Non Return valves confusing information

[gardener1214388]

I'm fitting mixer taps to basin & Bidet.
Each tap is supplied with two separate flexi pipes for assembly.
Manufacturer's leaflet says fit non return valves to hot and cold pipes.
Manufacturer's tech dept says fit only to cold pipe
One internet video; plumber says fit only to hot water pipe.

I intend to also fit an isolation valve to basin, bidet and pan supply pipes for maintenance with a non return valve below them.

I've also searched UK Water regulations, not yet found a simple diagram for non return valve positions, must be available though.

Does anyone know where a single none return valve should really be fitted.

 

[muggles]

The answer is "it depends" to some extent, as you haven't revealed what kind of hot and cold water system you have...

Let's start with your basin. If that is fed by mains-pressure cold and low pressure hot then you'd definitely need a double check valve on the cold, and may wish to have a single check valve on the hot to prevent cold being forced back up the hot supply. If you have low-pressure supplies on both sides then no check valves would be needed, assuming that both are fed from the same loft tank, or at least from loft tanks at the same height. Fit any required check valves after the isolation valves so that the check valves can be maintained

Bidets are slightly different as they are covered by different regulations. If your bidet has an ascending spray, or a hose attachment, then it must be tank-fed with its own dedicated supply pipes. It is not permissible to connect it to the mains under any circumstances, nor it is permissible to tee it into the low-pressure supplies for the basin on either the hot or the cold side. You need a separate feed from your loft tank for the cold, and a dedicated connection from your hot water cylinder (an Essex/Surrey/Warix Flange). No additional backflow protection will be required provided your loft tank has the correct type of float valve and the correct overflow arrangements.
If there is no ascending spray or hose attachment then it can be fitted to the mains in the same way as a basin, provided the correct type of tap is fitted; IE, it must be a tap designed for a bidet and not a tap designed for a basin.

Hope that helps!

 

[Nozzle]

Depends on the pressure of your hot and cold systems. If the hot is gravity fed and the cold is mains fed then it's unlikely that the hot system will ever have enough pressure to contaminate the cold side.

Nozzle

 

[muggles]

Depends on the pressure of your hot and cold systems. If the hot is gravity fed and the cold is mains fed then it's unlikely that the hot system will ever have enough pressure to contaminate the cold side.

Nozzle

Nevertheless, water regulations require that you protect the cold so that hot can't be drawn in in the event of a mains failure such as a busy pipe