Quick answer: A bathroom tap that drips after it is fully turned off often has a worn or damaged cartridge, washer, O-ring or valve seat, though debris and installation problems can also cause leaks. The exact part depends on the tap design. Check whether water is coming from the spout, handle or base, turn off the supply before inspection, and use model-specific repair guidance.
A slow drip can waste water and leave marks around a basin, but the visible drop does not always reveal the cause. A tap may leak from the spout when closed, seep around a handle while running, or leave water under the basin. Each symptom points to a different area, and a repair part from one tap may not fit another model.
This guide explains common causes of a dripping bathroom tap, the checks you can safely make, and when it is better to call a plumber. It is a diagnostic starting point, not a universal repair manual. Always confirm the tap model and follow its manufacturer’s instructions.
First identify where the water is coming from
Dry the tap, basin and cabinet, then observe the leak without forcing the handle. Note whether the drip continues from the spout when the tap is off, appears around the handle only when water is flowing, gathers at the base, or comes from a connection below the basin. A paper towel can help reveal a small leak around a joint.
Also note whether the leak occurs with the hot side, cold side or both. If water appears under the basin, check for a wet supply hose, connector, waste fitting or water that has run down from the tap body. Turn off the angle valves before touching pipe connections. If a valve is stuck, corroded or leaking, stop and contact a plumber.
Common causes of a bathroom tap dripping
Worn cartridge or valve component
Many single-lever taps use a cartridge to control flow and temperature. A worn, scratched or damaged cartridge can allow water to pass even when the handle is off. Manufacturer troubleshooting guidance from Moen lists damaged cartridges, O-rings and grommets among general causes, while Delta’s repair instructions for certain two-handle faucets identify worn seats and springs as possible causes. These designs use different parts, so do not apply one brand’s repair steps to another tap.
Damaged washer, O-ring or seal
Older or particular tap mechanisms may use washers or seals that flatten, crack or shift over time. A damaged seal can cause a drip from the spout or a leak around the handle or base. The repair part must match the tap’s model and construction. A generic washer that appears close in size may not seal properly.
Debris or mineral deposits
Small particles in the supply can interfere with a cartridge or valve seat. Mineral deposits can also affect aerators and moving parts, especially where water is hard. A restricted aerator usually causes uneven or weak flow rather than a leak when the tap is off, but debris inside the valve may contribute to a drip. Cleaning should follow the manufacturer’s guidance; aggressive tools or chemicals can damage the finish and seals.
Loose or damaged connections
Water under a basin may come from a supply connection rather than the tap’s internal valve. A hose may be loose, a seal may be damaged, or the leak may come from the waste assembly. Do not overtighten a fitting to stop a leak. Excessive force can crack a connector or damage threads. Identify the exact source and use the correct replacement seal or professional repair.
High water pressure or a failing shutoff valve
Pressure and shutoff problems can make a small defect more noticeable or complicate repair. If several fixtures drip, pipes knock, or a tap leaks even after its local valve is closed, the issue may extend beyond that fixture. A plumber can assess the pressure and valve condition. Do not make system changes based only on a drip at one tap.
Checks to make before arranging a repair
- Record the tap details: Look for a brand name or model number on the tap, receipt, box or installation paperwork. Photograph the handle, spout and any visible leak.
- Locate the leak: Confirm whether it is at the spout, handle, base, hose or waste connection. Dry surfaces first so old water does not mislead you.
- Check the local shutoff valves: Learn which valve supplies hot and cold water. Turn them gently only if they move normally. Do not force a seized valve.
- Notice the pattern: Record whether the drip is constant, happens only after use, or changes with the hot or cold handle.
- Keep parts together: If a qualified repairer removes a cartridge or seal, retain it and the tap model details so the replacement can be matched correctly.
When is a simple cleaning enough?
If the issue is limited to a dirty aerator or visible mineral buildup, cleaning the removable aerator may improve the flow pattern. Shut off the tap and follow its manual for removal. Protect the finish with a soft cloth and use only cleaning methods approved for the material. Do not assume that cleaning an aerator will fix a spout that continues to drip when closed; that symptom may come from the internal valve.
Take care with plated, coated or coloured finishes. Abrasive pads, strong acids and harsh cleaners can leave permanent marks. For a removable part, confirm the manufacturer’s cleaning advice before soaking it. If you cannot identify the part or the tap design, ask a plumber or the manufacturer for guidance.
When should you call a plumber?
Call a qualified plumber if the leak is under the basin and you cannot identify its source, a shutoff valve is stuck, the tap body is cracked, water is reaching cabinetry or walls, or the repair requires opening the valve and you are unsure how it is assembled. Professional help is also sensible when the tap is under warranty or replacement parts are difficult to identify.
If you do inspect a tap yourself, shut off both supplies first and open the tap to release trapped pressure. Cover the basin drain so small screws do not fall into it. Work only from the exact model instructions and avoid forcing components. After reassembly, open the shutoff slowly and check for leaks while the tap is both off and running.
Repair or replace the tap?
A repair may be suitable when the tap body is sound and the correct cartridge or seal is available. Replacement may be more practical if the body is cracked, parts are no longer supported, corrosion is extensive, or the tap has recurring leaks. Consider the condition of the basin holes, supply connections and available clearance before choosing a new model.
Do not replace a tap only because its handle feels stiff. Mineral buildup, a worn cartridge or an installation issue may be repairable. Conversely, repeatedly changing seals without confirming the cause can waste time and leave the underlying problem unresolved. Ask the plumber to identify the failure and confirm the compatible part or replacement model.
Frequently asked questions
Why is my bathroom tap dripping when it is turned off?
A worn or damaged cartridge, washer, seal or valve seat can let water pass after the handle is closed. Debris may also interfere with the valve. The correct diagnosis depends on the tap model.
Can a dripping tap be caused by hard water?
Mineral deposits can affect aerators and internal components, but hard water is not the only possible cause. A persistent drip may require a compatible replacement cartridge or seal.
Should I tighten the tap handle to stop a drip?
No. Forcing the handle can damage internal parts and does not repair a worn seal. Close it normally and investigate the cause.
Why is water leaking under my bathroom basin?
Possible sources include supply hoses, shutoff valves, tap connections and the waste fitting. Dry the area and observe the leak, but shut off the water and call a plumber if you cannot identify it safely.
Can I replace a tap cartridge myself?
Only if you can identify the exact tap model, obtain the correct part and follow the manufacturer’s instructions safely. Turn off the water first. Otherwise, use a qualified plumber.
Conclusion
A bathroom tap that drips may need a new cartridge or seal, but first identify whether the water comes from the spout, handle, base or connections beneath the basin. The tap’s design determines the repair part. Shut off the supply before inspection, avoid forcing handles or fittings, and use model-specific instructions. If the source is unclear or water is escaping under the basin, have a plumber diagnose it.
For more planning help, read our guide to choosing bathroom taps, review the overhead shower versus hand shower comparison, or see the site’s sanitary products. For examples of brand-specific leak troubleshooting, consult Delta’s two-handle faucet guidance and Moen’s faucet leak FAQ.