What's a non-return valve?

Factual Questions
1

What’s a non-return valve? I came across a reference to it, but don’t understand what it means.

2

What’s the context? There are any number of systems that could have a device with that name.

3

Could they be referring to a backflow preventer, which is used to seal potable water supply from say utility water in a industrial plant? If I remember correctly from my piping design days they were shown as a double check valve on a flow chart.

4

Broadly, a device that allows flow one way but not the other.

5

My first thought (without knowing the context) is that it sounds like a backflow-prevention valve. Outdoor sprinkler systems typically have a valve that only lets water flow one way, to make sure that water from outside (which might be contaminated with who-knows-what) doesn’t get pushed into the sprinkler head and back up into the house’s water pipes. I suppose that you might call this one-way valve a “non-return valve.”

If that’s not it, then I have no clue.

6

They’re also used in the feed to hydronic boilers and fire sprinkler systems to keep the potable water system free of contamination.

7

Piping, of course. :slight_smile: The valve goes in your blowpipe so that the bag doesn’t loose pressure when you take a breath.

From here

So it means a one-way valve? That’s what I’ve always called it. Just didn’t recognize the “non-return” phrase.

Thanks, all.

8

And, I love the Dope. Four useful answers in 20 minutes or less, or your money back! :slight_smile:

9

Not to mention in your veins, to prevent blood from flowing back towards your tissues and keep it moving towards your heart.

http://www.jobst-usa.com/veinsandvalves.html

Make that five useful answers. :stuck_out_tongue:

10

Also called a check valve.

11

So it’s a fluidic diode. :slight_smile:

12

…and use of several, as, perhaps an extinguishing device, would wreck da fire (or is that reaching a bit too much, even for me?)