DIY GUIDE · PLUMBING & HEATING · CHECKED OCTOBER 2026
How to replace a basin waste and trap yourself
An afternoon. €30–€95 for a new waste, a trap and a hair catcher.
Old plug fitting out, new one in, new trap below: dry-fit, hand tighten, run water and watch. Leave the supply pipes and the electrics alone.
- Every step, start to finish
- Checked October 2026 — sources at the end
- Honest about when to call a pro
FIRST, THE HONEST ANSWER
Do it yourself, or get a plumber?
Do it yourself if…
- The basin stays where it is and only the plug fitting and the trap below it are being changed
- You can reach the underside of the basin, through a vanity door or behind a pedestal
- The waste pipe from the trap to the wall is plastic and in good condition
- You are happy to work slowly on your knees for an hour with a torch
Get a pro if…
- The basin itself is cracked, loose on the wall, or needs to come off to reach the waste
- The waste pipe into the wall is old metal or lead, or it leaks where it enters the wall
- The basin is a stone or glass vessel with an unusual outlet you cannot match
- Water is coming up through the bath or shower as well, which points to a blockage further down
Safety first
- Wear gloves. An old trap holds hair, soap scum and bacteria; wash your hands and the tools when you finish.
- Never mix drain chemicals, and never open a trap that has drain cleaner in it. If you used a chemical unblocker, flush it through with plenty of water first, and wear eye protection.
- Kneeling and reaching under a basin strains the back. The HSA's manual handling guidance treats awkward posture, stooping and twisting as risk factors in their own right; work in short spells and use a kneeling pad.
- If you move a pedestal, make sure the basin is fixed firmly to the wall on its own first. A basin falling off its brackets breaks and cuts.
- Keep water and tools away from any shaver socket, light or fan in the room, and do not touch them with wet hands.
- Use a plastic scraper on ceramic; a metal blade slipping on a basin cuts hands as easily as it scratches the glaze.
Stop here: Stop here: supply pipes, the drain beyond the wall and the electrics
A waste and trap are yours to change, but the supply pipes to the taps, the drain inside the wall and the soil stack are a plumber's work. In a bathroom the electrics are covered by a stricter rule in Irish law: under the Restricted Electrical Works Regulations, S.I. No. 264 of 2013, any modification, installation or replacement of an electrical installation in a special location such as a bathroom is restricted electrical work, which only a Registered Electrical Contractor may carry out and certify, and the CRU prosecutes unregistered work. If a gas boiler or water heater serves the basin's hot tap, any work on it is for a Registered Gas Installer. How to hire a bathroom plumber →
| MATERIAL | COVERAGE | FOR THIS JOB |
|---|---|---|
| Basin waste | Slotted if the basin has an overflow, unslotted if not; check the clamping range | One |
| Basin trap | Bottle or pedestal, to suit your waste outlet and the pipe to the wall | One |
| Hair catcher | Sits loose in the plug hole | One |
| Low-modulus sanitary silicone | Only if the waste's sheet asks for it under the flange | A little; many wastes fit dry |
Will the new trap meet the wall pipe
Drop needed = height of the waste outlet under the basin − height of the pipe into the wall. If the waste outlet sits 560 mm above the floor and the wall pipe enters at 430 mm, the trap has to drop 130 mm, which an adjustable bottle or pedestal trap covers.
Measure from the floor to the underside of the old waste and to the centre of the pipe into the wall. If the difference is more than the trap's adjustment, a short length of pipe and a bend do the rest.
Look inside the basin under the rim for a small hole or slot. That is the overflow, and it drains through a channel into the waste. A basin with an overflow needs a slotted waste, with openings in its side that let overflow water in. A basin without one needs an unslotted waste, or the overflow on a slotted one leaks straight into the cupboard.
A click-clack waste opens and closes when you press the plug. A pop-up uses a lever behind the tap. A plain waste takes a plug on a chain. The click-clack is the simplest to fit because it has no linkage. If your tap has a pop-up rod, you can still fit a click-clack and leave the rod hole capped.
