Why will my basin pop-up plug not hold water?

How a pop-up waste linkage works, the adjustment that fixes most of them, and what to do when the seal itself has gone.

Difficulty: beginner
Time: 30 min
Read: 3 min

Short answer

Almost every pop-up that will not seal is a linkage adjustment. There is a screw or clip under the basin connecting the lift rod to the plug; slackening it and repositioning the rod lets the plug drop further. If the plug seats fully and still leaks, the seal on its underside has perished.

A pop-up waste is a plug on a stem, lifted by a horizontal pivot rod that passes through the waste body and is linked to the lever behind the tap. Everything about how well it seals comes down to how far that plug can drop.

What you'll need

A torch
A screwdriver or pliers
A replacement plug seal if needed
A bowl and cloth

Step by step

Test how it fails.Fill the basin and watch. A slow drop over minutes means the plug seal. Water disappearing quickly means the plug is not seating at all.
Look under the basin with a torch.Find the horizontal pivot rod entering the back of the waste body, the vertical lift rod behind the tap, and the flat strap with holes that connects the two.
Operate the lever and watch the linkage.You should see the pivot rod rise and fall. If the plug barely moves, the linkage is fouling or the strap is on the wrong hole.
Slacken the clip and let the plug settle.Undo the small screw or clip holding the pivot rod to the strap. With it free, the plug should drop fully into its seat under its own weight.
Retighten with the plug fully down.Hold the plug seated, take up the slack in the linkage, and tighten the clip. That sets the closed position where it needs to be.
Move the strap a hole if the travel is wrong.If the plug now closes but will not lift enough to drain freely, move the pivot rod to a different hole in the strap and readjust.
Check the pivot rod seal.The pivot rod passes through the waste body on a rubber ball seal held by a nut. If it drips there, tighten the nut gently or replace the seal.
Inspect the plug seal itself.Lift the plug right out — most twist and pull free. There is a rubber ring or gasket on the underside. Hardened, split or missing means it will never hold.
Clean the seat before refitting.Hair, soap and toothpaste build a ridge on the seat that holds the plug open by a fraction of a millimetre, which is enough.
Consider a click-clack replacement.If the linkage is corroded or parts are unavailable, a push-button click-clack waste replaces the whole thing with no linkage at all, and fits the same hole.

Tips

Adjust with the plug held fully down. Setting the linkage with the plug halfway is the reason most adjustments do not work.
Clean the seat and the plug underside every few months — the build-up there causes more slow leaks than worn seals do.
Click-clack wastes have no linkage to go out of adjustment, which is why they have largely replaced pop-ups.

Common mistakes

Overtightening the pivot rod nut to stop a drip — The nut compresses a rubber ball seal. Overtightened, it grips the rod so the plug will not move freely, and it deforms the seal so it leaks anyway.
Assuming a leaking plug means a new waste — The overwhelming majority are a slack linkage or a dirty seat. Both are free to fix and take ten minutes.

If it doesn't work

Water drains away in a few seconds

Cause: Plug not seating — linkage too short — Fix: Slacken the clip, seat the plug fully, retighten.

Slow drop over several minutes

Cause: Perished or dirty plug seal — Fix: Lift the plug, clean the seat, replace the rubber seal.

Plug will not lift enough to drain

Cause: Linkage on the wrong hole or over-adjusted — Fix: Move the pivot rod one hole and readjust.

Drip from the back of the waste under the basin

Cause: Pivot rod ball seal — Fix: Nip the nut up gently; replace the seal if it persists.

Questions people ask

Can I remove the pop-up mechanism altogether?

Yes — pulling the pivot rod out and using a rubber plug works, though you must plug the hole the rod came through or it will leak. A click-clack waste is a tidier permanent answer.

Why does my basin drain slowly as well?

The same plug stem collects hair and soap into a solid clump. Lift the plug right out and clean it; it is the commonest cause of a slow basin.