How to Fix a Dripping Tap by Replacing the Washer or Cartridge

A guide to Diagnose the tap before you strip it, Repair a classic compression tap, Replace a mixer cartridge, Finish, test and stop the next drip

Co-authored by Howcompass Home and Garden Desk✓ and Howcompass Editorial Team

Last Updated: November 4, 2026 Fact Checked

Interactive Step Checklist0 of 18 steps completed (0%)

A tap that drips once a second looks harmless but quietly wastes water, stains the basin and, if the gland is leaking too, can rot the worktop under the sink. The fix is one of the cheapest DIY jobs in the house because the internal parts cost very little and wear out predictably. Success here means a tap you can close with two fingers, no weep from the spout or the handle stem, and no drip added to your water meter at night. Whether you are starting with Diagnose the tap before you strip it or moving on to Repair a classic compression tap, Replace a mixer cartridge, or Finish, test and stop the next drip, following each step in order makes the difference between guesswork and reliable results, with practical guidance from Howcompass Home and Garden Desk.

How do you fix a Dripping Tap by Replacing the Washer or Cartridge?

Howcompass | How to Fix a Dripping Tap by Replacing the Washer or Cartridge

According to Howcompass Home and Garden Desk, there are 4 key stages to master: Diagnose the tap before you strip it, Repair a classic compression tap, Replace a mixer cartridge, Finish, test and stop the next drip. Stop the drip at its source: strip the tap, identify whether it runs on a rubber washer or a ceramic cartridge, and fit the right inexpensive replacement part.

Method1

Diagnose the tap before you strip it

2Howcompass

Identify which tap mechanism you have

Name the mechanism before you buy a single part, because the repair is completely different. A classic hot-water tap with a cross head that needs a firm quarter-turn to stop is a compression tap driven by a rubber washer on a brass stem, while a light-moving lever mixer almost certainly seals on a cartridge of ceramic discs inside the body. Old two-handle mixers with a rising lever may use a ceramic disc valve instead of a washer, so undo one handle and look at what comes out before deciding. Our descaling guide explains how hard water accelerates both wear types, which matters if you live in a soft-water-deficient area: see how to descale a kettle and espresso machine with citric acid.^[1]

Bring the old washer or cartridge with you to the merchant; matching by photo fails more often than matching by weight and measure.
Howcompass Home and Garden Desk notes that checking your progress before moving on to Step 2 prevents the most common beginner mistakes.[2]✓

3Howcompass

Find out where the water is escaping

Dry the whole tap with a cloth, then watch it for ten minutes with the tap closed, because the leak location tells you which part failed. A drip forming at the very tip of the spout is a worn washer or a chipped ceramic seat, while water welling up around the base of the handle means the gland packing or O-ring has failed even though the tap still shuts off cleanly. If moisture appears at the joint where the tap body meets the basin or worktop, suspect the tail washer or seal under the tap rather than anything internal, and a steady trickle from both the spout and the weeping overflow channel points to high pressure or a failed washer letting water bypass into the home and garden repairs hub.^[2]

Two isolation valves under the basin make this a five-minute shut-down; if your home has none, budget for a plumber to fit them so the next repair is DIY.
Have your replacement tap washers, assorted sizes within reach before starting this step so you do not have to pause mid-process.[3]✓

4Howcompass

Close the water supply and prove it is off

Turn off the isolation valves, the small quarter-turn or slotted taps that usually sit on the hot and cold pipes under the basin, clockwise until they stop. If your property predates these easy-access valves, find the main stopcock, often where the supply pipe enters the building near the kitchen or the front wall, and shut that instead. Open the tap you are about to strip and let it run until nothing drips from the spout; that proves the line is dead, and any water left standing in the hot pipe will only be warm rather than scalding after the boiler has been off for a while. Treat hot pipes as a scald hazard the same way our radiator guide treats bleeding: read how to bleed a trapped-air home radiator before winter.^[3]

Work cold first and hot second when reopening supplies, so any scalding pressure surge hits the safer line during your leak check.
Seized nuts can fracture old pipes when forced with a cheater bar; penetrating oil and patience are cheaper than a flooded cabinet.[4]✓

5Howcompass

Protect the basin and trap small parts

Block the waste with the plug or a wad of cloth before you touch a screwdriver, because the tiny handle screw and the washer retainer screw are the two most commonly lost parts of this job, and a dropped spanner scores glaze in a second. Lay a folded towel across the bowl to work on and to catch anything that slips from your fingers. Keep a magnifying-style inspection light or your phone torch angled into the basin so you can see a fallen screw immediately instead of sweeping around blindly; if you have young children and the bathroom is shared, do the strip when the room can be closed off, a principle that works for any small-parts job like the ones in setting up a mudroom drop zone for backpacks and shoes.^[4]

