My daughter lives in a smallish flat and has just had a new bathroom fitted. The bathroom is adjacent to the kitchen and presumably uses the same waste pipes. Whenever she empties (for example) tea leaves / coffee grounds down the kitchen sink there is a gurgling noise and some of the kitchen waste appears up through the bath plughole. I know one answer is to use teabags / coffee bags but this doesn't address the root cause of the problem. Is there some form of one-way valve or trap that can be inserted somewhere in the waste pipe run to stop this happening?
Don, (great name ), It certainly wasn't a qualified plumber who carried out this recent work. Get the installer, or main builder / contractor back and instruct them to carry out the remedial work asap.