Match what you notice
- Only one sink drains slowly
- If the other outlets work normally, we usually start at the sink outlet, the trap underneath and the pipe serving that sink. Tell us whether the water has stopped draining altogether.
- Water comes up in the second bowl
- Some double sinks share a trap or waste pipe. If emptying one bowl sends water into the other, the restriction may be beyond the point where the bowls join.
- The sink backs up when the washing machine drains
- The appliance and sink may connect to the same waste. Tell us if the sink only backs up during an appliance cycle or also drains slowly on its own.
- The basin gurgles or fills when the bath drains
- We trace where the pipes join and inspect the common branch. After clearance we test the bath and basin separately and then together. If the fault returns, we look for a remaining obstruction, sag or poor fall where the pipe can be inspected.
- Several fittings back up or an outside gully overflows
- The restriction may be further along the drainage route. Tell us which fittings are affected and whether neighbours have noticed the same problem. Those details help locate the problem and establish who should investigate it.
When to contact Southern Water
A private drain serving just your property within its boundary is usually the property owner’s responsibility. Southern Water can help identify whether an affected drain is part of the public network. If neighbours are also affected or you suspect a public sewer is overflowing, use Southern Water’s reporting service.
What to tell us without running more water
If water or sewage is backing up, stop using the affected fittings and connected appliances until the problem has been assessed. Keep children and pets away from sewage. Tell us where the water appeared, whether the problem has happened before and whether any drain cleaner has already been used.
Further reading
- Report a blocked or flooding public sewer to Southern Water
- Southern Water guide to drainage responsibilities
- McAlpine example of a shared double-bowl sink waste