What is this brass thing ?

Hi, This thing shown in the picture connects the cold water supply from the wall and the washing machine valve. There is a thin copper tube from its bottom and goes into the wall. There was water dripping sound started couples of weeks ago. We got a handyman came over to check. He open the cap on the top and there was a rectangular rubber block with a vertical pin attached inside this thing but he has no idea what it was.

Any idea what this thing is and how to stop the dripping. I think perhaps this rubber block must have worn out and cause the dripping but I have a hard time finding what is this thing called.

Tks...

My guess (i'm an architect, not a plumber...) is that it's a trap primer. Do you have a trap under the washing machine that always has water in it? It is supposed to drip, but only when the washing machine valve closes, and only a small amount. The hole on the bottom portion is likely an air break.

I believe Calvin )) is right.
Here is a JR Smith trap primer.

Tp

That model trap primer drains water continually when water flows through the line it is attached to. But if it leaks when there is no flow it is worn out, and the easiest thing is to replace it with a new one of the same model to make replacement easier.

So.... does that put an architect above a handyman? ha ha ha!

Spaceman Spiff said:

So.... does that put an architect above a handyman? ha ha ha!

Click to expand...

As an employee of a consulting engineer, I would say yes, in this case anyway.

thanks all

Thanks for all of your valuable information. At least I know now it is called a trap primer. The dripping is getting heavier these few days but I couldnt see any significant movement of the indicator in my water meter.