Domakihub How to Fit a Pressure Reducing Valve and Protect Your Pipes
Control mains water pressure before it damages fixtures, appliances, and boilers in your home or rental.
Reviewed by Domakihub home & decor pros · 2026-06-23 · 5 min read
High mains water pressure is one of the most common hidden causes of dripping taps, banging pipes, and short appliance lifespans in Greek homes, holiday rentals, and hotels. A pressure reducing valve (PRV) is a simple, one-time fix that sits on the incoming supply pipe and brings pressure down to a safe, steady level. The video above shows the job clearly; this guide walks you through the key preparation steps, what to expect on site, and how to confirm the installation is working correctly.
Why Mains Pressure Is Often Too High in Greece
Municipal water supply pressure in many parts of Greece — particularly in hillside areas of Attica, the Peloponnese, and on islands with gravity-fed reservoirs — regularly runs above 6 bar. Most household pipework, boilers, and washing machines are rated for 3–4 bar maximum. Running continuously above that threshold wears out valve seats, stresses pipe joints, and shortens the life of hot-water heaters and pressure vessels.
Holiday rental operators and hotel facility managers face a compounded risk: guests leave taps and showers running at full flow for extended periods, and a burst flexi-hose or split fitting caused by excess pressure can flood a property overnight. A PRV costing €50–€120 fitted at the mains entry point removes that risk entirely.
Choosing the Right Pressure Reducing Valve
PRVs are rated by pipe diameter (typically 1/2", 3/4", or 1" BSP for domestic properties) and by maximum inlet pressure — choose one rated comfortably above your current mains pressure. Adjustable models with a built-in pressure gauge port are strongly recommended: they let you dial in the exact outlet pressure you need and verify it without buying a separate gauge. Brands such as Caleffi, Honeywell (Resideo), and Watts are widely available at Greek plumbing merchants.
Note: the PRV goes on the cold mains inlet — before the boiler, water heater, or any branch feeds. If your property already has a pressure vessel (expansion vessel) or combi boiler, check whether the manufacturer specifies a maximum inlet pressure and set your PRV to that value (usually 3–4 bar). Always isolate and work on the cold supply only — gas pipework and gas appliances must never be touched without a licensed gas engineer.
Fitting a Pressure Reducing Valve: Step by Step
- 1
Shut Off the Water and Drain the Pipe
Turn off the main stopcock where the supply enters the building. Open the lowest cold tap in the property and let water drain from the section of pipe you will be working on. If there is no drain valve, have a bucket ready. Confirm the pipe is fully depressurised before touching any fittings.
- 2
Cut Out a Section of Pipe and Clean the Ends
Using a pipe slice or hacksaw, remove a section of cold mains pipe long enough to accommodate the PRV body plus its tail fittings — typically 150–200 mm. Deburr and clean both cut ends with emery cloth. If you are joining to copper pipe, tin the ends lightly with solder or prepare olive compression fittings; for push-fit, ensure ends are perfectly square and fully inserted to the depth mark.
- 3
Fit the PRV in the Correct Flow Direction
Every PRV body has a flow arrow cast or printed on it. The arrow must point in the direction water travels toward the property — inlet on the mains side, outlet toward the internal pipework. Connect the inlet tail first, then the outlet, using PTFE tape on all threaded joints (minimum 10 turns). Tighten compression or threaded connections firmly but do not overtighten — one-quarter turn past hand-tight is usually sufficient for compression olives.
- 4
Restore Supply and Check for Leaks
Open the main stopcock slowly to allow pressure to build gradually. Inspect every joint around the PRV for drips while the pressure rises. Pay particular attention to the inlet and outlet unions. If you see weeping at a compression fitting, tighten by small increments. Do not leave the installation unattended until you are confident all joints are completely dry under full pressure.
- 5
Set the Outlet Pressure and Verify with a Gauge
Most adjustable PRVs are pre-set at the factory to around 3 bar. To change the setting, loosen the locknut on the adjustment screw, then turn the screw clockwise to increase pressure or anti-clockwise to reduce it. Attach a pressure gauge to the test port (or a gauge tee downstream) and check the reading with a tap open. Aim for 2.5–3.5 bar for most residential and hospitality applications, then re-tighten the locknut. Record the final set pressure and date on a label stuck near the valve for future reference.
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FAQ
- Do I need a licensed plumber to fit a PRV in Greece?
- Greek law does not require a licensed plumber for cold-water pipework modifications in private dwellings, but a qualified plumber (with the relevant OAED certification) is strongly advisable for any mains-connected work. If your building is a hotel or registered tourist accommodation, health and safety regulations may require documented maintenance by a certified professional. Always check with your insurer — some policies require licensed tradespeople for mains supply work.
- What outlet pressure should I set the valve to?
- For most homes, holiday apartments, and small hotels, 3 bar (approximately 43 psi) is the standard target. Combi boilers often specify a maximum cold fill pressure of 1.5–2 bar and should have their own filling loop limiter, but the mains PRV should still be set to protect all other pipework. If you have a rooftop storage tank and gravity feed, a PRV may not be needed on that branch at all — only on direct mains outlets.
- How do I know if I already have a PRV?
- Look at the pipework close to where the mains supply enters the building (often near the water meter, under a sink, or in a utility cupboard). A PRV looks like a bell-shaped or drum-shaped brass body with an adjustment screw on top, flanked by union connections. If you are unsure, attach a pressure gauge to an outdoor tap or washing-machine connection and read the static pressure — anything consistently above 5 bar suggests no PRV is fitted or that the existing one has failed.