O/T What does a tap do??

[Rory's Dad]

Yeah I know - it turns the water off and on

but ...

do they just reduce/increase the flow??

and/or

do they also reduce/increase the pressure??

Have a problem with high mains water pressure causing a new fangled single tap in our bathroom to fail by allowing mains cold water into the hot water system within the body of the tap which then backs up into the cold water tank that then overflows.  Diagnosed by hearing slight whistling noise in the tap when it's off.  Got a new one (free from B&Q) and problem solved.  Three months later it's happening again     (although to a lesser extent)

I see that there are 'pressure reducing valves' available but I dont see how they are different from a simple tap??  

Will turning the little valve down on the mains cold water feed to the tap help??

Rory's Dad

[mud]

put a non return valve on both hot and cold behind basin ,cheap and problem solved.iirc taps are supposed to be fitted with anti syphoning valves but i dont know how this will work with mono bloc taps.i think that the tap you have been sold is not  correct  and "not fit for the use it was intended for" meaning any damage caused should be paid for by B&Q

p.s. non return valves are the ones normally used on combi boiler filling loops.Dont turn down your mains pressure just because there tap is not up to the job

[Mrs Westy]

Did the B&Q tap say it was suitable for use with mains water pressure?

[Rory's Dad]

Thanks Mud - I used that line to get the new one and yes Mrs Westy it says the tap should be suitable for both high and low pressure water.

Any more ideas before I go for the non-return valves??

Rory's Dad

[Man On The Clapham Omnibus]

An ordinary tap will not reduce static pressure although the pressure will be reduced once the water is flowing by way of adding resistance. If you think in electrical terms a resistor will not reduce voltage in an open circuit (closed tap) but will cause a voltage drop proportional to the current flowing. To reduce pressure you need, suprisingly   , a pressure reducer with a diaphragm type mechanism in it like those on oxy-acetylene bottles. Historically the cold supply in the bathroom was usually on the cold tank in my experience, not the mains but any tap sold today really ought to be able to cope with widely differing standing pressures IMHO - Mrs Westy is right as usual.  

[Westfieldman]

Its porosity in the tap body casting I had the same problem years ago change the tap for a good one

Mains water presure is around 40psi so not big pressure

the way around it is NRV's but it's not the best way

[Chasmon]

We get over 13bar of mains here thats about 200psi....    Avergae of about 10bar though

Bit of a worry if you get a leak.

Pressure reducing valves work on a principle of only allowing the down stream pressure from the valve to reach a certain point. Before shuttting the flow off. This is the only way of reducing the static pressure.

They are good for over pressure in appliances but not really necessary for taps. Sounds like Westfieldman has hte root of the problem.

[Lurksalot]

We get over 13bar of mains here thats about 200psi....    Avergae of about 10bar though

That sounds a little excessive ..by a factor of about 10

[perksy]

 

Does sound abit high  

Most Water companies are turning the pressure down abit

Because they ain't fixing all the leaks and they're trying to save some water    

Have seen Taps fail due to porosity

Quality ain't what it used to be  

[Chasmon]

Its not pumped here comes from the top of a very tall hil

[pistonbroke]

Not as tall as the story  

[Chasmon]

As measured when we got a water softener rated at 6 bar... Hence the reducing valves

[Rory's Dad]

Thanks Guys - I'll get a non-return valve tomorrow - hope it works  

Not looking forward to getting round the back of the basin again - the space is small and I am big  

Rory's Dad