What is this PVC pipe on my water main?

[Nick Evans]

I'm looking at adding a water softener to our home, but there's something on the line that I'm unfamiliar with.
Right after the main shutoff valve is a T with a PVC contraption above and attached.
What is it?
Trying to figure out if I should install before/after it, or cut it out... mostly just want to know what it is.

 

[hj]

It appears to be someone's misguided attempt to eliminate water hammer noises in the system.

 

[Sponsor]

 

[Nick Evans]

So nothing necessary to keep around.
Think I'll cut it out, during the softener install. Thanks

 

[Reach4]

City water?

 

[Nick Evans]

City water?

Yeah, city culinary water.