Fix a leaking sink trap or waste pipe

Use this guide when you find water in the cupboard under a sink, a swollen cupboard base or a musty smell. It covers the plastic waste pipework below the plughole, not the water supply pipes or taps. Have a bowl, old towels, a torch, kitchen roll, plumber's silicone or a new washer, and possibly a replacement trap ready.

Step by step

1. Work out whether it is waste or supply

   Empty the cupboard and dry everything. Run the tap without the plug in for a minute and watch with a torch: drips that only appear while water drains are from the waste side and this guide applies. If the pipes drip when the tap is off, the leak is on the water supply or tap connections; turn off the isolating valve or the stopcock and consider a plumber.