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A valve is a device that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fittings, but are usually discussed as a separate category. In an open valve, fluid flows in a direction from higher pressure to lower pressure. The word is derived from the Latin valva, the moving part of a door, in turn from volvere, to turn, roll.
The simplest, and very ancient, valve is simply a freely hinged flap which drops to obstruct fluid (gas or liquid) flow in one direction, but is pushed open by flow in the opposite direction. This is called a check valve, as it prevents or "checks" the flow in one direction. Modern control valves may regulate pressure or flow downstream and operate on sophisticated automation systems.
Valves have many uses, including controlling water for irrigation, industrial uses for controlling processes, residential uses such as on / off and pressure control to dish and clothes washers and taps in the home. Even aerosols have a tiny valve built in. Valves are also used in the military and transport sectors.

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  1. R

    Shower arm diverter valve

    Hi all I'm trying to add an all metal/brass shower arm diverter valve to have a shower head and handheld. There are many different valves on the market but I couldn't find any that would not restrict the water flow. Here are some pictures (with reviews) I got off of Amazon to show you what I...
  2. M

    Rubber or fibre washer fill valve connections

    Any one started using rubber washers on copper tap connectors instead of fibre?
  3. B

    programmable thermostat to control a Mixer Valve.

    I want programmable thermostat to control a Mixer Valve. This to provide CH flow temperature from 30C to 70C from a thermal store tank at 80C
  4. M

    Looking to find the correct radiator valve type

    Hi, looking to replace a leaking radiator valve onto an existing radiator. Pipe coming up from the floor is 15mm and then the bit connecting to the radiator looks to be 22mm. Can’t seem to find the correct fixing? I thought maybe a reducer would work onto the radiator for a more standard valve...
  5. A

    Drip Drip!! Ceramic Disc Valve

    See attached pics of our quarter turn ceramic disc kitchen tap, which needs a new ceramic disc valve. It is circa 20 years old, and I believe was a popular model with kitchens supplied by Magnet and the like, and that there are still a lot of them around. To save me hawking the old ceramic disc...
  6. J

    Leaking washing machine tee valve

    Hi, Recently moved into a house and the valve on the washing machine tee does not close properly and is leaking. I do not want to remove the whole tee section if possible, I just want to screw an extra section onto the end of the tee with a working valve - but I can't find the right part...
  7. K

    Central heating not working 3 port valve?

    Hi all, Not posted for some time but come up against a small problem. Been off the tools for many years now but I think I know the issue but looking for some reassurance Boiler isn't firing when programmer and room stat is calling for heating, but does for HW. It's a Y plan system, new house...
  8. L

    Air Admittance Valve question for bad smell

    Hi Everyone, We have a new house that may not have been piped correctly. There is a sewer smell in the laundry room and I am thinking of adding an air admittance valve to the standpipe in the laundry room since I do not know if the drain is connected to a vent pipe. Would that be okay to do to...
  9. R

    Combination Valve Installed Correctly?

    Hi, I have an unvented cylinder with a water combination valve before the inlet. It has been installed with the "balanced" cold water feed coming straight off the combination valve and not after it. Is this installed correctly? If not, what are the consequences of this connection? Many thanks!
  10. Y

    Tre Mercati "Marina" Shower valve too stiff

    I have an obsolete Tre Mercati "Marina" shower valve. Replacement cartridges not available. The inner, temperature control knob works OK but the outer, flow control, is a bit too stiff for my partner's arthritic wrist to turn off easily. The manual says to soak the cartridge in vinegar. I can't...
  11. B

    New washing machine water valve issue.

    I recently fitted a new washing machine along with a new cold water feed hose. Since installation whenever the toilet upstairs finishes filling, the shower is turned off, the cold water tank in the loft stops filling or the kitchen cold tap is turned off, there is a clunking noise coming from...
  12. S

    Leaking from the top red valve?

    Can somebody tell me what this part is as it's leaking from the red cap. Is it easy to replace?
  13. A

    Do I need a Durgo Valve

    Hi appreciate some advice - whether or not I need to install a durgo valve In a new downstairs bathroom.. the soil for the downstairs connects to the old soil for the upstairs which (as it’s an old house) the stack terminates above the roof line. my uncle keeps on banging on about regs...
  14. P

    Why does the valve have two pressure relief nipples?

    Any ideas why the pressure relief valve on my water heater has two outlets? Is one inflow and one outflow?
  15. C

    Help - valve isn't twisting!

    Hi lads, I have a tricky situation with a shut-off valve beside the toilet. Water is dripping from the pipe. No water is pouring into the cistern. I can tighten and untighten the nut but I can't twist the valve too much regardless of whether the nut is very tight or very loose. I can attach...
  16. M

    Changing concealed shower valve

    Hi I just wanted to ask if turning the mains water off will be enough to allow me to clean / change an existing concealed shower thermostatic cartridge without any flooding. I have a Glow Worm condensing boiler with a cold water tank in the loft and and hot water cycling in a cupboard (first...
  17. Meady

    Honeywell 22mm V4043 2 port zone valve for sale

    I have 11 of the above for sale, all are brand new and in the original box. Looking for £40 each posted for them. Cheers 1596736173 10 already sold, just the 1 left now. Cheers
  18. S

    Old TRV Valve connection

    I have a tiny leak coming from the underside of the "nut" at the top of the copper feed pipe on an an old Valiant TRV valve . It probably just needs a tightening or a bit of PTFE . I understand that these are usually compression fittings but I think this might be something different as the way...
  19. S

    3/8” 20 spline ceramic valve

    Can anyone help me please . ive been searching for a 3/8” ceramic valve for my bathroom tap and nowhere seems to stock them anymore. It’s a mini valve (41mm) with 20 spline 7.5mm . photo attached from when I purchased one a few years back. Any help really appreciated. james
  20. P

    Aquatronic 2 Plus - slight leak from Stabiliser valve assembly

    Hello, our shower has started to seep a few drips from the stabiliser valve assembly (P07810800) but not from the top where the plunger is which appears to be where they can normally leak from. I've seen you can buy as gasket kit for this area. Ours is leaking from where the temperature control...

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