Shower mixing valve piping

[Jayman]

During my remodel I uncovered the shower wall with the existing mixing valve. As you can see in the picture the line entering the valve on the right tee's off and jumps from 1/2 to 3/4" or 1" goes up about a foot and then is capped off. Is there a reason for this? My first thought was that the contractor didn't have a 1/2" elbow and then just stuck this in the arrangement?

 

[johnjh2o]

That is a hammer arrester. What I don't understand is why there isn't one on the hot.

 

[Jayman]

I am installing a modern thermostatic mixing valve to replace this one. Its an externally mounted mixer i.e. not in the wall. Would it be appropriate to install this way on both the hot and the cold? Thank you

 

[phishfood]

No, those field manufactured shock arrestors don't do any good after awhile. The air above the water is slowly absorbed into the pressurized water. If you want to install shock arrestors, buy the factory made ones with piston seals that have a gas charge in them.