Domakihub How to Fit a Bottle Trap Under Any Basin or Sink
Replace or install a bottle trap in under 30 minutes with basic tools and no special plumbing licence.
Reviewed by Domakihub home & decor pros · 2026-06-23 · 5 min read
A bottle trap is the compact, cylindrical alternative to a P-trap that sits directly beneath a basin waste — common in Greek bathrooms, holiday apartments, and hotel en-suites where cabinet space is tight. The video above walks through a real installation; this guide adds the preparation steps, Greek-context sizing notes, and the checks that prevent a call-back leak. Whether you are refreshing a rental villa bathroom or replacing a cracked trap in an Athens apartment, the job takes under half an hour and requires no licensed plumber in Greece under current regulations — as long as you are connecting to an existing waste pipe and not altering the soil stack.
What a Bottle Trap Does and When to Replace It
A bottle trap creates the water seal (usually 50 mm depth) that blocks sewer gases from rising through the waste pipe into the room. The bulb-shaped chamber retains a small volume of water even when the basin is drained. Over time — especially in hard-water areas like the Aegean islands — lime scale builds up inside the chamber, reducing flow and causing slow drainage. UV exposure in bathrooms with strong sunlight can also embrittle the plastic body, leading to hairline cracks.
You should replace a bottle trap if you notice persistent slow drainage that does not clear with a drain unblocker, visible cracks or weeping around the body, a sulphur smell that persists after cleaning, or if you are fitting a new basin and the old trap is more than ten years old. Chrome-plated brass traps are available for exposed under-sink areas in hotels and show bathrooms; white or chrome plastic traps suit concealed installations.
Sizing, Tools, and Materials
Greek basin wastes are almost universally 32 mm (1¼ inch) in outlet diameter, matching the European standard. Kitchen sinks use 40 mm (1½ inch). Confirm your size before purchasing — hold a tape to the threaded outlet of the waste fitting under the basin. Telescopic bottle traps have an adjustable outlet arm, which is worth the small extra cost when your wall pipe entry is not at a standard height.
You will need: an adjustable wrench or slip-joint pliers, a small bucket and old towel, plumber's PTFE tape, and the new bottle trap kit (trap body, compression nut, outlet pipe, and wall connector). PTFE tape is optional if the new trap has pre-fitted rubber washers — do not add both or you risk over-compression.
How to Fit a Bottle Trap: Step by Step
- 1
Turn Off the Water and Clear the Cabinet
You do not need to isolate the water supply to replace a bottle trap — it connects only to the drain, not the supply. However, place a small bucket directly under the existing trap before you loosen anything. Old traps retain the water in their seal, and you will get a slow pour of stale water the moment the body breaks free. Remove everything from the under-sink cabinet so you have full arm room.
- 2
Remove the Old Trap
Unscrew the large hand-tight ring nut that connects the trap body to the basin waste outlet — most are plastic and turn counter-clockwise by hand; if they are seized, use slip-joint pliers with a cloth to protect the surface. Then loosen the compression nut where the trap outlet arm enters the wall or floor pipe socket. Pull the old trap away and empty it into your bucket. Use a cloth to clean around the waste outlet thread and the wall pipe socket — any old limescale or sealant will prevent a clean seal on the new fitting.
- 3
Assemble the New Trap Dry First
Before applying any tape, thread all the components together loosely by hand to confirm alignment. Fit the slip nut and rubber washer onto the inlet (the wide top of the bottle body) and thread it onto the basin waste outlet. Extend the outlet arm to reach the wall socket — on a telescopic model, slide the arm to the correct length. Check that the outlet arm slopes very slightly downward toward the wall (a few millimetres is enough; a steep drop is not needed and wastes the water seal depth). Mark the arm with a pencil if you need to trim it with a hacksaw.
- 4
Seal and Tighten All Joints
Wrap two to three turns of PTFE tape clockwise around any threaded male connections that do not have a pre-fitted rubber washer — typically the wall-socket fitting. Rubber washers on the slip nuts at the inlet and outlet arm do not need tape; tighten these firmly by hand and then a further quarter-turn with pliers. Do not overtighten plastic nuts: snug plus a quarter-turn is enough; forcing further will crack the nut or distort the washer and cause leaks. Ensure the bottle body hangs vertically — if it tilts, the seal depth on one side will be reduced.
- 5
Test for Leaks
Run the cold tap steadily for 30 seconds, then the hot for 30 seconds. Watch every joint: the inlet nut at the top of the bottle, the body seam if the trap has a removable base, and the outlet compression at the wall. Dry all surfaces with tissue paper first so a slow weep is immediately visible. If a joint seeps, tighten it by an additional eighth-turn and retest. Fill the basin fully and release the waste plug in one go to stress-test the joints under surge flow. If everything stays dry, the job is done.
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FAQ
- Can I fit a bottle trap myself in Greece, or do I need a licensed plumber?
- Replacing a bottle trap is classified as routine maintenance under Greek building regulations and does not require a licensed plumber (αδειούχος υδραυλικός). You are connecting to an existing waste pipe, not modifying the soil stack, gas pipework, or mains supply. However, if you are fitting a new basin from scratch or the work involves altering the soil stack, a licensed plumber is required and the work must comply with ELOT EN 12056 drainage standards.
- My bottle trap keeps losing its water seal and I smell drains — what is wrong?
- A lost water seal almost always means the trap is drying out (common in holiday homes left empty for weeks), the outlet pipe has an air-admittance valve fault, or the trap depth is too shallow for the pressure fluctuations in the building's soil stack. For holiday rentals or seasonal properties in Greece, pour a capful of olive oil into every waste after closing up — oil floats on the water seal and reduces evaporation significantly. If the smell returns within days of use, the stack may need an air-admittance valve or the trap depth may need upgrading to 75 mm.
- What is the difference between a bottle trap and a P-trap, and which should I choose?
- A P-trap has a horizontal U-bend visible from the side and projects further out from the wall, making it easier to maintain but requiring more cabinet depth. A bottle trap is more compact vertically, making it ideal for pedestal basins and slim vanity units common in Greek apartments and hotel bathrooms. Both provide the same 50 mm water seal when correctly fitted. Choose a P-trap where the cabinet is deep enough and you want the easiest access for cleaning; choose a bottle trap where space is the priority. Both are equally code-compliant for basin drainage in Greece.