We had a new kitchen fitted four years ago. The sink is a double drainer (small and larger sink), and the dishwasher and washing machine are plumbed into the same waste pipe below the sink, which has caused a gurgling sound ever since (a reliable plumber told us that the way it has been plumbed is the cause of the gurgling).
Recently, there has been a really bad smell (like rotten cabbage) coming from the kitchen sink drain, so we used this as an opportunity to take all of the plumbing apart underneath the kitchen sink to clean it and fit an anti-syphon trap, hoping that this would fix the gurgling and the smell.
When we took the plumbing apart, the pipes were all reasonably clean and there was plenty of water in the U-bend, which was not what we were expecting to find, given the bad smell.
Now the anti-syphon trap has been fitted, there is no more gurgling; however, the bad smell it still happening!
For reference, there are no pipes or drains on the outside of the property.
Any ideas what is causing the smell please and how we can fix it?
