What is the common check valve size?

[zoov]

Hi, I'm looking at installing check valve after the water main (this is to reduce our prevent from pipe knocking)  - Can any one let me know what is the size of the check valve for common household pipe that I should buy?

I check the Bunnings website, looks like it has multiple sizes from inches or cm.

I live in Melbourne. Hopefully someone can help.  Thanks 

[MitchellMc]

Hi @zoov,

Internal water piping in your home is normally 13mm, which is 1/2inch.

You'd need to locate the waterline and measure it at the point at which you want to install the device to determine the correct check valve size. Be advised that a check valve simply allows water to run only in one direction, and I haven't heard of them being used to resolve pipe knocking (water hammer). Typically, to resolve water hammer, you'd install a hammer arrestor. As with check valves, these are generally designed for localised areas within a home and not something you'd put directly after the water main. The addition of these devices is considered plumbing work, so you'd need to employ the services of a qualified plumber to install them.

Do you experience water hammer in the entire house or only in a localised area, such as when you turn a specific tap on? Has this issue only become prevalent after your water was turned off for some reason? Occasionally, air can get trapped in the lines, which needs to be bled out by opening all taps in the house and then closing them off again, starting from the furthest point away from the mains.

Please let me know if you have any questions.

Mitchell

[zoov]

Thanks Mitchell. 

That's very informative.

I think I have one installed (the plumber called it pressure reducer? Or this is entirely different thing? Looks similar to the link).

But it didn't reduce any of the sound. Hence I was thinking about the check valve. 

The sound is probably coming around 4 or 5 devices (toilet basin , kitchen, laundry and bathtub). Some is louder than others. 

We feel the sound is more pronounced after we renovate the kitchen (but we did continue using the water though).

So I don't think due to air trapped inside the pipes? 

Any info would really help and appreciated. Thanks

[MitchellMc]

A pressure reducer is something different once again, but if it looks like the hammer arrestor then this could be a case of the plumbing using different names, @zoov. It might help with the water hammer, but that's not its primary role, unlike the hammer arrester. Water hammer is effectively shock waves of water running through your pipes. The hammer arrestor is a small section of pipe with a spring inside it that helps absorb this shock wave, dampening its force and reducing the noise. Typically, if this is a whole house problem you'd need multiple arrestors on most waterlines.

Mitchell