A valve is a device or natural object 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 swings down to obstruct fluid (gas or liquid) flow in one direction, but is pushed up by the flow itself when the flow is moving 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 aerosol spray cans have a tiny valve built in. Valves are also used in the military and transport sectors. In HVAC ductwork and other near-atmospheric air flows, valves are instead called dampers. In compressed air systems, however, valves are used with the most common type being ball valves.

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  1. S

    'Loose' ceramic valves

    I've replaced the ceramic valves on my kitchen tap, but the new valves are freer turning than the old, and the levers move down from a partial open position under their own weight. I've not had this before - is it duff new valves?
  2. T

    Stopcock/valve advice please

    Hi everyone, I've joined the forum today as I've found myself going round in circles with what I think might be a pretty simple problem, hoping someone can help. Our dishwasher is leaking and the manual says this can be fixed by cleaning the water inlet filter. To do this, we need to close the...
  3. W

    Help - advice on installing shut off valves for basin

    Looking for advice please, our plumber has left us in it and I think I may know why. So they where supposed to be fitting a cloakroom sink putting the pipe work in the wall then fitting these black shut off valves and black trap but can’t see how this is possible the way the work has been...
  4. T

    Turning Water Off When Going Away

    I recently read a post / comment whereby there was a recommendation that if you are away from your home more than 24 hours, then you should turn the water off to avoid potential catastrophic damage. When I go away I have always tended to turn ours off, that's typically anything from a couple of...
  5. B

    Thermostatic valves dont adjust the temp

    the majority of my radiators have thermostatic valves. Some of these work fine but some of them dont let you adjust the temp. ie. Setting one or setting 5 makes no difference - the radiator is blazing hot. For small bedrooms this is pain cos the room just heats up too much. we first...
  6. J

    Draining vokera combi boiler 2 drainage valves on different radiators.

    Hi, I need to drain my vokera 29 boiler in the attic as Im going away for 4 weeks at least to make sure there are no frozen pipes. In my small 3rd floor flat, I have a radiator in the front room and one in the hall (very close to each other), there is a drainage valve on one of these. My back...
  7. M

    Composite valves unvented cylinder

    Do most composite valves now for unvented cylinders have a tee on them For the expansion valve connection? The ones I used to fit just had the balanced cold connection coming of it. Them I tee'd off downstream of the composite valve for the expansion
  8. H

    90 ° Isolating Valves

    Can anyone please tell me where I might purchase a 90° bend 15mm x 22mm Isolating Valve Thanks and Regards. Hugh
  9. P

    Replacing a radiator and Valves

    Hi All, I need to replace a radiator in the kitchen, the 10mm copper has split so using this opertunaty to replace it with a towel one and also need to remove both valves and make the pipes shorter. Its a gravity fed system and the last radiator in the system , I have a bung kit, i know i can...
  10. B

    Replacement Cistern flush valves

    My toilet flush valve is continually draining (the rubber seal has perished) . . . I'd be grateful if someone could give me a link to parts that will fit in there and replace the current valves?
  11. D

    Tempering Valve - Best Brands

    So my hot water tank is barely 3 years old and a recent service check tells me the tempering valve is on the way out It's a Hydroboss brand from Tradelink and I'm keen not to replace crap with crap So what are the best brands of valves on the market ? The plumber recommended AVG
  12. M

    TemCon temperature balancing valves

    I have TemCon balancing valves fitted on my sits and a questions been asked whether these require servicing. Can't find much info on the manufacturer website so can anyone confirm if they do and if so what level of service is required?
  13. Kolash

    Faulty actuators or valves?

    Hi I have a 4 zone / 7 loop UFH system. 2 zones (4 loops) always get hot when the system is on when the zone thermostats and actuators are off. The video posted shows when I turn on another zones the flow meters drop. (Kitchen prep and kitchen TV are the issue, two at either end of the...
  14. W

    Old radiant heater system bleed valves

    Hi, I'm in New Mexico US... I have a fifties boiler with floorboard radiant hydronic heating. The old valves are corroded and not working. I have found a bushing valve combo that has same threading but different profile. Please anyone knows of source for old valve types... Or, can the new...
  15. M

    Motorised valves from China

    I have tried hard to get similar to the first class satchwqell /Sunvic SML type revolving type valves instead of the quite short lived spring return type valves. I saw an advert from the Hearken company who either make these or buy them in. The only problem they are BSP threads so adaptors are...
  16. T

    Mixer taps and check valves

    Hello, I have a few mixer taps to install in bathrooms and kitchen. The kitchen tap also has a wondering spray arm capability. On researching something else, i stumbled across people saying that a check valve should be placed on the cold mains feed. How can I tell if the mixer taps/spray arm mix...
  17. E

    URGENT thermostatic controller on radiator replacement advice needed

    the thermostatic controller has snapped off the top of one of the radiator valves is the threaded metal collar standard to all valves? Can I fit one fro a different make?
  18. oscarwplumbing

    Changing/fixing a bunch of seized imperial and metric valves

    Hi everyone, I'm new here! I've bought my first house - needs a fair bit of work doing to it, including the plumbing. I'm keen to do stuff myself rather than getting contractors in, wherever possible, not just for cost, but also because I want to learn (a useful life skill surely!) I'll...
  19. T

    What Isolation valves are best

    Hello, Is it ok to use a full bore isolation valve to isolate a hot and cold feed to taps or should I use a service restricted bore. I’m thinking about using a full bore with a handle as my default as I find that most of my customers struggle to muster up a screwdriver to isolate the water when...
  20. Naseemkhan1682

    Stop Valves for LDC 50mm Connection

    Hello, I received an offer from the Water Board for a LDC MDPE 50mm connection. We are currently laying the works required in our boundary. A stop valve is required for the external meter chamber but we are unsure which type to buy? There are many available online with substantially...
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