Backflow valves necessary for mixer taps?


Postby cobweb181 » Fri Feb 22, 2008 9:27 am

Are backflow valves really necessary on pipes for a kitchen mixer tap?

I have ground floor standard mains cold water, a hot water tank on the first floor and a large cold water storage tank in the loft. Cold water pressure is 4 bar and hot water pressure at least 1 bar. I bought a Damixa Architect tap from B&Q which I was assured was suitable for my water supply but when I got it home, the info inside the box said not recommended for this type of water supply unless a backflow valve was inserted in both hot AND cold water supply pipes.

Are both really necessary and what's the reason for having them anyway if the cold water is high pressure?

Where about along the pipe should it the valve(s) be placed?

There already is a ball valve on the cold water pipe just inside the house, can this be used to control the pressure instead?

Also, are left hand flexibles available? I was hoping to use flexibles with the tap instead of the copper pipes supplied but turns out they are left hand threaded.

Sorry for all the questions, I'm tempted to either just put the thing in anyway and see or return the damn thing!
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Postby ALDA » Fri Feb 22, 2008 4:30 pm

DOES THIS MIXER TAP HAVE A FLEXIBLE EXTENSION PIPE THAT REECHES INTO SINK?

IF IT DOES, THEN THIS IS WHY BACK FLOW VAVLES HAVE TO BE FITTED.

THE VALVE IS THERE TO PREVENT USED WATER BEING DRAWN BACK INTO SUPPLY PIPES.

NO MATTER HOW UNLIKELY IT MAY SEEM THAT THIS COULD HAPPEN THERE REMAINS THE POSSIBILITY AND IS REQUIED BY WATER AUTHORITIES/SUPPLIERS.

FIT AS CLOSE TO THE NEW TAP AS POSSIBLE/ACCESSIBLE.

THEY ARE NOT A PRESSURE CONTROL DEVICE. "AS IT SAYS ON THE TIN" THEY ARE AN ANTI BACK FLOW DEVICE(ONE WAY VALVE)(ANTI SYPHON VALVE) ARE OTHER NAMES USED.

THE BALL VALVE??? THAT YOU MENTION IS PROBABLY AN ISOLATION VALVE OR STOP COCK AND THESE ARE THERE TO PRVIDE A MEANS OF SHUTTING OFF THE WATER SUPPLY( NOT TO CONTROL PRESSURE) WHICH YOU DONT NEED TO DO ANYWAY.
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Postby cobweb181 » Sun Feb 24, 2008 2:34 pm

The tap I purchased has 2 versions, the more expensive one has the extension pipe. I opted for the cheaper one without, hoping to be less hassle.

Does this mean I can do without the additional valves?
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Postby Skids » Sun Feb 24, 2008 4:39 pm

Hi Cobweb 181,

The wonderful world of backflow regulations!! :lol:

1. Look up the spout, does the mixer tap have:

a. ONE hole at the spout? - the hot and cold water is MIXED in the body on the tap, (single-flow outlet), or

b. is the outlet divided in TWO, or have a central exit (hot water) with the cold coming out around the hot, – hot and cold NOT mixed in the body of the tap! (twin-flow outlet)

If the answer is (a) there is a possibility that: if whilst you are running both hot and cold waters, ‘IF’ the rising mains water pressure was for some reason to fail, the hot water (contaminated) could ‘flow back’ into the ‘rising mains’ and contaminate the main water into the next house, lovely cup of tea!

There is also a chance that with 4bar of cold and 1bar of hot that you will not get an even mix of the hot and cold water, or cold water being pushed into the hot distribution pipe.

Always purchase mixer taps that have separate supply pipes up the spout and do not mix in the body of the tap, the ones called ‘Twin-Flow Outlet.

Double check valves cost under £5 and must be of at least ‘Fluid Category 5’ standard and should be fitted ‘at point of use’ as Alda said.

The other ‘backflow device’ you have is the ‘air gap’ which is between the end of the tap spout and the water level in the sink, and again as Alda mentioned, if you fit a flexi hose type fitting onto the tap which may/could/will dip into the water, you break the ‘Water Regs’ by allowing contaminated water to be drawn into the rising mains pipe if there were to be a drop in mains pressure.

They charge all that money for clean drinking water and don’t want it made mucky. :x See the ‘Water Supply (Water Fittings) Regulations 1999’ Schedule 2 Paragraph 15, for some stimulation bedtime reading. :roll:

Ball valve (Spherical Plug Valve), the key is in the name of the fitting: the ball refers to how it closes, the stopping bit is a ball with a hole (port) going through it, when the ball is turned the hole moves around 90° and the bit of the ball without a hole fills the pipe. It is not a pressure reducing device, the misconception is that by shutting a stop value you reduce the pressure, here you need to understand the difference between ‘pressure’ and ‘flow’, and that is another can of worms better left closed.

Regards

Skids
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