Quick question about service valve flow direction.

Why do service valves (15mm and 22mm) have an arrow indicating direction of flow?

Reply to
Rednadnerb
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Because the pressure in the direction of flow tends to help them seal. It is the same with most valves but not all.

Reply to
Bob Minchin

To seal what? there is a compression joint at each end and a ball valve in the middle.

Reply to
Rednadnerb

To prevent water passing through the valve when it is in the "off" position.

Reply to
harry

Not long ago I asked the same question on here and was given the answer, although I have forgotten who told me. Being curious I tested it, on a couple of good quality (Pegler) 15mm, not full bore, ball valves. In practice, with 2 bar pressure on the side away from the arrow they don't leak With 2 bar on the side with the arrow point they leak quite briskly. If you look into the ends the plastic seal is squeezed firmly between the ball and the machined and polished fitting at the arrow point side, while on the opposite side there is a wide space closed by some sort of clip where the ball and seal are inserted. So pressure from the opposite side to he arrow head forces the seal and ball closed, while in the other direction it tends to depressurise it and pull the seal away from the housing.

(Neither would seem to affect leaking from the spindle seal, which is how they generally fail in my experience, but maybe the better ones don't do this. I live in hope. I suspect this seal works if it is either used every day, or never used at all.)

Reply to
Roger Hayter

Thanks to all and especially Roger, that's the kind of detail I was looking for.

Reply to
Rednadnerb

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