Dishwashers bought from John Lewis (model number JLBIDW1200) which are manufactured by NEFF, display error codes in the digital display. If 20 appears in the display (red LED) it means there is a problem with draining the water.
This should however be fairly obvious without an error code as the dishwasher should be full of water. It is possible that it’s only partially drained out the water though, so check under the main pull out filter in the base just under the lower spray arm.
If you are getting the 20 error code but there is no water inside the dishwasher it may be caused by a fault on the system that reports the presence of water inside the machine. In this situation I would call in an engineer – finding an appliance engineer.
If the dishwasher is full of water
Draining a dishwasher full of water can be tricky because ideally you need to remove or disconnect the drain hose at the back and lower it into a bowl. However, dishwashers can be difficult to pull out especially if full of water. The extra weight can contribute to damaging the flooring too. You can of course ladle the water out. Remove the lower basket and start scooping with an appropriate vessel.
Once most of the water has been removed you’ll find at least a few pints more underneath the main filter in the base under the lower spray arm. Just pull it out to get at it. At this stage I’d consider using a few large towels to soak it up.
Possible causes of dishwasher full of water
Once most of the water has been removed you have to consider what the problem is. Dishwashers can be difficult to work on so I don’t advise delving too deeply. Most parts are in the base of the machine with no back panel to remove to get at them. Some need the lid, and side panels and kick strips etc. all taking off to get to parts. Do not turn a dishwasher upside down.
One of the most likely causes is a blockage somewhere although the pump could have failed. Things I would try before calling in an engineer are removing the drain hose from the u-bend connection under the sink (if that’s how it’s connected) and checking inside the plastic spigot at the end of the drain hose and inside the plastic connection on the u-bend for obstructions. Also, remove the big filter in the base (under the spray arm) and carefully check for obstructions in the channel leading into the drain pump.
Possible culprits are bottle tops, bones from chickens etc. and broken glass, all of which can get under the filter if it isn’t seated properly at any time. It should be impossible for anything large to get past it if fitted and seated properly though. Remember, broken glass is dangerous! I’ve seen quite a lot of large sharp pieces of broken wine glasses for example so do not go poking around recklessly with fingers.
If none of these produce any results then investigations into whether the pump has any connection or power supply issues, or has gone faulty need investigating. Unless prepared to start stripping things down I would call in an engineer – finding an appliance engineer.