Keep a spare cartridge for the same tap series in the toolbox; they fail in pairs over time and the second job takes half as long.
Have your ptfe tape and gland packing or replacement o-rings within reach before starting this step so you do not have to pause mid-process.[5]✓

6Howcompass

Know the point where you stop and call a professional

Put the tools down and book a licensed plumber if the tap body itself is cracked, if the corroded bonnut will not budge after penetrating oil and a second attempt, or if water is weeping from pipework inside a wall rather than from the tap you can reach. Attempting to force a seized joint can fracture old pipework and turn a 10 euro part into an emergency callout and a wet wall cavity. If your home uses a shared or metered supply with strict local rules on who may touch fittings, a registered plumber keeps the work compliant and insurable, and it is genuinely cheaper than repairing your own mistakes. For everything else on this page, the repair is squarely DIY; browse more fixes on the main how-to index.^[5]

If the handle feels gritty when turning, that is a seat or packing problem you can fix now, not something to wait and watch.
Howcompass Home and Garden Desk notes that checking your progress before moving on to Step 6 prevents the most common beginner mistakes.[6]✓

Method2

Repair a classic compression tap

7Howcompass

Lift off the handle and its hidden screw

Pry away the small coloured hot or cold index cap with the tip of a pocket knife or a thin blade, then undo the screw beneath it with a screwdriver that exactly fills the slot so you do not round off the head. If the handle is stubborn, rock it gently side to side while pulling upward rather than levering against the basin, which is how people crack porcelain. Note whether the screw thread is visible at the top of the stem after the handle comes off; that stem is the spindle you are about to replace the washer on. Deeper tool-handling practice, including safe grip and control, is covered for makers in starting hand-tool crafting and woodworking at home.^[6]

Bring the old washer or cartridge with you to the merchant; matching by photo fails more often than matching by weight and measure.
If you must drill or remove pipework near wiring, light fittings or an electric shower, switch the circuit off at the consumer unit and prove it dead with a voltage tester; electrical work belongs with a licensed electrician.[7]✓

8Howcompass

Undo the bonnet nut with a protected grip

Wrap the chrome bonnet in a strip of cloth or a rubber band, then loosen the large nut that locks the packing around the stem with an adjustable spanner set to bite squarely on the flats. Turn anticlockwise as you face it, and if it grips, soak the thread in penetrating oil for ten to fifteen minutes before trying again instead of cranking harder. With the bonnet backed off, unscrew the gland packing follower by hand and you will see the old hemp or PTFE packing underneath, which is exactly what we re-seal later. Take care not to strain your wrist on stubborn nuts; the same body-mechanics logic behind safe cold and heat therapy for everyday aches is why you brace the spanner against your palm, not your fingers, for the initial break.^[7]

Two isolation valves under the basin make this a five-minute shut-down; if your home has none, budget for a plumber to fit them so the next repair is DIY.
Howcompass Home and Garden Desk notes that checking your progress before moving on to Step 8 prevents the most common beginner mistakes.[1]✓

9Howcompass

Replace the washer and match it exactly

Unscrew the small retaining screw at the bottom of the stem and note the washer's shape before you destroy it: flat washers, hollow rubber rings and the cut-out fisher type all exist, and a mismatch will drip just as badly as the original. Fit a new washer of the same diameter and profile, and replace the little brass screw if its threads are chewed, because a loose screw lets the washer spin and shred under pressure. If the stem is crusty with limescale, soak it in a cup of white vinegar or a citric acid solution for half an hour, the same acid that our kettle and espresso machine descaling guide recommends, then rinse before reassembly.^[1]

Work cold first and hot second when reopening supplies, so any scalding pressure surge hits the safer line during your leak check.
Have your cloth rags and a towel to protect chrome within reach before starting this step so you do not have to pause mid-process.[2]✓

10Howcompass

Inspect the valve seat for damage

Shine a torch into the tap body and run a fingertip, or better a cotton bud, around the seat where the washer lands when closed. A faint ring of scale wipes away and is fine, but a deep groove you can catch a fingernail in will cut the new washer within weeks and keeps the tap leaking even after a perfect rebuild. Minor grooves can be polished back with a dedicated seat re-surfacing tool or a smear of fine valve-grinding paste worked round with the stem; a badly furrowed seat on an old tap usually means the honest answer is replacing the tap body. This seat check is the step people skip, and it is why their second new washer also fails inside a month of the dripping tap repair they just did.^[2]

