Why Is My Tap Leaking? Common Causes

That steady drip in the kitchen or bathroom usually starts as a small annoyance. Then it keeps you awake, stains the basin, and leaves you wondering, why is my tap leaking if I turned it off properly? In most cases, a leaking tap comes down to wear inside the fitting, but the exact cause depends on the type of tap, the age of the plumbing, and how long the problem has been going on.

A leaking tap is easy to put in the too-hard basket, especially if it still seems to work. The trouble is that a minor leak can turn into wasted water, higher bills, damaged tapware, and hidden wear elsewhere in the system. If the leak is linked to water pressure, corrosion, or a faulty valve, the issue may be bigger than the tap itself.

Why is my tap leaking when it's turned off?

If water keeps dripping after the tap is fully off, the internal seal is usually no longer doing its job. In older style taps, that often means a worn washer. In mixer taps, it is more likely a damaged ceramic cartridge. Both parts are designed to stop water flow cleanly, but over time they wear down through regular use, mineral build-up, and pressure changes.

Sometimes the leak is slow and consistent, one drip every few seconds. Other times it starts after the tap handle is tightened harder than usual. That can be a clue that the internal parts are worn rather than simply loose. Forcing the handle tighter rarely fixes the problem for long and can make the damage worse.

The location of the leak matters too. A drip from the spout points to one set of causes, while water around the base of the tap, under the sink, or near the wall flange may suggest failed O-rings, loose connections, or cracked components.

The most common causes of a leaking tap

Worn washers

In traditional compression taps, the washer is one of the most common reasons for leaks. This small rubber piece presses against the valve seat to stop water passing through. Over time it hardens, splits, or becomes misshapen. Once that happens, water can slip past even when the tap is off.

Washers are inexpensive, but replacing them properly is not always as simple as it sounds. If the seat is damaged or rough, a new washer may wear out quickly and the leak can return.

Faulty ceramic cartridges

Many modern taps use ceramic disc cartridges instead of washers. These are durable, but not immune to wear. A cracked cartridge, grit caught inside, or internal deterioration can stop the tap from sealing properly. This is especially common where there is sediment in the water or if the tap has been in service for years.

Cartridges need to be matched correctly to the tap model. Using the wrong part or fitting it poorly can leave you with the same leak and a tap that is harder to operate.

Worn O-rings and seals

If the leak appears around the handle or base of the tap rather than from the outlet, worn O-rings are often to blame. These seals prevent water escaping around moving parts. As they age, they can flatten, crack, or shift out of place.

This type of leak may only show when the tap is turned on, or it may leave moisture around the base all the time. Left alone, it can damage benchtops, cabinetry, or the vanity below.

Corroded valve seats or internal parts

Older taps can suffer from corrosion where internal components meet. The valve seat is a common trouble spot. If it becomes pitted or rough, the washer cannot seal against it cleanly. In coastal and regional areas, water quality and environmental conditions can also play a part in how quickly tap components wear.

Corrosion is one of those problems where a quick fix may not hold. If the metal surfaces are already damaged, replacing one small part may only provide short-term relief.

Water pressure issues

Not every leaking tap is caused by a failed tap part. High water pressure can force water through seals that are beginning to weaken. Pressure fluctuations can also shorten the life of tap components over time.

If more than one fixture in the property is acting up, or if you have banging pipes, inconsistent flow, or repeated leaks, it is worth looking at the wider plumbing system rather than only the tap.

Why is my tap leaking at the base or under the sink?

A tap that leaks from the base, spindle, or under the sink can point to a different problem than a dripping spout. In some cases, the body of the tap has loosened over time. In others, the flexible hoses, seals, or threaded connections underneath are the issue.

This can be more serious than it looks. Water under a sink often goes unnoticed until cupboards swell, mould develops, or the flooring starts to lift. If the area under the basin feels damp, smells musty, or shows staining, the leak may have been there longer than expected.

For property managers and commercial operators, these slower leaks can become expensive because the tap itself is only part of the problem. Joinery, cabinetry, and wall linings often wear the cost as well.

Can I fix a leaking tap myself?

Sometimes, yes. If it is a simple issue, such as a loose aerator or a known washer replacement on an older tap, a confident homeowner may be able to manage it. But there is a difference between stopping a drip for now and fixing the underlying problem properly.

Taps vary a lot by brand, age, and design. Some have hidden grub screws, proprietary cartridges, or fittings that can be damaged during removal. It is also easy to scratch finished tapware, over-tighten parts, or reassemble the tap incorrectly. If you shut off the wrong valve, fail to isolate the water completely, or miss a worn internal seat, you can end up with a bigger repair than the one you started with.

The other factor is age. If the tap is older, the leak may be a sign that the fixture is reaching the end of its service life. Replacing one seal in a heavily worn tap may not be the best value if another component fails soon after.

Signs it is time to call a plumber

If the leak keeps coming back, if the tap is hard to turn, or if water is appearing where it should not, it is time to have it checked properly. The same goes for leaks under sinks, inside vanities, behind walls, or around tiled surfaces.

A licenced plumber can work out whether the issue is isolated to the tap or linked to pressure, pipework, or fixture condition. That matters because leaking taps are sometimes symptoms rather than stand-alone faults. On rural properties and older homes, that broader check can save a lot of guesswork.

There is also the practical side. Some taps are worth repairing, while others are better replaced with a more reliable unit. A good plumber will tell you which option makes sense based on the condition of the fitting, availability of parts, and the likely lifespan of the repair.

How to reduce the chance of leaks in future

You cannot stop every tap from wearing out, but you can reduce the likelihood of early failure. Avoid over-tightening handles, as that puts extra strain on washers and seals. If a tap starts to drip occasionally, have it looked at before the leak becomes constant. It is usually cheaper and simpler to repair a tap early than deal with damaged cabinetry or replace the whole fitting later.

It also helps to pay attention to the rest of the plumbing system. Pressure issues, sediment, and ageing pipework can all shorten the life of tapware. If leaks are becoming a pattern across the property, it is worth asking whether the problem sits deeper in the system.

For homes, rentals, farms, and commercial sites across the South West, the best approach is a practical one. Fix small plumbing issues before they become bigger ones, and do not assume a dripping tap is ever just a drip.

If you have been asking why is my tap leaking, the answer is usually straightforward once the right part of the tap is inspected. The important thing is not letting a small fault sit long enough to become water damage, wasted water, or a more involved repair.