Domakihub How to Fit a Washing Machine Stop Tap
Give yourself a proper isolation valve so you can swap hoses and service your machine without cutting the water to the whole building.
Reviewed by Domakihub home & decor pros · 2026-06-23 · 5 min read
A dedicated stop tap (also called an isolation valve or service valve) on the cold-water supply line to your washing machine is one of the most useful small jobs you can do in any home, rental apartment, or hotel utility room. It lets you shut off just that one machine for maintenance, hose replacement, or emergencies — without killing the water supply for the rest of the building. The video above shows the self-cutting saddle valve method on a live 15 mm copper pipe; the steps below cover the full process, including the more permanent compression-tee alternative that professional plumbers prefer in Greece.
Why a Dedicated Stop Tap Matters
Many installations in Greek homes and holiday rentals feed the washing machine directly from the kitchen or bathroom supply branch with no local isolation point at all. When a rubber fill hose degrades — which it will, typically after five to seven years — there is no way to stop the flow without shutting off the whole floor or building. A single inline isolation valve, costing under €10, eliminates that risk entirely.
In hotel and short-let settings the value is even greater: maintenance staff can service or swap a machine between guest stays without any coordination with other units. Greek building regulations do not mandate these valves, but they are standard practice in Northern Europe and increasingly expected by property managers and insurers.
Self-Cutting Saddle Valve vs Compression Tee: Which to Use
A self-cutting (saddle) valve clamps onto an existing 15 mm copper pipe and drills through it without cutting the supply — making it the fastest no-solder option and ideal when a live pipe cannot be isolated. The trade-off is a slightly higher long-term leak risk at the saddle seal; they are considered a temporary or emergency solution by most plumbers and should be inspected annually.
A compression tee fitting — where you cut a short section of pipe and insert a tee piece with an inline isolation valve — is the permanently correct solution. It requires isolating the supply briefly (usually just the relevant branch stopcock), a pipe cutter, and two compression fittings. Neither method involves mains electrical work or gas, so a competent DIYer can do either safely, though calling a licensed plumber is always the prudent choice if you are unsure about your pipe type, water pressure, or access.
Fitting the Stop Tap: Step by Step
- 1
Isolate and drain the supply line
Locate the branch stopcock that feeds the washing machine — often under the kitchen sink, inside a utility cupboard, or at the building's main riser. Turn it fully clockwise to close, then open the washing machine's cold-water hose connection slightly to drain any remaining pressure from the line. Lay dry towels and a small tray beneath the work area.
- 2
Mark and prepare the pipe
Decide where on the supply pipe you want the valve — ideally within 300 mm of where the fill hose connects to the wall, so the hose can reach without strain. For a compression tee: use a pipe cutter to remove 22 mm of pipe cleanly, de-burr the cut ends with the reamer or a small file, and slide the compression nuts and olives onto each end before you forget. For a saddle valve: clean the pipe surface at the chosen spot with fine wire wool so the saddle seats flat.
- 3
Fit the valve body
Compression tee method: push the tee body onto both cut ends, ensuring the olives are seated against the tee shoulders, then hand-tighten the compression nuts before giving them one-and-a-quarter turns with an adjustable spanner — do not over-tighten or you will deform the olive. Saddle valve method: position the saddle halves around the pipe, insert the rubber gasket, and tighten the clamp bolts evenly until the gasket compresses firmly; then slowly wind the cutting needle in clockwise until it pierces the pipe wall (you will feel it bottom out), and back it off a half-turn to the open position.
- 4
Connect the fill hose and turn the water on slowly
Thread the washing machine's inlet fill hose onto the outlet port of your new valve — most use a standard 3/4-inch BSP thread; wrap two to three turns of PTFE tape clockwise around the male thread first for a leak-free seal. Open the new isolation valve (a slotted screw head parallel to the pipe means open; perpendicular means closed), then slowly reopen the branch stopcock. Check every joint and the saddle seal visually for ten minutes while pressure returns.
- 5
Test the valve and label it
Verify the isolation valve actually works: close it and confirm the washing machine shows a water-supply fault or fails to fill. Then reopen it. Stick a small adhesive label on the valve (or on the cupboard door above it) reading 'Washing machine water — turn clockwise to isolate'. In a rental or hotel setting, log its location in your property maintenance record so the next technician can find it immediately.
Rather have a pro handle it?
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FAQ
- Can I fit a washing machine stop tap without turning off my entire building's water?
- Yes — if your building has a branch stopcock for the kitchen or utility room (most Greek apartments built after 2000 do), you only need to close that one valve. In older buildings without branch stopcocks, you may need to close the main building supply briefly; this is best coordinated with neighbours and takes only a few minutes. A saddle valve can theoretically be fitted on a live pipe without any isolation at all, but this is messy and not recommended.
- What size fitting do I need for a standard Greek washing machine supply?
- The supply pipe in most Greek homes is 15 mm copper or 16 mm Pex. The fill hose on virtually every European washing machine terminates in a standard 3/4-inch (20 mm) BSP female nut. You need an isolation valve with a 15 mm compression inlet and a 3/4-inch male BSP outlet — this combination is sold as a 'washing machine service valve' at any plumbing merchant (hydraulika) and at chains such as Leroy Merlin Greece.
- Should I use a plumber or can I do this myself?
- Fitting an isolation valve on a cold-water domestic supply is within the capability of a careful DIYer who is comfortable using a pipe cutter and spanner. However, if your pipes are corroded, soldered rather than compression-jointed, or if the relevant stopcock no longer closes fully, call a licensed plumber — an uncontrolled leak inside a wall or under a floor in a rental property can cause far more damage than the cost of a professional visit.