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Siemens dishwasher - drains but not fully

Can’t remember the configuration behind the machine (guess I’ll soon find out!) but does connect into the sink drain. Whatever it is, it’s been perfect for 12 years.
Our Siemens dishwasher drains into the same waste as the sink and washing machine. The sink was draining OK, likewise, there were no issues with the washing machine. I had to sponge out that last bit of water from the bottom of the dishwasher before it would run (it came up with a fault code, can't recall which one). In the end, I used one of those rotary drain unblockers up the pipe from the outside drain & released a mini-fatburger. Then all was well.
 
It is, but it is as dangerous as a strong acid, I suspect many think only strong acids can burn and dissolve.
So treat it like a strong acid and be safe..
I know, I remember we had pellets of the stuff in the labs at university. You ended up with the same holes burned in your jeans and the same pain as it ate into your skin!
 
Our AEG dishwasher has a flood switch which had the same symptoms OP and with that machine you have to lie it on it's back then put it upright and it works, ours is semi-integrated.
 
OK, I’ve taken the traps etc apart and cleaned thoroughly. Some crud in there but not enough to cause a problem I wouldn’t have thought. Blown down the dishwasher drain pipe, little resistance and bubbles away in the filter housing. You can see the waste pipe in the first picture which loops up over the wooden block and then into the sink trap in the second picture. I’m running another cleaner / hot wash through it now then see what happens. If it’s still the same, I’d have thought the pressure switch is next on the list. It’s not worth throwing money at a 12 year old machine but if I can solve it myself then great. Thanks for all the ideas!



 
Is there a filter in the “cone” that the dishwasher waste pipe pushes onto at the side of the waste trap?

I seem to remember this blocked on ours.
 
Is there a filter in the “cone” that the dishwasher waste pipe pushes onto at the side of the waste trap?

I seem to remember this blocked on ours.

No filter on there. There was a bit of crud but cleaned it up. Doing its thing at the moment so I’ve gone to listen to some tunes!
 
Caustic Soda.

Way cheaper, more convenient and safer - use cheap bleach - the thin stuff at about 40p per 2 litre can.
Although bleach (sodium hypochlorite) is actually acidic, it decomposes reasonably fast, so in liquid bleach they stabilise it with sodium hydroxide, so houseold bleach is markedly alkaline. It works fine to clear fatty deposits, what it won't shift is iron stains (which is what the water round here leaves).

Our AEG dishwasher has a flood switch which had the same symptoms OP and with that machine you have to lie it on it's back then put it upright and it works, ours is semi-integrated.

Almost certainly the pressure switch blind pipe getting air-locked by water gradually getting sucked up it. Flipping it on its side would allow it to drain and work properly again.

Pedantry - "strong" acid etc. as keeps getting used here, means precisely nothing in the way in which is used. Acetic acid is a weak acid, but I'd not recommend bathing in it.
None of these things are dangerous, the dangerous bit is the wally using them.
 
After the hot wash and cleaner yesterday, there was a bit less residual water in the filter area. I didn’t sponge it out (deliberately) but have just put on a quick wash. Stopped after a minute. Sponged out (really not that much water) and now running fine. It can’t be the water supply or drain (unfortunately). The pressure switch is looking a distinct possibility. Going to have to consult YouTube videos and pull the damn thing out when I’m in the right frame of mind and keep using the sponge in the meantime.
 
The pressure switch is looking a distinct possibility.

Sadly, if it is broadly similar to the one here, I can think of no way of avoiding stripping it.
It might be possible to clear it, if that is really the problem, by long and laborious cycling with hot caustic - far longer than getting to the switch and clearing it by hand. Just hope that that is the fix.
 
We mainly use the quick wash after rinsing everything off in the sink. I’m thinking because it’s not often run very hot...

Our Siemens dishwasher heater failed after 13 months. It had clogged up and overheated. Replaced under warranty.
The engineer asked me what powder and settings we were using: "separate powder, salt and rinse agent. Default "Eco" setting. Exactly as it says in the manual"
The engineer told me to ignore the manual; use the combined pills and avoid Eco setting like the plague!

It has been fine since then.

I would recommend giving it a blast on the hottest setting every couple of weeks!
 
On our Bosch dishwasher there is a flow meter monitoring the water entering the machine. It’s a paddle wheel with a magnet embedded in to it and an adjacent reed switch which operates every revolution of the wheel. The switch went intermittently faulty so too much water was brought in during the wash cycle and then didn’t all pump out in time afterwards. This brought the water alarm LED on. It’s another possibility. Think the switch cost about £15.
 
When you start any programme, does it run the drain pump before trying to fill? This is the normal procedure for every dishwasher I've ever owned or fixed (ex Miele engineer).
 
Ours did this. It turned out the the filter in the well had a fine film of fat that was preventing the water drainind. 9nce this was a washed in hot water and detergent it was fine.
 


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