my dishwsher drains but then water comes back, any ideas why?

[mk1975]

hi, my dishwasher is new, i got it 2 months ago, till last week everything was ok, now when cycle is finished its all dry, but after an hour or so i can see water on the bottom, around the filter. i've checked filter, its clean.
it doesnt do it after every wash, by the way, i unplugged it last night and there is no water, i've just checked again :)) i dont know if its coincidence, thank you.

[buildersmate]

This suggests that water from wherever the dishwasher drains to is finding it's way back down the dishwasher drain pipe to the sump of the machine.

If you have the dishwasher plumbed into the bottom the U-bend below the kitchen sink, you could test this theory by seeing whether this rogue water only appears after you have drained waste water from the sink above.

It is not necessarily a problem to the operation of the machine as when you restart the machine cycle, the first thing is does is to pump out any remaining water in the sump.

[mk1975]

thank you buildersmate for the quick reply, unfortunately its not under the sink,i will have to pull out the dishwasher and i wouldnt have a clue what to do,
would it be ok if i keep using the dishwasher for a month, i wouldnt want it to break down, my dad will be visiting me after christmas, and he is the best for repairs around my house :)

[buildersmate]

Where does the dishwasher drain to? - it is connected by a flexible pipe of about 40mm diameter, often grey in colour, to the drainage system of your house somehow. It is uncommon for it to be further than 2 metres away.

You do not need to pull the machine out - just find where the grey pipe connects in.

[mk1975]

it is about a meter away fom the sink but to get to it i need to pull out the dishwasher, its not directly connected under the sink :(

[The Builder]

Perhaps the 40mm waste pipe runs across the wall behind the machine. There may be a trap (u-bend) here for the waste hose to slot into. Possibly, the entry point of the hose is too low causing syphonage back into the machine.

Is there one of these? ...........

http://www.screwfix.com/p/washing-machine-trap-40mm/18640

[factor-fiction]

Although the dishwasher may be a metre from the sink does the grey pipe buildersmate refers to not come out under your sink to join the sink drainage system?

[BRIGHT SPARK]

The water cannot syphon or drain back into the machine unless the drain solenoid is faulty...if the machine is a few years old it could be a scale buildup that restricts the solenoid movement...

[BRIGHT SPARK]

Forget about the limescale bit...just read the post... its almost new.

[mk1975]

Thanks for your replies. Yes it is like buildermate said. I will have a look underneath sink, dont want to ask the husband to have a look.
Do u think its ok to operate dishwasher in meantime. Thanks.

[buildersmate]

Good-o, now we are getting somewhere.
The famous grey pipe perhaps approaches the exit point into the U-trap (whatever) from below? - rather than from above? - in which case I think it is perfectly feasible that waste water out of the sink going back down the famous grey pipe and into the D/W sump.
Bright Spark (who undoubtedly knows a lot about these things) reckons there is a solenoid (a valve) on the outlet of D/Ws - there isn't on mine, so it can happen.
No, it isn't a problem, but have you done my suggested test to see if there is a correlation between the dumping of water down the sink and the sudden apperance of water in the sump?

[Clanad]

Buildersmate most likely has the correct answer to your problem... but on the other hand, if the sink is also equipped with a waste disposal (the one that you turn on a switch while running water into the sink to grind up those pesky potato peelings)... it'll be directly under the sink and is a cylinder about 5 or 6 inches in diameter and perhaps 8 inches long.

The next time you have water remaining in the dishwasher, turn on the disposal unit for a little bit and then restart the dishwasher near the end of it's cycle to see if all the water is expelled and stays expelled. If the disposal has a lot of junk in it, the waste water from the dishwasher won't drain through it very efficiently... and can leach back into the dishwasher, since, in a lot of cases (at least here in the U.S.) the waste water from the dishwasher goes directly into the drain pipe from the sink above the disposal, whereas the "gooseneck" or U shaped trap the others refer to is below that disposal...

[mk1975]

hi, sorry, was out with kids, yes i had a look, had to pull diswasher a little bit, it comes from below like buildersmate said, but for some reason the famous grey dishwasher wee pipe is connected to a grey pipe, underneath my combi boiler.
i'll just keep using it till my dad gets here, so far my unplugged dishwasher doesnt have any water at the bottom, i'll keep it unplugged when im not using it, many thanks or your helpfull replies. good night