Smelly kitchen sink and cupboard

[6strings1song]

In the hot weather we have noticed an earthy cabbagey damp smell emanating from the area of our kitchen sink. Last year when we went away for 2 weeks we came home to a cabbage smell as soon as we opened the front door. We repeatedly chucked loads of boiling water and bleach down the sink and that seemed to solve it after a week, but the weather quickly turned cooler and the smell went.

Now the hot weather has returned and the smell is back. So far I have tried...

• Soda crystals down the sink mixed with boiling water on two occassions
• Boiling water alone and with bleach.
• Soda crystals round the washing machine (just in case it was from there)

However, nothing is budging it. Today in desperation I unscrewed the plug mechanism and discovered a load of horrible brown/black grime and old fat. 🤢 I have cleaned this all out, wiping out the entry to the overflow etc. I made sure a bucket was under the sink and caught any drips. Screwed everything back together tightly and followed up with a chaser of boiling water. Thought that would solve it....

The smell is now even worse! 😭 It seems to mostly be coming from under the sink. The plug mechanism is screwed back on tight and no leaks. We can't see any other pipes leaking, cupboard is dry, no mold and used to store cleaning stuff (no food).

Any ideas welcome and gratefully received! I can only think to try taking off the u-bend and cleaning that out, but I would have thought the gallons of boiling water and soda crystals would have solved any issue there.

Disclaimer...we have only lived in this house 2 years and don't put fat or oil down the sink. The previous owners seemed loved a fry up...judging by the disgusting greasy state of the top of the kitchen cupboards when we moved in, so definitely blaming them for any lingering nasties. 🤨

Sometimes you need to slowly run water into the traps under sinks etc to stop drain smells coming up through the pipes.

Have you cleaned the drain grate where the water goes through outside , just a thought but if that is covered in fat and grease the smell might be coming back up from there.

You need to take the u-bend off and also clean the drain outside

Break up dishwasher tablet and put the power down sink. Will help dislodge fat

There’s the possibility you have an anti stench trap on your outside drain, if so it might be in the open position allowing smells to come up into your kitchen. Had a new kitchen fitted and the kitchen fitter told us about it. It needs closing off from outside, Google how to do it.