get up it has a couple of inches of smelly water in it! If I turn it to 'drain' - the water dissapears and I can do my washing as normal.
Why is this happening?

 

[cmother1]

If the W/M waste pipe goes into a spigot on your sink trap this is the most likely candidate. It's probable that the sink waste is partly blocked below the level of the spigot. Try hooking up the W/M waste pipe as high as you can under the work-surface so that gravity is on your side.

If your W/M drains into its own waste pipe the only possibility is mains water leaking through the inlet valve, but I wouldn't expect this to be smelly, unlike stuff originating from the sink.