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. J

    Need advice on how to turn off cold water value to washing machine

    Hello, I need to disconnect my washing machine for several days however i am confused on how to turn off the cold water flow to the washing machine. I have taken a photo. There is no lever from what i can see. Do anyone know what i need to do with this?
  2. B

    New tail for old Peglers Radiator Valve

    I need to replace a radiator, one of the valves is a Peglers B.S 2767 the tail in the old Rad is proving very difficult to remove can you still get tails for these valves? As replacing the valve will involve a lot of work I have a Wicks 15mm x 1/2" valve but the treads appear to be different.
  3. B

    Stopcock and Gate Valve position Query

    Good morning, I would appreciate any advice on the following: I live on the 2nd floor (top floor of building) and have a stopcock under my kitchen sink, one stopcock for water near the boiler in the kitchen and in the hallway in a high cupboard a cold water feed red gate valve. I want to know...
  4. E

    Will reducing pressure by using a device's valve hurt it over time?

    I have this valve. I can reduce the pressure by turning it half way closed. Will that hurt the valve over the long run? Thank you.
  5. gingalig

    Non return valve on unvented

    Hi, thanks in advance for any advice, I've come to change a manifold for the ufh, I have noticed a non return valve on the main dhw outlet on the unvented cylinder Is this acceptable ? 1570704464 My thoughts are no it's not.
  6. D

    Advice needed on radiator valve

    Hi all, this is my first post so hoping I've got it in the right section. I'm a casual DIYer so this may be a simple question to most.. looking to replace the old head on the photo for a new TRV head. Do I simply need to undo the nut at the top & slot a new head on or does the old fixing need to...
  7. D

    Victoria Plumb Milan triple shower valve

    Hello guys, have any of you fitted a Victoria plumb triple concealed shower valve with a fixed shower head and shower hose at lower level. Trying to do a first fix in a stud wall and valve is ok it can be set between 75mm and 90mm from finished surface. However the fixed head and hose part...
  8. S

    Three way valve letting by. (it's a Danfoss).

    It's happened before a few years ago and I changed the complete thing - valve body and actuator. Straight swap, Danfoss for Danfoss. But, now, after the heating has been off all summer, a couple of the adjacent rads get slightly warm when the hot water is on, so presumably the rubber seal in...
  9. J

    External Stop Valve

    Hi, My external stop valve is located in my rear garden. It is under ground and very old (1970). I am building rear extension and It will be in new extension. My water line is a shared line that provides water to 2 properties before and 1 after my property. I have been trying to locate the...
  10. Stefromthewirral

    Double Check Valve on incoming mains

    Hi all, I have two questions that I'm looking for advice on please? 1. I've been asked to fit a double check valve on a new incoming main. I only did my water regs last year and this wasn't stipulated in the reg's? Has this now changed or did miss something? The property in Cheshire. The main's...
  11. Christopher buzzard

    Thermostatic rad valve.

    Evening All. Can any1 provide a link for a thermostatic radiator valve and head which is suitable for a 1 pipe heating system. I know danfoss but was unsure of the model number. thanks in advance
  12. BobThomas

    Valve fitting orientation... horizontal / vertical ?

    Dear all, i’ll get this out of the way first... I’m not a plumber, however i’ve done a fair amount albeit a long time ago (in a galaxy far far away), and i’m after a bit of ‘best practice’ advice, apologies if this is perhaps a daft question ! When fitting, for example, a full-bore pegler type...
  13. F

    Advice on Sunvic 3 port valve

    Hi All, I'd like to swap my Sunvic 3 port motorised port for a Honeywell. The issue I have is that the Sunvic has 4 wires and the Honeywell has 5? Anyone know if this can be done? Thanks
  14. V

    How do I open this blue valve please?

    I believe this is the inflow valve under my ideal mini boiler. The bar lever is around 0.5 which I think is why the central heating keeps clicking off after about 5 to 20 seconds. I need to top it up to about 1 bar but I don’t know how to open this valve because if I try a twist it is stuck...
  15. Z

    Honeywell bypass valve possibly not well

    After x number of years, I looked at this valve as the water was very hot very quickly through the valves. It was set to the white band which didn't look correct. I unscrewed the screw to reset it. It fell out and revealed three loose parts Screw, red cover, and black part with the numbers...
  16. I

    Manufacturer of Radiator Thermostatic Valve

    My bathroom radiator has a damaged Thermostatic Valve. I took it to a local DIY firm to look for a replacement. They informed me that I would need to know the manufacturer as different companies have different style connectors. I have attached a photo which shows the valve & connector. Can...
  17. P

    Anyone know who makes this thermostatic shower valve?

    Has no manufacturer markings at all. Thanks.
  18. D

    Help requested to discover the make of this shower valve

    Hello all, A couple of years ago a plumber installed the shower valve in the photos. It is now broken and I need to change the cartridge. Unfortunately he has since had an accident and so I can't contact him to find out the make/model so I can replace the cartridge. A plumber has come and...
  19. J

    Faulty new Honeywell valve?

    Hi guys just exploring a possibility I’ve replaced a 3 port valve and it’s passing into the heating circuit when hot water is on. Could an electrical fault cause this problem? There is no call for heat on the heating circuit, proved with my multimeter. The heating pipe work next to the valve...
  20. A

    Unknown Thermostatic Cartridge

    Hi Guys, I have a leaking thermostatic cartridge and I'm trying to replace it but I cannot find the part number or any no-name ones with similar measuring. I bought the shower from Victorian Plumbing and it is the Milan Modern Thermostatic Shower in Chrome. It was bought in 2015 and their...
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