Zanussi DW24 IWMU (tiredengineer)

Your diagnosis appears to be spot on as I have looked at the
IWMU bottle and can see that it is heavily silted up with hard
water sediment.I live in possibly the hardest water area of
the UK.Putting 2 and 2 together I can now see how this has
happened-With the introduction of the 2-in-1,3-in-1 and
then the 4-in 1 tablets we unfortunately stopped using the
salt but have lately realised that this is not a good idea as the
m/c does not give good results. Anyway, having 'tapped' the
bottle and moved the silt the m/c operated successfully over
2 cycles but the silt has now settled again and the problem
has reurned. Question,-I can see no way of removing the
bottle from underneath, does it release by undoing the large
plastic nut under the salt filler cap? I don't want to damage
anything.

The large plastic nut under the bottle cap does release the bottle, along with the valve, pipework and electrics. Not an easy job but it can be done, might be easier with a wet and dry cleaner, suck the stuff out of the bottle. If you're going to take it apart I'd suggest disconnecting hoses and cleaning them out too.
The best results with any dishwasher are achieved with the use of seperate powder, rinse aid and salt. (Salt should even be used in soft water areas).
I'm not sure what the makers think they are doing with 2,3 or 4 in 1 tablets as the salt used seperatley never gets near your dishes. At the end of the cycle salt water is pumped through the water softener unit to flush out the impurities. Before it does the next wash it takes in and pumps out water to get rid of the salt water and impurities.


Unplug your appliance before working on it.

tiredengineer

At last someone on my side!!!

Every time that b*****y advert comes on I cringe
How can they advertise salt in the tablet, this encourages the user not to put salt in the salt bottle in the dishwasher. As you quite rightly said when salt is put in the proper place it is used to backflush the water softener in the machine, the only time it gets anywhere near the dishes is when the salt solution has been through the water softener backwards, it runs along the bottom of the wash chamber into the outlet filter as it's pumped down the drain.
This advert alone must be reponsible for many water softeners in dishwashers getting blocked due to the lack of salt backflushing, this must be a case for the advertising standards authoroty