"hammer arrestors" on tub/shower mixing valve & a question about PP 0x8 valves

[ndog]

I'm considering updating my bath/shower fixtures as the wall is open and they're looking dated. Right now I've got the standard moen clear acrylic knob pull to control flow and turn to adjust temperature; no pressure balancing or thermostatic balancing. Initially I looked at a pp set because it was all metal and heavy, everything but the cartridge is brass plus I like the design; something that a couple of the moen sets I looked at were not. The set includes a 0x8 valve and I've come across a thread here about these valves not having enough pressure or flow, is this a common complaint or just this one particular poster?

The second question is right now the copper supplies just come up from below and are connected to the inlets on the current valve with a 90' elbow and about an inch of pipe. I've seen on a couple home improvement shows bringing the supplies up to the level of the valve then using a tee with hammer arresters or just 6-8" of pipe with caps on the end on top. Is this something I want to do? The installation pdf of the faucet I'm considering doesn't mention doing this or not doing it. http://www.diyadvice.com/diy/plumbin...r-tub-faucets/ There's a picture here with the arrestors I found with google if my explanation isn't clear.

[hj]

The PP tub/shower valve is not one I usually install, but those that I have serviced do not seem to have that problem, nor do the customers mention it. I have not installed arrestors or air chambers in water systems in the 40 years I have been in this area.

[jadnashua]

A few people have mentioned that the installation instructions call for hammer arrestors. If yours don't, it's probably safe to not install any. If you decide to, forget an air chamber on a T, use a 'real' one that is engineered. It has a sealed chamber and either a bladder or a piston that separates the water from the trapped air.

[ndog]

Thanks, normally I buy moen or delta faucets but this particular PP model is exactly the look I'm going for and delta/moen do not have equivalent trim. If there's no reason not to use this valve then I'll keep the pp.

There's no mention of arrestors in the instruction booklet and all of the diagrams show supplies coming up and being connected with a 90' elbow--so I'll skip them too.