Domakihub How to Install a Bathroom Sink: Complete Step-by-Step Guide
From removing the old basin to tightening the last fitting — done right the first time.
Reviewed by Domakihub home & decor pros · 2026-06-23 · 5 min read
Replacing a bathroom sink is one of the most rewarding weekend plumbing jobs you can tackle yourself — no specialist licence required and the payoff is immediate. The video above walks through every plumbing connection in real time; this article distils the same process into clear steps you can follow at your own pace, with notes relevant to homes, holiday rentals, and hotel bathrooms across Greece. Whether you are upgrading a tired basin in an Athenian apartment or refreshing a villa bathroom before the summer rental season, the method is the same.
What You Need Before You Start
Gather all materials before touching the water supply. You will need a new sink (drop-in, undermount, or pedestal — choose to match your vanity cut-out), a faucet if not pre-fitted, a drain assembly, supply lines (flexible braided stainless, 30–40 cm), plumber's putty or silicone sealant, a P-trap kit, and an adjustable wrench plus basin wrench for tight spaces. In Greece, standard sink threads follow metric sizing, so check that supply line connectors are M10 or M8 to match your faucet body.
Also confirm the rough-in dimensions of your existing drain stub-out before buying a new P-trap. Greek apartments built before 2000 often used 40 mm drain pipes; newer builds and EU-standard renovations use 40–50 mm. A reducing adapter costs less than one euro and prevents a wasted trip to the hardware shop.
Water Supply and Drainage Basics in Greece
Greek mains water pressure typically runs between 2.5 and 4 bar, which is well within the tolerance of standard ceramic disc faucets. If your building has a roof tank (very common outside Athens city centre), pressure may be lower — 1–1.5 bar — and this is fine for basin use but worth knowing before diagnosing a 'weak' tap later.
Greek building code requires an accessible shut-off valve under every sink. If your existing pipework has no isolation valve (common in pre-1990 kitchens and bathrooms), fit one now while the supply is already off. Quarter-turn ball valves rated PN16 are widely available at plumbing merchants (υδραυλικά) for under €5 and will save you considerable hassle in future.
How to Install a Bathroom Sink
- 1
Shut Off the Water and Remove the Old Sink
Turn the isolation valves under the sink clockwise until fully closed, then open the tap to release residual pressure. Disconnect the supply lines from both the hot and cold valves, then loosen the P-trap slip nut by hand or with groove-joint pliers and pull the trap free. If the old sink is a drop-in, cut any silicone bead around the rim with a utility knife and lift it straight up. For a pedestal sink, remove the pedestal bolts at the floor and lift the basin off the wall bracket. Have a towel ready — some water will remain in the trap.
- 2
Fit the Faucet and Drain Before Lowering the Sink
It is far easier to install the faucet and drain assembly while the sink is on a workbench or the floor than to do it in situ with your arms crammed under a vanity. Thread the faucet mounting nut from below and hand-tighten, then finish with a basin wrench to snug — do not overtighten ceramic or composite sinks. For the drain, roll a thin rope of plumber's putty and press it under the drain flange lip, then insert the flange through the drain hole from above. Underneath, fit the rubber gasket, friction ring, and locknut in that order, and tighten until the flange is seated firmly and excess putty squeezes out around the rim. Wipe away the excess.
- 3
Set the Sink in Place and Seal the Rim
For a drop-in sink, apply a continuous bead of clear silicone sealant around the underside of the rim (or follow the manufacturer's instruction — some supply a foam gasket instead). Lower the sink carefully into the cut-out, aligning the drain with the stub-out below. Press down firmly, then install any mounting clips from underneath if supplied. Wipe away squeezed-out silicone with a damp cloth before it skins. For a wall-hung basin, hang it on the bracket first, check it is level with a spirit level, then tighten the wall bolts evenly so the basin does not rock.
- 4
Connect the Supply Lines
Attach the flexible braided supply lines to the faucet tail pieces first — hand-tighten, then a quarter-turn with a spanner. Connect the other ends to the isolation valves the same way. Do not use PTFE tape on compression fittings; it is only needed on threaded (BSP) joints. Check that neither line is kinked or under tension, which will cause the fittings to weep over time. If your faucet has a single supply (mixer with one inlet for a pre-mixed hot/cold), confirm you have the correct single-inlet supply line before finishing.
- 5
Assemble the P-Trap and Test for Leaks
Slide the P-trap onto the drain tailpiece and the horizontal waste pipe into the wall stub-out. All slip-joint connections should be hand-tight plus a quarter-turn with pliers — overtightening cracks the plastic nut. Open the isolation valves slowly, let the basin fill, then pull the drain plug and watch all joints — supply lines, drain flange, P-trap, and wall stub-out — for any drips. A dry tissue held under each joint for ten seconds is the most reliable test. Tighten any weeping joint by half a turn at a time until the drip stops.
Rather have a pro handle it?
Get a vetted plumbing pro in your city — one number, booked in EN/EL/DE.
FAQ
- Do I need a licensed plumber to replace a bathroom sink in Greece?
- For a simple like-for-like basin swap that does not move any pipework, Greek law does not require a licensed plumber (υδραυλικός) and the job is firmly within DIY territory. However, if you are relocating the drain stub-out, extending supply pipes inside the wall, or working on a commercial property such as a hotel, you should use a licensed professional to ensure compliance with building code and your insurance policy.
- What type of sealant should I use around a drop-in sink in Greece?
- Use a neutral-cure silicone sealant rated for wet areas (σιλικόνη υγρών χώρων). Avoid acetoxy (acid-cure) silicone on natural stone countertops — it can stain marble and granite, which are very common in Greek bathrooms. A white or transparent sanitary silicone is the safe default for ceramic, acrylic, and stone surfaces alike.
- My building has very low water pressure from a roof tank. Will a new faucet work properly?
- Yes, provided you choose a faucet rated for low-pressure use (typically marked 'suitable from 0.5 bar'). Standard ceramic disc cartridge faucets work from about 1 bar upward. If your roof-tank pressure drops below 1 bar, consider a small in-line pump booster installed on the cold supply; these cost around €80–120 at Greek plumbing merchants and are a common upgrade in older island villas and apartment buildings.