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In general, water is conveyed by private or communal companies to your meter. From this point on, the installation and maintenance of the pipes is your responsibility.

The water is distributed under a pressure of about 3 bars and the entire installation is sized to withstand this pressure.
Depending on the geographical area and the situation of the house (at altitude or at the end of the network), the pressure can vary:

  • If 2 bars are still sufficient for a domestic installation, you can install a booster to increase the capacity.
  • But from 5 bars, the piping may deteriorate prematurely; the installation of a pressure reducer is then recommended.
  • The flow delivered by the different points of watering (taps, plumbing fixtures) depends on this pressure and the section of the pipes which feed it. The larger the pipe, the greater the flow of water.
    Under a pressure of 3 bars:
    • A pipeline of 10 mm of diameter delivers 50 liters per minute.
    • A pipeline of 16 mm of diameter delivers 160 liters per minute.
    • A pipeline of 20 mm of diameter delivers 250 liters per minute.

All fixtures do not need the same flow of water. It can be strong in a shower or garden water tap: we will connect these points by pipes of large diameters.
On the other hand, a wash-stand or a flush of water are satisfied with a much smaller jet: the supply pipes will be of a small diameter.
The following diagram shows the minimum inside diameter of the pipes to be provided for your plumbing installation to work properly.
For more comfort, you can use pipes of greater diameter on some equipment (shower: Ø 14, tub: Ø 16, washbasin: Ø 12).

Copper plumbing: what pressure, flow, diameter?: copper

Pipe diameters

copper tube 14x1

On the pipes, the outer diameter of the tube and the thickness of the copper are clearly visible.
Our example: 14 x 1 indicates that the tube has an outside diameter of 14 mm and a thickness of 1 mm, ie an internal diameter of 12 mm.
This hose can be used to power a sink or bath.
The former name "12/14" still found indicates that the pipe has an inner diameter of 12 mm and an outer diameter of 14 mm.

Fittings: what size for which diameter

The screw connections are the indispensable intermediaries between the pipe network and the sanitary equipment (tap, boiler...). They are classified according to the size of their thread.
for example 15 x 21 means that the diameter of the fitting is 15 mm inside threading and 21 mm outside.
Depending on the sanitary equipment to be connected and the diameter of the tube that distributes the water, use fittings of different sizes (example: for a 12 x 17 thread, use a tube with a diameter of 8 to 14).

Thread and diameter of copper tube

Video Instruction: Water pressure, flow, and pipe size - 1