Every waste has a range of basin thickness it can clamp. One maker's sheet we read gives 23 to 45 mm without a spacer, with a spacer supplied for thinner basins. Measure the thickness of the basin at the waste hole before you buy, especially on a thin vessel basin.
A bottle trap is compact and suits a vanity unit or a basin on show. A pedestal trap has a longer, adjustable leg that hides behind a pedestal. Both need to suit the size of your waste outlet, which on a bathroom basin is almost always the smaller of the two common sizes.
Look at where the old trap meets the pipe to the wall. Its outlet height and direction decide what fits. An adjustable-height trap gives you room to match the pipe without cutting it.
THE PART THAT DECIDES THE FINISH
Before you start — the basin and what is under it
Open the vanity or look behind the pedestal with a torch. Match what you see to one of these and do its prep first.
Vanity unit with a bottle trap
The basin sits in or on a cabinet and the trap is inside it.
- Empty the cabinet and lay towels on its floor
- Put a bucket under the trap before you touch a nut
- Check the back of the cabinet for old water stains and swollen board, which show how long it has leaked
- Take a photo of how the trap and pipe sit so you can match the new one
Pedestal basin
A wall-hung basin with a ceramic pedestal hiding the trap.
- Check whether the pedestal is screwed to the floor or simply sits under the basin
- Ease the pedestal forward to get at the trap only if the basin is fixed firmly to the wall on its own
- If the basin drops or rocks when the pedestal moves, stop and support it before you go further
- Lay a towel on the floor for the pedestal so it cannot chip the tiles
Old metal waste sealed with putty
Common in older bathrooms. A brass waste bedded in plumber's putty or old sealant.
- Cut round the flange inside the basin with a utility knife to break the old seal
- Spray penetrating oil on the backnut under the basin and give it time
- Have water pump pliers ready to hold the waste body while you turn the backnut
- Expect old putty in the hole; you will scrape it all off before the new waste goes in
Pop-up waste with a lever behind the tap
A rod behind the tap moves a linkage under the basin.
- Undo the small clamp that joins the rod to the linkage under the basin and lift the rod out
- Note how the linkage sits in the waste before you take it apart
- Decide whether you are fitting a new pop-up or a click-clack
- If you fit a click-clack, buy a cap for the rod hole in the tap
THE JOB
How to replace the waste and trap
Set up and clear the space
15 minEmpty the cabinet or ease the pedestal aside as your card above describes. Lay towels, put a bucket under the trap, and put on gloves. Run no water in the basin from now until the end, and tell everyone in the house.
- Put a strip of tape across the basin so nobody uses it
- Keep a bag for the small parts you take off
- Have the new waste and trap out of their packaging and laid out in order
Mistake to avoid: Starting with the basin still in use. Someone runs the tap halfway through and the water goes straight into the cabinet.
Prepare the basin and the pipe
15 minThis is the prep from the cards above. Break any old sealant round the plug hole with a utility knife. Spray an old metal backnut with penetrating oil. Look at where the trap joins the wall pipe and check that pipe is sound, firm and clean at its end.
- Run a finger round the inside of the wall pipe to feel for a crack
- Mark the old trap's outlet height on the cabinet side with a pencil
- Leave penetrating oil at least ten minutes before you try the nut
Mistake to avoid: Finding out after the old trap is off that the wall pipe is cracked. Look first, and if it is, stop and call a plumber.
Take off the old trap
15 minUnscrew the nut where the trap meets the waste and the nut where it meets the wall pipe, by hand if you can. Lower the trap into the bucket as it comes free and tip the water and sludge out. Look into the wall pipe with a torch: if it is full of hair or soap, clear it now while it is open.
- Hold the trap level as it comes off so it does not slop
- A bent coat hanger or a small brush clears the first part of the wall pipe
- Keep the old seals until the new trap is on, to compare sizes
Mistake to avoid: Using pliers on an old plastic trap nut and crushing it. If it will not turn by hand, a gentle grip with a cloth round the nut is enough.
Remove the old waste
20 minUnder the basin, undo the backnut that holds the waste body. On an old metal waste, hold the waste from above with pliers wrapped in a cloth while you turn the nut below. Once the nut is off, push the waste up and out from the plug hole. Scrape every trace of old putty and sealant from the hole and the basin round it, then wipe it clean and dry.
