What is this?

[MichaelC]

Can someone please identify the attachment at the top
of the cold water pipe just prior to it entering the heater?

Thank you

 

[JoeD]

It's a vacuum breaker. Prevents water from siphoning back in the main water supply in the event the main water is shut off. The line to the right probably goes to an outside hose bib. That is where they normally install the breakers.

 

[MichaelC]

With the shut-off valve right where it is do I need the breaker as well,
assuming I close it before I shut off the main.

I ask because i'm re fitting

 

[JoeD]

I don't have them in my home. It could be a code requirement for your region.

 

[CallMeVilla]

We call them anti-siphon valves. More typically, they are found on landscape valves to prevent yard water from siphoning back into the house supply. They are required by code for that purpose. Otherwise, our exterior hose bibs do not require an anti-siphon valve -- but you area might have a different code.

It is usually best to assume that if you have such a valve, it IS required by local code. Keep it and work around it.

You are "re-fitting" what? Changing the hose bib? Just shut off the main and change out the bib, leaving the valve in place. Changing the water heater? Leave the valve and change out the connection to the heater.