Dishwasher appliance trap capped with clingfilm!

[m40r]

This is a weird dishwasher plumbing question. A Neff dishwasher that was here when we moved in just started not draining at the end of the washcycle - i.e. standing water in the base. It only happened on the four longest cycles not the 30 minute quick wash option. So I checked the obvious stuff: 1) jetwashers not blocked; 2) filters clean and not blocked; 3) drainage pump cover unscrewed and no visible blockages, with "fins" able to turn round when pushed with a finger. 4) machine "reset" option invoked.

Next checked the drain house for kinks or compression. No visible problems and in any case wash cycle 1 is draining. Final step was to look for blockages in the hose itself. The hose is pushfitted onto a standard appliance trap like this one . Rather than disturb the pushfit I simply unscrewed the compression fitting to the pipe connecting the sink to the u bend. Now I'd noticed that pieces of clear plastic clingfilm could be seen pushing out from the compression fitting but I assumed this was just to stop any slight leaks through the thread.

But no, instead there was a sheet of clingfilm stretched over the male fitting and completely covering the pipe, held in place when the connection is screwed back on. I checked very carefully and there is no visible cut or gap for the water to exit!

I've taken it off and refitted the hose to the appliance trap but the same problem is happening.

However my question here is whether anyone can explain why the clingfilm was there and how the water was passing through? Is it some sort of plumber trick? I couldn't see any tears in the clingfilm - maybe it was fitted to stop debris from the sink falling back into the dishwasher hose? And maybe invisible pin hole punctures allow enough water though to drain the dishwasher under pressure?

 

[oldbutnotdead]

It'll have been some sort of bodge by previous occupants to disguise a problem of some sort.
Assume the whole setup is fubar, start by checking that the sink drain flows freely and take it from there.
Does the hose from the dishwasher have any sort of drop into that waste fitting (500mm min is usually advised to prevent the dishwasher backfilling from the sink)

 

[m40r]

Thanks for the input. The sink drain flows freely. The drain hose enters the sink cupboard unit at low level and rises to the appliance trap but I can't see if the rest of the hose behind the dishwasher is raised before dropping as it's an integrated dishwasher in a rented property. But it does indeed sound like a bodge done in the past to stop debris from the sink dropping and blocking the drain hose. I'll see what the call out engineer says but was in the meantime intrigued as to how the hell the water was draining away. At least it does not sound like a trade secret!

 

[oldbutnotdead]

If its a rental and the landlord owns the dishwasher then its their problem to fix (long as you've done the basic maintenance checks incl raking out the internal filter). Thinking on, the clingfilm might have been chucked in there due to an absent dishwasher and not removed when the dishwasher returned.