Plumbing and Domestic Water Supply in France

What you need to know about the high calcium content of the water, the water pressure, copper and PVC pipes and joints and common plumbing problems in France…

This INFOrmation Page provides an advice on French plumbing to cover frequently asked questions and common problems encountered with systems and equipment. No reference is made to the statutory regulations with which a home owner must comply; a plumber will be familiar with the water regulations and will install systems in compliance.


The pressure of the water supply in France is relatively high, a water pressure of 6 bar is quite normal. The incoming water supply pressure should be regulated at the entry to the property to 3 bar by installation of a pressure reducing valve.

The pressure reducing valve can be installed in the meter pit at the boundary of the property or immediately after the entry of the main water supply in to the house. There is no internal water storage tank with a ball valve (as is commonly found in properties in the UK).

High calcium water

Water quality varies from region to region but, with a few exceptions, tends to be hard with high calcium content with the result of limescale deposits on everything from kettles to sanitary ware. In high calcium regions (the department of Aquitaine, for example), an anti tarte device is considered essential, and the minimum level of water treatment to be installed.

  • The anti tarte device does not remove the calcium deposits but effectively ensures the particles cannot stick to the surfaces of pipework and appliances. Effectively the build-up of limescale is reduced or eliminated which means a longer life for the systems and equipment. This device does not alter the quality of the water supply but is a good compromise which offers value for money protection.
  • Water softener equipment can provide total protection and optimum water quality. This equipment eliminates limescale and supplies soft water good for washing clothes and bathing. 
    Water softeners can be expensive and if they are to be effective they must be selected according to the water demand in the property and not solely on the basis of cost. Water softeners also require periodic maintenance and regeneration to keep them operating efficiently. 
    Note: the drinking water supply (normally the kitchen tap) should bypass the softener. Calcium is essential for health and hard water is the best water to drink. An alternative is to install a separate drinking water tap and allow all domestic water to pass the water softener.

Materials and Equipment

Materials used in plumbing installations tend to be the same throughout Europe but there are significant differences in the diameters of copper pipework and methods of bending due to differing hardness of the pipe.

The simple rule is when in France use French sourced materials and then they will be suitable for installation and, particularly connection to existing services. The only thing that is universal throughout Europe (and the UK) is the screwed threads which are all British Standard Pipe Threads.

With modern materials such as multicouche (multilayer) pipe the tube and fittings tend to be universal and generally can be used in any country without problem. Ensure that modern PVC and multicouche systems are installed using the manufacturer’s specially designed fittings. These fittings are installed using specialised tools to compress and deform the joint. Under no circumstances should these systems be installed with any other type of fitting. For example, if copper compression fittings were used it is likely that the joints would blow apart after a period of time.

PVC materials used for drainage, soil and waste pipes are the same throughout Europe and can be used anywhere. Note that all PVC pipes, unless specifically designed as push fit, must be glued with the correct solvent weld cement to effect a proper installation. It is quite common in France to encounter installations where waste pipework has been assembled unglued, with the consequent risk of leaks and a potential health hazard.

Copper tube is still the most widely used material for pipe installations and the most secure method of jointing is with soldered joints. A properly soldered joint should never leak whereas there is a risk of leakage with mechanical compression couplings. A professional will only use mechanical couplings where future disconnection may be required for maintenance or replacement.

Equipment supplied in France is designed to accommodate the water supply pressure. Ball valves and taps operate correctly when installed where they have been designed for the local supply pressure. To ensure optimum performance of plumbing installations and avoid wastage of water only use French sanitary ware and plumbing equipment.

Common Problems

Several problems with French plumbing are frequently encountered and in the majority of cases can be simply and easily overcome.

Groupe de Security

By far the most frequent problem encountered is with the Groupe de Security. This is found on the cold water supply connection to electric water heaters and hot water storage tanks in heating installations.

The problem is that the valve is constantly running to drain.

The valve itself serves a triple function, a shut off valve, a drain valve and a pressure relief valve and it is the pressure relief function that is at the root of the problem of constant discharge. The valve is preset to discharge at a pressure of 7 bar. This is a safety device to protect the equipment in the hot water system and should never be blocked or tampered with. Therefore if the valve is discharging it is most likely that the system is above the maximum operating pressure of 7 bar. As the water heats it will expand and system pressure will increase if there is no open outlet to release this pressure.

In most cases the proper pressure regulation of the incoming mains water supply will solve the problem; alternatively the installation of an expansion vessel will absorb some of the pressure increase and prevent discharge from the valve.


Water constantly dribbling into the WC pan: generally this is caused by the ball valve or possibly a worn/badly seated washer in the siphon. WC suites in France generally have internal overflows; the siphon is designed to allow water to escape via the siphon if the water level in the cistern reaches too high a level. If the ball valve is worn so it does not shut off, or is badly adjusted then the result will be the constant discharge of water in to the WC pan.

Stopcocks and valves

Stopcocks and valves can stick and not work when needed to shut off water supplies. In the majority of cases this can easily be prevented by simply opening and closing the valves periodically.

When operating a valve, never leave it fully open; always close the valve back a quarter of a turn to prevent hard contact between metal surfaces.

Water hammer

Water hammer is the noise and severe vibration resulting from high water pressure. The cause is normally a loose tap washer, unstable ball valve or badly supported and clipped pipework. If the problem cannot be located and eliminated at source a small damper can be installed to absorb the hydraulic shock and prevent the problem.

Macerators (Sanibroyers)

In common use and often problematic: invariably the cause of problems with this equipment is incorrect installation. This equipment should only be installed by a professional to ensure both correct installation and compliance with French regulations.

Waste Pipe diameters

Generally, throughout Europe, the following size diameters can be expected waste pipes from appliances:

  • WC/toilet: 100mm (or 10cm. This is the standard toilet drain size)
  • Bath, shower and sink:  40mm
  • Basin, bidet: 32mm

In a standard domestic dwelling a 100mm diameter drain runs from the house to a septic tank or mains drain. Early French properties typically had cast iron waste drains. This was phased out and replaced with PVC plastic in the early 1960s.


Winter in some parts of France can be very severe and frozen and burst water pipes are a real problem.

  • Ensure that all exposed pipework is properly insulated and protected against freezing
  • All external supplies should be valved so that they can be isolated and drained for the winter

Houses left empty during winter

If a property is left unattended for a few days or a prolonged period the water supply to the house must be turned off; this will ensure minimal water damage in the event of a freeze and subsequent burst.

  • After the water is turned off, open taps and drain cocks to drain as much water as possible.
  • Turn off electric water heaters (this can usually be done at the main switch board or there may be a local fuse near the heater).
  • A central heating installation remains full of water and needs to be protected by low temperature detection to activate the heating in freezing conditions. Frost detection is installed on the majority of modern heating installations. For internal temperature detection set the temperature to 6º Celsius and for external temperature set to 0º Celsius.
  • Do not switch off the electricity supply, doing so means the boiler will not operate and there will be no protection in the event of freezing conditions.

Hiring Experts

A plumbing or heating system must be properly installed by a qualified and insured artisan. Copper pipework needs to be soldered for a professional standard of work and modern multicouche and PER pipe systems need specialised and very expensive tools for jointing.

Plumbing or heating artisans must be registered and fully insured. Get references and check them, ask to look at his work. A good artisan will be happy to comply with this request.