Water Softener backflow issue

[Sard]

Hi,

I recently had a new water softener (BWT brand) fitted as part of a new kitchen. It's been working fine but I recently noticed the salt reservoir had very nasty and oily residue floating around it (looked like vomit at first) which could have come from the dishwasher or kitchen sink. I had requested my plumber to fit the discharge and overflow into same waste pipe that the kitchen and dishwasher feed into (see picture below). The water softener sits in a unit next to this pipework.

The softener had been working fine but I'm a bit puzzled as to why I had this backflow. My gut feeling is that the dishwasher went on late one night and the water softener also was on a regen cycle where back pressure may have pushed waste water into the softener. Downstream from the waste connection is also a hep vo waterless trap and I haven't noticed any blockages or slow running of the sink.

I've considered putting a check valve in here but it's awfully tight. Additionally, I'm now concerned that the water softener salt chamber has had contaminated water sitting in there and despite my best efforts to clean it out, I cannot get behind the resign tank and now I'm worried that if I turn my water softener back on, I could end up contaminate my water supply and worried that this softener is now unfit for use.

Any advice on how to move forward would be greatly appreciated.

Here are photos of the pipework
1) Waste connection (dishwasher and sink showing)



2) Waste connection (water softener overflow and discharge showing)


3) Water Softener unit (high flow in and out, overflow and discharge showing)

 

[JohnD]

The waste pipe from the softener is closed except when water under pressure is running out of it.

It's just about possible that dirty water could squirt up the overflow pipe if it was badly fitted and the waste was under pressure, for example by an appliance pumping into it.

I will guess your overflow is the white plastic pipe.

It seems to be sealed to the waste, which is wrong.

The overflow is supposed to be visible so you can see if there is a fault causing water to come out of it. Mine goes through the wall and discharges onto the ground.

You would to better fitting a standpipe with trap and airbreak.

Stand back and take a wider pic that shows the route of the pipes.

Did the installer read the fitting instructions?