Old 1st Apr 2021, 23:08
  #2 (permalink)  
M.Mouse

Controversial, moi?
 
Join Date: Oct 2000
Location: UK
Posts: 1,595
Problem 1: Not unusual to have this sort of drainage problem.

My sister's softener is under sink in a utility room with the waste outlet from the softener discharging into a vertical pipe with a trap lower down the pipe. the problem was that if a sink full of water was emptied it would sometimes back up the softener stand pipe drain and overflow into the cupboard. I solved the problem by an arrangement similar to this crappy drawing:
To explain the drawing: I put a 40mm tee in the outlet from the sink and connected a P-trap to that tee piece. On the upright pipe connected to the trap I put another tee with a hose adapter to which I securely fastened the softener outlet with a jubilee clip. I extended the upright pipe and fitted an Air Admittance valve This allowed air in when the softener was discharging but prevented water from the sink backing up through the softener trap and, previously, overflowing from the softener fixed pipework. It works well. You will need to hunt around to find suitable fittings but they are all available.

Bear in mind a source of unsoftened water for drinking should be available. I dislike water softeners in cupboards under sinks purely due to the awkwardness of filling with salt. Unless you have purchased a block salt machine in which case you will pay an arm and a leg for the convenience of block salt. My softener is in my garage.

Problem 2: Providing the cupboard is well made and fitted I can see no problem in cutting out a suitable opening in the shelf to accommodate the softener. Care and planning would be needed to avoid making the cupboard look like it had been butchered!

Where in the UK are you based?
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