Kitchen Tap

[Reg]

Have bought a new mono-bloc tap to install. Instructions say 'If fitted to low pressure hot water and high pressure cold supplies, non-return valves must be fitted to each and a flow restrictor fitted to the cold'. I would have thought most kitchen installations were like this. Can someone kindly tell me what they are and where precisely, they are fitted. Thanks in advance.

 

[breezer]

Have bought a new mono-bloc tap to install. Instructions say 'If fitted to low pressure hot water and high pressure cold supplies, non-return valves must be fitted to each and a flow restrictor fitted to the cold'. I would have thought most kitchen installations were like this. Can someone kindly tell me what they are and where precisely, they are fitted. Thanks in advance.

If you have a combi boiler (as i have) the the water pressure of each is the same (almost) as the hot water comes directly off the mains, into the boiler and out to the tap.

What they are refering to is if you have a hot water cylinder which gets its pressure from the height of the tank you have in the loft. what can happen if you have this is that if you turn the cold water on as it is a higher pressure it can go backwards up the hot pipe, so by fitting a non return valve stops this.

A flow restrictor valve reduces the pressure of what it is fitted to, so if you have a tank in the loft you fit one to the cold water side to reduce / even the pressure so the cold can not go into the hot as they will be the same pressure.

in either case they should be fitted between the supply pipe and the tap itself.

Having said that, we have just had a new kitchen fitted and we have no valves at all (apart from isolating ones) this is not only because we have a combi boiler but because of the design of the tap we have. It looks like an ordainary " goose neck swivel tap" but in actual fact there are two pipes inside the tap the hot water comes through the centre and the cold from around this (i just looked to be sure, sad i know)

Imagine a circle with a dot in it ( i cant draw sorry) the cold comes through the circle and the hot through the dot

but i also think ther is some waterbye law that says if there is any chance of back flow you must ffit a non return valve

 

[MANDATE]

Hi Reg.
I agree! drinking water is available only in the kitchen in many houses and is of course directly off the mains suppy and the pressure is consideribly higher than hot water.
Non return valves contain a ball and a spring so liquid can only flow in one direction so once past the ball there is no going back should the balance of pressure change.
A flow restrictor, well that restricts the flow, I turn my stop cock down to restrict the flow, the cold water pressure is that great that with the kitchen tap open fully the water bounces out of the sink.
I would suggest the cold water passes through the non return valve before the flow resistor although I'm not sure if it makes any difference.
I just think if the flow resistor came first the pressure maybe insufficient to open the non return valve. Perhaps the instructions will clarify the point.