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valve

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. R

    Where can I buy this exact isolation/service valve?

    The isolation valve connected directly to our toilet fill valve has started to leak (I assume the washer has deteriorated). I'd like to get a like-for-like replacement so that I can just do a straight swap of the entire isolation valve without having to worry about resizing pipes, but my google...
  2. J

    Thermostatic mixer valve

    I will be taking out my bath and putting a shower tray in. Under the bath there is a thermostatic mixer valve, I can't see ATM but pretty sure it's going to the bath taps, it is about 6 to 8 inches out of the floor boards so will be in the way, is it ok to cut it to floor board level'ish and...
  3. R

    Tankless - Cold Water Hamer Sound with Cold Line Spring Check Valve

    I just had installed a Navien NPE-2 with built in recirculator pump. I have a dedicated return line. The check valve for the recirc is built into the unit; a spring check valve was placed on the cold line (per the manual) after which there is an expansion tank (on the cold line) in a T junction...
  4. Stuartpm

    Straight valve to turn shower on & off (you'd think this would exist)

    Hi - recognise this a bit of an odd one. We have an old failed mixer valve which we need to replace. This valve actually predates a temperature controlled boiler, so the mixing functionality is irrelevant, since the cold water pipe is isolated/off. I'd ideally like to replace the shower valve...
  5. I

    Thermostatic rad valve

    I'm in Canada, where the standard is NPT. I just put in a heat pump and shut off the hand valves but I want the rads in the room to warm up if the heat pump can't keep up. NPT thermostatic rad valves are available but are hellish expensive. The sizes I have are 3/4" and 1". The system used to be...
  6. SteveRobert5a

    Megaflo temperature/pressure valve won't open

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  7. B

    Weak flush - pneumatic button mech or flush valve?

    I have a wall hung pan with a concealed cistern. The flush is the "old style" Grohe Eau2 dual flush pneumatic button. When pressed the flush valve lifts lightly and closes giving a very short weak flush. You can manually lift the flush valve in the cistern and it moves freely, flushes fine and...
  8. T

    Thermostatic shower valve

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  9. I

    Zone valve Flow Direction may be incorrect - Advice required

    Hi, first time plumber and poster here. I've installed two new zone valves and replicated the direction inwhich the original valves were installed. I'm really confused now as I think the originals may have been installed the wrong way round. The Grundfos pumps' arrow is pointing down whereas my...
    • imguessing
    • Thread
    • advice direction flow forum incorrect plumbing required valve zone zone valve
    • Replies: 1
    • Forum: Plumbing Zone
  10. A

    Radiator Bleed Valve - 1/8-27: Thread Type

    Morning all. I hope this is the correct place for this post. If not i'll happily move it to another forum area. I am renovating a property and the old cast iron radiators need a refresh, and i'm going to fit some new bleed valves amongst other things. The female thread in most of the rads...
  11. S

    URGENT Crosswater thermostatic valve

    Hi does any one No where I can get a old style brown thermostatic valve screw in type for model number WL1500RC I’ve asked crosswater AND THEY SENT ME THE WRONG ONE 🙈 but insist it isn’t part number SC50-t20 It doesn’t screw in and has a funny o ring on a 45 degree angle Many thanks
  12. BENNEJ0

    ideal standard dual flush valve problem

    i have 3 sottini toilets with a compact cistern. It has an ideal standard dual flush mechanism. 2" entry The ideal standard is poor quality in my opinion, I have replaced the washer and complete unit several times but it always leaks within a short time (between 0-18 months), I would like to...
  13. E

    Lockshield valve removing cap

    Bathroom towel rail with straight lockshield valves as in picture. Can't remove the top to tighten gland nut as it is leaking. Must be possible to remove but I can't and don't want to force it off.
  14. K

    Testing concealed shower valve

    Hi all I've finished running the copper for my concealed shower valve and tested both inlets and the outlet with cold mains (full pressure). I just wanted to ask is it considered necessary to test the hot inlet with hot water, or will the cold suffice? Many thanks P
  15. R

    microbore valve connection

    Hi all, just removed a radiator while decorating. One side was easy, the other just spun round and is now leaking. Have drained down system but not sure how to fix leak (not seen this connector before) ps was really tight - split the olive? The whole connector is spinning round. Thanks in advance.
  16. T

    Double Check Valve with isolator?

    Does anyone know where I can get a DCV with an isolator that is WRAS approved? I need one for an outside tap and have limited space so I could do with a combined item thank you :)
  17. T

    Filling Loop Double Check Valve

    I’ve noticed on my old Bosch boiler the DCV on the filling loop is fitted to the boiler side of the water supply. And there is no isolator valve fitted. The only thing stopping it from leaking is the DCV? IS this ok?
  18. L

    Megaflo auto air valve leaking again

    Hi, I noticed some months ago that my Megaflo auto air valve was leaking so I replaced it, the replacement valve has also started to leak with a waxy residue. I recall that the original AAV had a black lid and the replacement has a brass lid, does it matter which version is fitted? Can I...
  19. B

    How do I replace a double-check/non-return valve?

    I need to replace the double-check/non-return valve on the pipe that goes out to the back garden tap under the sink. I got the correct replacement part, but I am not sure actually how to remove the original non-return valve on the pipe. When I loosen the two nuts, it can slide a bit back and...
  20. S

    morco gb24 seies 11 diverter valve

    hi ned to service a morco gb24 diverter valve in my sons static the valve is passing so when you use the water it creaps down the flow and return so the responce time is slow on water demand morco are very help full wonder if aybody on here has come across this problem and wanted to know if some...
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