- A plastic scraper will not scratch a ceramic basin; a metal one will
- Clean the underside round the hole too, where the new seal will bear
- Check the hole edge for chips that could stop a seal bedding
Mistake to avoid: Leaving old putty in the hole. The new seal sits on a ridge of hard putty and the waste leaks from day one.
Fit the new waste
20 minFollow the order on the waste's own sheet. Typically a seal goes under the flange inside the basin, the waste drops through the hole, and below the basin a second seal, a spacer if needed and the backnut go on. On a slotted waste, line the slots up with the overflow channel. The maker we read asks for no more than hand tight plus a quarter turn on its plastic ferrule and calls it a dry fix, with no sealant.
- Check the flange is centred in the hole before the nut bites
- Turn the waste so its outlet points at the wall pipe before the final quarter turn
- Use the spacer for a thin basin, as the sheet's thickness range explains
Mistake to avoid: Overtightening the plastic nut to stop a leak. It cracks or distorts the seal; a leak at a waste means a seal out of place, not a loose nut.
Fit the new trap
15 minSlide the trap's inlet nut and seal onto the waste outlet, then push the trap up and run the nut on by hand. At the other end, slide the outlet nut and seal onto the wall pipe and push it into the trap's outlet. Adjust the trap's height so it meets both without strain, then hand tighten both nuts and give each the small extra turn the trap's sheet allows.
- Make sure each seal sits square in its nut before you tighten
- The trap should hang naturally; if you have to pull it to reach, adjust it or add a bend
- Hand tight is usually enough on plastic trap nuts
Mistake to avoid: Forcing a trap to reach a pipe at the wrong height. The strain pulls the seals out of line and they weep a little at every use.
Fit the click-clack or linkage
10 minPush the plug into the waste, or fit the pop-up linkage as its sheet shows. Press the plug several times to check it opens fully and seals when closed. On a pop-up, adjust the linkage until the plug lifts cleanly when the rod goes up.
- A click-clack should close with a firm press and open with another
- Fit the hair catcher now if the plug lifts out
- Cap the old pop-up rod hole if you no longer need it
Mistake to avoid: Leaving a pop-up linkage loose. The plug drops half shut over time and the basin starts draining slowly again.
Test with a full basin
20 minClose the plug and fill the basin until water runs into the overflow. Watch under the basin with the torch while it fills: the waste flange, the backnut and the overflow slot. Then open the plug and let the full basin drain at once. Watch both trap nuts as the water rushes through, and run a dry tissue round each joint.
- A full basin draining is the hardest test the joints will face
- Repeat the fill and drain twice
- Leave dry kitchen paper on the cabinet floor overnight
Mistake to avoid: Testing with a trickle from the tap. Small flows hide leaks that a full basin draining at once will show.
Finish and tidy
15 minIf the waste sheet asks for a bead of sanitary silicone round the flange, apply it now and leave it to cure before use. Refit the pedestal, put the cabinet back in order and leave its door open for a few hours so the board dries out.
- Smooth any silicone with a wet finger in one pass
- Clean the old trap and waste before you bin them
- Note the date, so you know when the trap was last cleaned
Mistake to avoid: Packing the cabinet straight back. A small weep you missed shows up as a damp box of spare toiletries a week later.