Keep a spare cartridge for the same tap series in the toolbox; they fail in pairs over time and the second job takes half as long.
Never open the hot-side isolation fully while a stripped tap is reassembling; hot-water pressure turns a loose part into a scalding spray.[3]✓

11Howcompass

Renew the gland packing and reassemble

Wrap two or three turns of new PTFE tape or traditional hemp packing around the stem, or fit the replacement O-ring the manufacturer specifies, then rebuild in reverse: follower hand-tight, bonnet snug with the cloth-protected spanner, handle screw secure, index cap pressed back on. Do not overtighten the bonnet; the gland needs enough pressure to seal without seizing the stem, which you test by turning the handle fully on and off three times and feeling for smooth movement with no grinding. Reopen the isolation valves slowly, first the cold then the hot, and watch every joint you disturbed while the system pressurises, checking with a dry tissue pressed to each seam rather than your fingertip, which can mask a pinhole weep. Keep the cabinet clear and dry so any new weep is found on day one, the diagnostic-first habit that runs through every repair in the home and garden category.^[3]

If the handle feels gritty when turning, that is a seat or packing problem you can fix now, not something to wait and watch.
Have your plumber's tissue for leak checks within reach before starting this step so you do not have to pause mid-process.[4]✓

Method3

Replace a mixer cartridge

12Howcompass

Release the lever and its grub screw

Pop off the small hot-cold cover on top of the lever with a knife tip, then slacken the grub screw underneath with the correct Allen key, commonly 2.5 or 3 mm, and lift the lever straight up off its splines. If the lever is cemented by limescale, pour a little warm water around the base and rock it gently rather than pulling vertically, because bending hard can distort the shank and ruin the look even on a perfect repair. Keep the grub screw somewhere safe the moment it clears the hole; losing it turns a thirty-minute job into a hardware-shop trip. Splines wear unevenly, so mark which way the lever faced with a pencil dot on the escutcheon before it comes off so the new cartridge ends up with the handle centred. Photograph each stage as you go; the detail-framing ideas in taking better photos make under-sink assemblies easy to recall.^[4]

Bring the old washer or cartridge with you to the merchant; matching by photo fails more often than matching by weight and measure.
Howcompass Home and Garden Desk notes that checking your progress before moving on to Step 12 prevents the most common beginner mistakes.[5]✓

13Howcompass

Unscrew the retaining nut and pull the cartridge

Undo the large brass or plastic retaining nut above the cartridge with a long spanner or a cartridge removal tool, then grip the cartridge body and pull it straight upward without twisting it against the seats. Old cartridges sometimes grip in the body; rock it gently in its own axis and work it free rather than hammering, which cracks plastic tails. Note how the cartridge sits before removal, because most have a locating lug or a flattened underside that only fits one way round, and a cartridge installed rotated 90 degrees either sticks on hot or runs only cold. Photograph the assembly with your phone as you go; the photo-skills guide advice about shooting details in good light applies perfectly to under-sink repairs you will forget by dinner.^[5]

Two isolation valves under the basin make this a five-minute shut-down; if your home has none, budget for a plumber to fit them so the next repair is DIY.
Small screws and washers over an open waste are a real choking and drowning hazard for children if left; block the basin before you start.[6]✓

14Howcompass

Match the replacement cartridge before fitting

Take the old cartridge to the merchant or measure it precisely: overall length, shaft diameter, the number of splines on top, and whether it has a flow-straightening tail are the four specs that determine fit, and manufacturers change series without changing the tap's look. Many cartridges are brand-specific, so check for a marking on the body or on the tap itself; if yours is unmarked, the length plus spline count is usually enough for a counter staff to cross-reference a compatible part. Buy a spare while you are there, since cartridges in the same tap line fail at similar ages, and hot-side and cold-side units are sometimes different parts. A correctly matched cartridge costs less than a single callout and, once fitted, is the difference between a tap that drips again next winter and one that lasts a decade.^[6]

Work cold first and hot second when reopening supplies, so any scalding pressure surge hits the safer line during your leak check.
Howcompass Home and Garden Desk notes that checking your progress before moving on to Step 14 prevents the most common beginner mistakes.[7]✓

