Domakihub How to Fix a Leaking Bath Trap (and When to Call a Plumber)
Diagnose and repair the most common bath waste trap leaks before they damage the floor or ceiling below.
Reviewed by Domakihub home & decor pros · 2026-06-23 · 5 min read
A dripping bath trap is one of the most common plumbing calls in Greek homes, holiday rentals, and hotels — and one of the easiest to overlook until water stains appear on the ceiling below. The video above shows the leak being traced and fixed on a real job. This guide walks you through the same process step by step, covering everything from identifying the source to deciding whether a quick reseal will do the job or whether it is time to replace the trap entirely.
What Is a Bath Trap and Why Do They Leak?
The bath trap (also called the bath waste trap or P-trap) is the curved section of pipe directly beneath the bath waste outlet. Its job is to hold a small amount of water at all times, which blocks sewer gases from rising into the room. In most Greek apartments and villas the trap is a 40 mm or 50 mm plastic unit hidden inside a panel or under a shallow wooden frame beneath the bath.
Leaks develop for three main reasons: the rubber washer inside the waste fitting dries out and cracks, the slip-joint nuts connecting the trap arms work loose over time (particularly in older buildings where the floor flexes), or the trap body itself cracks from age, limescale build-up, or someone applying too much torque when clearing a blockage. Hard water — common across much of mainland Greece and the islands — accelerates limescale deposits and shortens the life of plastic components.
Before You Start: Safety and Access
Bath trap repairs do not involve mains electrical work or gas, so the main hazards are moisture damage and working in a confined space. Turn the water supply off at the isolation valve on the hot and cold feeds (or at the main stopcock if there is no isolator), and place an old towel or shallow tray under the trap to catch residual water. Remove the access panel if one is fitted — most modern Greek bathrooms have a removable side panel; older built-in baths may require unscrewing a tiled panel or working through the overflow access hole.
If there is no access panel at all and the bath is fully tiled in without any service opening, do not break tiles yourself. Call a licensed plumber who can advise whether a McAlpine-style top-access trap can be retrofitted through the waste grid alone, avoiding tile removal entirely.
How to Fix a Leaking Bath Trap: Step by Step
- 1
Locate the exact source of the leak
Fill the bath with 10 cm of water and then drain it while watching the trap from the access panel with a torch. Look for drips at three points: the waste outlet flange where it meets the bath base, the slip-joint nut connecting the trap to the waste pipe, and the body of the trap itself. Mark the wet spot with a piece of tape so you do not lose track of it once the water has dripped away.
- 2
Check and tighten any loose slip-joint nuts
Plastic slip-joint nuts (the large ribbed collars on each end of the trap) can often be hand-tightened by half a turn. Do not use a pipe wrench on plastic — you will crack the nut. Use a pair of slip-joint pliers with a rag wrapped around the jaws for grip without damage. Retest by filling and draining the bath again before proceeding further.
- 3
Replace the flat washer in the waste outlet
If the leak is at the flange where the waste grid meets the base of the bath, unscrew the waste grid (usually a flat-head or cross-head slot in the centre of the grid). Lift out the old flat rubber or neoprene washer seated beneath the flange. Bring the old washer to a hardware shop to match the size — standard Greek suppliers stock 40 mm and 50 mm sizes. Fit the new washer dry, apply a thin bead of plumber's silicone around the underside of the flange, then screw the waste grid back down firmly by hand plus a quarter turn.
- 4
Replace the trap if the body is cracked or the joint leaks after retightening
Turn off the water supply and place a bucket under the trap. Unscrew both slip-joint nuts by hand and slide the old trap out. Note the pipe centres and the distance from the waste outlet to the standpipe so you buy a compatible replacement — take a photo before removing. Most Greek builders' merchants carry 32 mm and 40 mm bath P-traps; for tight spaces under a freestanding bath, a compact bottle trap or a 75 mm-seal McAlpine trap is a good choice. Fit the new trap hand-tight first, check alignment, then snug the nuts an additional quarter turn. Do not overtighten plastic.
- 5
Test thoroughly and restore the access panel
Run the bath to full and drain completely while watching the trap for a full drain cycle. Check again 10 minutes later when the pipes have had time to settle. If bone dry, replace the access panel. If you still see a drip at the waste flange even after fitting a new washer, the bath base itself may be cracked around the outlet socket — a repair that requires silicone from above and, in some cases, a new waste fitting bonded from inside the bath.
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FAQ
- Can I use PTFE tape to stop a leaking bath trap joint?
- PTFE tape is designed for threaded metal joints and gives little benefit on plastic slip-joint connections, which rely on a rubber ring seated inside the nut rather than thread engagement. If the leak is at a slip joint, the fix is to replace the rubber ring or the whole trap. PTFE tape can help if the waste outlet has a threaded male connection into a female fitting, but this is rare on bath traps.
- How do I know whether the leak is from the trap or from the bath sealant around the rim?
- The test is simple: fill the bath without running any taps, let it sit for five minutes, then drain it. If the leak only appears during draining, the trap or waste fitting is the source. If you see water tracking down the outside of the bath during filling — especially when someone is sitting in it — the silicone sealant at the wall or floor junction is the culprit, not the trap.
- Is this job suitable for a property owner to do themselves, or should they call a plumber?
- Tightening a slip-joint nut, replacing a flat washer, or swapping a plastic P-trap are all tasks a careful homeowner can handle with basic tools and about an hour of time. Call a licensed plumber if there is no access panel, if the pipework is copper or lead (common in pre-1990 Greek construction), if the leak has been running unseen for a long time and there may be hidden water damage, or if the waste outlet socket in the bath base itself is damaged.