bowl and a half kitchen sink waste

Hi, Sounds like you have a few faults with the way your sink waste has been fitted! Firstly bottle traps shouldn't ever be used on kitchen sinks, they're not designed for it as they get blocked up with food debris etc. It also sounds as though there isn't enough fall on the waste pipe (minimum 20mm per meter) your sink should also be connected to a MINIMUM inch and a half waste pipe and definately not inch and a quarter, when you empty a full bowl the pipe will be running at full bore creating a vacum behind it and sucking the water out of the other trap hence the smell coming up from the drains . It would be best to get a plumber in to do the job properly i.e re run the waste in the correct size pipe, bin the two bottle traps, fit a purpose made bowl and a half waste kit with a single P or S TRAP and appliance connection. Hope this helps Steve D2 Plumbing & Heating

potentially i would guess there is not enough fall on one of the waste traps or pipework but also i feel eliminating the small bowl trap and changing main sink trap to accomodate you will gain a better flow of water through waste hopefully eliminating smells.

The main problem you are having, is that the main pipework back to the stack, is undersized. It should be a minimum of inch and a half pipe. Once this pipe is upgraded it should remedy the syphonage problem, which is causing the other trap/traps to loose their seals. This is the cause of the bad smells coming back up from the drains, to remedy this problem shouldn't be too difficult, which is of course dependant on your current set up!

I agree with what's been said but I realise you might not want to go to a lot of expense so here's a tip. Pop into a plumbers merchants and ask for a Hep valve - it's a dry trap which is easily fitted onto the pipe run before it gets to the stack. Doesn't cure the bottle trap problem (blocking) but if you keep them clear with plenty of detergent and hot water you might be lucky. All the best Nigel

Is your waste level or does it have a fall built into it? I'd fit a non return valve into the pipe any way and think about upgrading to 40mm pipe Steve

Clean washing machine trap & check waste pipe into main stack. Or you could purchase a bottle of drain doctor from B&Q pour that directly into trap it should clear itself after a few minutes but. READ INSTRUCTIONS BEFORE YOU START............