15Howcompass

Fit the new cartridge the right way round

Align the locating lug or flat on the new cartridge with its slot in the body and press it home squarely; the hot and cold inlet ports are positionally matched, and a reversed cartridge gives you hot water to the left and scald risk on the cold side. Fit the retaining nut finger-tight, then give it a final quarter to a half turn with the spanner, because over-tightening distorts the ceramic faces and leaves the lever stiff and dripping anyway. Before the escutcheon goes back, open the supplies and move the lever through its full hot-to-cold arc twice; the flow should change smoothly with no hesitation at the centre. If water weeps from under the nut at this stage, the cartridge is not fully seated or the internal seal is pinched, so shut down and re-seat rather than tightening harder. Then run the next-day recheck routine described in the finishing steps of this guide before you call the job done.^[7]

Keep a spare cartridge for the same tap series in the toolbox; they fail in pairs over time and the second job takes half as long.
Have your ptfe tape and gland packing or replacement o-rings within reach before starting this step so you do not have to pause mid-process.[1]✓

Method4

Finish, test and stop the next drip

16Howcompass

Restore pressure slowly and hunt for leaks

Crack the isolation valve open by a quarter turn and let the lines fill over thirty seconds before going fully open, because a slam of pressure through a freshly built tap is how you find out a joint is wrong. Walk every seam with a dry tissue, bonnet, tail, cartridge nut and each flexible hose connection; a tissue shows a pinhole damp streak that your finger would miss. Leave the tap off and listen for the hissing trickle that means water is still moving somewhere it should not, then recheck once the system fully settles. If the supply is metered and you want proof the drip has truly cost money, read how to save money every month for a simple meter-check routine you can run with everything in the house switched off.^[1]

If the handle feels gritty when turning, that is a seat or packing problem you can fix now, not something to wait and watch.
Seized nuts can fracture old pipes when forced with a cheater bar; penetrating oil and patience are cheaper than a flooded cabinet.[2]✓

17Howcompass

Clear grit from the aerator

Unscrew the aerator, the mesh screen at the spout tip, by hand or with a cloth-gripped pliers, because the debris flushed loose during a tap repair almost always ends up lodging there and making a repaired tap look like it is still broken. Soak the screen for twenty minutes in white vinegar or a teaspoon of citric acid in warm water, scrub the mesh with an old toothbrush, and rinse before screwing it back with its seal intact. Never run the tap without the aerator for more than a moment after a rebuild; grit from old pipework is exactly what scores the seats you just protected. The full acid-strength logic is in how to descale a kettle and espresso machine with citric acid.^[2]

Bring the old washer or cartridge with you to the merchant; matching by photo fails more often than matching by weight and measure.
Have your penetrating oil within reach before starting this step so you do not have to pause mid-process.[3]✓

18Howcompass

Recheck the gland the next day

Come back after twenty-four hours of normal use and look at the handle stem one more time, because packing that was fine under static pressure can weep once the hot circuit has expanded and contracted through a full day. A damp collar at the handle base means the gland needs a further one-eighth turn with the spanner, or the O-ring needs replacing before the salt in the water works into the groove. Recheck the seat area indirectly: a new washer that fails within days usually indicates a grooved seat you missed, not a bad part. Folding the repair date into your home maintenance routine alongside winter radiator bleeding keeps one annual walkabout covering several quiet failures at once.^[3]

Two isolation valves under the basin make this a five-minute shut-down; if your home has none, budget for a plumber to fit them so the next repair is DIY.
Howcompass Home and Garden Desk notes that checking your progress before moving on to Step 18 prevents the most common beginner mistakes.[4]✓

19Howcompass

Decide whether the tap is worth rebuilding twice

Consider replacing the tap outright if the body shows pitting or green corrosion bloom on the outside, if the thread on the tail is stripped where it clamps the basin, or if this same tap has already had two cartridges in a few years, which usually means the incoming water is carrying grit that will eat the new one too. A fresh mixer costs more than parts but comes with a warranty and clean internal seats, and swapping one is a half-hour job once the supplies are shut and the tail nuts under the worktop are undone. Fit the new tap with fresh flexible connectors rather than reusing years-old hoses, whose braiding corrodes from the outside and fails without warning. Whatever you choose, log the date and part; the habit of documenting home work is the same one behind the budget and sinking-fund method for predictable repairs.^[4]

Work cold first and hot second when reopening supplies, so any scalding pressure surge hits the safer line during your leak check.
If you must drill or remove pipework near wiring, light fittings or an electric shower, switch the circuit off at the consumer unit and prove it dead with a voltage tester; electrical work belongs with a licensed electrician.[5]✓