Water Hammer Arrestor Placement & Size Question

[Bird Doo Head]

Hello All!
I installed a Grohe Grotherm 3-Function valve for shower, hand held and tub spout. It is push-on, push-off. There is noticeable water hammer when pushing any button to turn the valve off, even at a low flow setting. The pipe straps are Upnor talons, so the pipes are not rigidly held.

I don't explain things too well, so a drawing is attached.

Due to framing, I can't install an arrestor, even AA size, at the valve.

My questions are if it is OK to install them some distance from the valve. Ideally, I will install pre-made piston type arrestors horizontally.
I can also install tube-and-cap ones by using a 1/4 street bend at the tee and sending the tubing up, but it will be rather short, ending before the valve. It will also have to curve around a bit. I'll use PEX. (Green in the drawing)

In the drawing I show two options for placement. One is in the basement & will be very accessible for service later. The other is in the wet wall. Access there is possible, but tedious. (It's a pantry closet wall that is removable in about an hour.) I've never had a pre-made on, so I don't know how often they have to be changed.

Question Two:
I also find conflicts in the fixture unit charts for the valve and for what each arrestor can handle. Will size AA work for a shower valve?

Thank You Very Much for helping clear up my confusion.
Paul

 

[breplum]

The only worthy water hammer arrestors are factory assembled and cannot ever be serviced as far as charge (its nitrogen anyway).
Do not bother whatsoever with capped pipe pieces. The air is absorbed within weeks or months. It was a not tested idea and is completely deleted from codes.
Hydraulic shock noise is very hard to effectively tackle. I'd put nearer the valve initially and run it through tests before closing the wall.
Don't be surprised if commercial WH arresters hardly do anything.
I've been using them on quick closing Grohe volume controls and there is still insurmountable shock.

 

[Bird Doo Head]

Thank You Breplumb for the advice you gave.
Based on your experiences with Grohe valves, I won't be overly surprised if the arrestor doesn't solve the problem.
Thanks Again,
Paul