The mistakes that show
- Buying an unslotted waste for a basin with an overflow
- Leaving old putty or sealant in the waste hole
- Overtightening plastic nuts until they crack
- Forcing a trap to meet a wall pipe at the wrong height
- Testing with a dribble instead of a full basin
Stop here and get a plumber
- The basin is cracked, loose on its fixings, or has to come off the wall
- The waste pipe into the wall is cracked, metal, or leaks at the wall
- The basin's taps or their supply pipes need to be changed or moved
- The blockage is further down the drain and other fittings are backing up too
| WHAT YOU SEE | WHY, AND THE FIX |
|---|---|
| Water in the cabinet when the overflow is used | An unslotted waste on a basin with an overflow, or the slots not lined up with the overflow channel. Fit a slotted waste or turn it so the slots face the channel. |
| Leak round the plug hole underneath | The seal under the flange is not bedded, or old putty is still in the hole. Take the waste out, clean the hole fully and refit. |
| Drip from a trap nut | The seal inside the nut is twisted or missing. Undo it, seat the seal square and hand tighten again; replace a crushed seal. |
| Basin still drains slowly | The blockage is in the wall pipe, not the trap. Open the trap and clear the pipe beyond it. |
| Gurgling and a smell after draining | The trap is being siphoned and loses its water. Make sure the trap is a proper depth seal type; if it keeps happening, the venting needs a plumber. |
| Click-clack will not stay closed | The plug's spring mechanism is fouled with hair or the plug is not pushed fully in. Pull it out, clean it and push it home. |
| Trap will not reach the wall pipe | The new trap's outlet is at a different height or angle. Use an adjustable trap, or add a short pipe and bend. |
| Waste spins when you tighten the nut | The seal below is too slippery or the basin is thinner than the waste's range. Hold the waste from above and fit the spacer if one is supplied. |
WHAT YOU SAVE
What it costs to do it yourself
| Basin waste, click-clack or plug and chain | €15.29–€19.59 |
|---|---|
| Bottle or pedestal trap | €14.99–€17.99 |
| Hair catcher | €4.99 |
| Chrome bottle trap, if the trap is on show | €76 |
| Total | €30–€95 |
| DIY total | €30–€95 |
Guide prices compiled by the Locufy team from published Irish and UK provider price lists and 2026/27 cost guides. Updated 2026.
The low figure is a plastic trap and a simple waste; the high one is a chrome trap for a basin where the pipework is on show. Either way, it costs a fraction of a call-out.
RATHER NOT?
Bathroom plumbers near you, with prices shown
The ones who cover your area, nearest first, with one score from every review. No account needed to look.
Or post the job free and let them come to you.
Every few months, put a bucket under the trap, undo it, rinse it and refit it. Five minutes now saves a slow basin later.
Empty the hair catcher into the bin rather than rinsing it down the basin. Hair and soap together are what block a bathroom waste.
An old brass waste is metal and goes in the metal skip at your local civic amenity site; mywaste.ie shows what your nearest recycling centre accepts. A small old plastic trap can go in your general waste bin once it is rinsed.
If you ran a bead of silicone round the flange, keep the basin dry for the time the tube says before you use it.
Replacing a basin waste and trap: questions people ask
Yes. A basin waste and trap are push and screw fittings with rubber seals, and changing them is a householder job. Moving the basin or changing its supply pipes is a plumber's job.
Look for an overflow hole or slot under the basin rim. If there is one, fit a slotted waste with the slots lined up to the overflow channel. If not, fit an unslotted waste.
Many modern wastes fit dry on their own seals. The one we read is a dry fix with no sealant. Follow your waste's own sheet; some ask for a bead under the flange.
Hand tight, plus a small extra turn at most. One maker sets the limit at hand tight plus a quarter turn. Overtightening cracks plastic nuts.
The trap may be losing its water seal through siphoning, or the old pipe beyond it is fouled. Clean the pipe; if the smell persists, a plumber should check the venting.
Locufy's Irish price guide puts bathroom plumbing at €300–€1,500 per job, typically €700. A waste and trap swap on its own sits well below that.
MORE GUIDES
More DIY guides
Sources — checked October 2026
- McAlpine — centre-pin basin waste and P-trap installation and maintenance instructions
- HSA — guide to the manual handling of loads (General Application Regulations 2007)
- S.I. No. 264 of 2013 — Electricity Regulation Act 1999 (Restricted Electrical Works) Regulations
- CRU — RGI and Safe Electric schemes
- MyWaste.ie — DIY equipment: metal and timber at civic amenity sites
- MyWaste.ie — DIY waste, including old sanitary ware
- Woodie's — waste plugs and chains, basin wastes, hair traps (price check)
- Woodie's — waste pipe fittings and traps (price check)
- DIY.ie — wastes and traps (price check)