Water under a kitchen sink can come from several places, including a loose or worn waste joint, a weeping tap connector or isolation valve, a leaking appliance hose, or water running down from the worktop. Because the cupboard collects drips from all of these, the puddle alone does not show which part is at fault.
Finding the source takes a few simple checks. It is worth doing soon, as cupboard bases can swell and stain quickly.
The Most Likely Sources
The waste system carries water away from the sink. It includes the waste fitting in the plughole, the trap and the pipe running to the wall. Its joints rely on washers and seals that can loosen or perish, and they tend to leak while water is draining.
The supply side brings water to the tap. Flexible connectors, isolation valves and pipe joints are all under mains or stored-water pressure, so a fault here may drip all the time, even when nothing is being used.
Washing machines and dishwashers often connect under the kitchen sink too. A loose drain hose or a worn supply hose can leak into the same cupboard.
Water That Is Not a Plumbing Leak
Not every wet cupboard means a leaking pipe. Water can run off the worktop through gaps around the sink edge or the tap hole. Splashing during washing up can find its way below over time.
Cold pipes can also gather condensation in a warm, steamy kitchen, which may drip onto the cupboard floor. This usually shows as fine beads of water along the pipe rather than a drip from one spot.
How to Narrow It Down
Empty the cupboard and dry everything. Lay dry kitchen roll on the cupboard base and wrap small strips around each joint and connection.
First, leave the sink unused for a while and check the paper. Wet paper at a supply connection points to the pressurised side. Then fill the sink, pull the plug and watch the waste joints as it drains. Wet paper there suggests the waste.
Do not over-tighten plastic waste nuts, as they can crack. Never force a stiff valve, and avoid taking apart connections that are under pressure.
If water is coming out quickly, turn off the isolation valve under the sink if it moves easily, or use the stopcock, and put a bowl under the drip. Keep the cupboard door open so the area can dry out.
Getting It Repaired
Many sink leaks are fixed by replacing a washer, seal or connector rather than the whole sink. The right fix depends on the part involved and how easy it is to reach.
If you have found water under your sink and cannot trace it, our sink repair service in Oxford can check the waste, supply and connections and repair the part that is letting water escape.