Auto wash water hammer

I am looking for a way to quiet my pipes.

During a house remodel "I" did a copper repipe. Spared no expense or effort.

I had the GC's plumber do the inspector mandated autowash drain line increase and tie into the laundry sink. During the process he had to move somethings around. To shift the washer box over an inch or so he cut the supply lines and put an elbow and street L to get them going down again, putting two 90s in the line above my hammer arresters.

Before I could get to it, the house was drywalled.

Could this be a reason for the loud pipes despite my hammer arresters? They are all strapped down.

Would it be of benefit to remove the two elbows and put in 45s to ease it? It will require cutting and taping drywall but will it save me from a life of loud pipes? Would it be worth putting hammer arresters in the 1" line in the attic directly above the laundry? That might be more of a pain.

Thanks.

noise

NOT being screwed directly into the pipe right above the valves has reduced their effectiveness. Changing the fittings will probably not have any effect on the sound. The hammer is occurring RIGHT AT the shut off valves so the arrestors should be as close to them as possible, and especially NOT in the attic.

The copper was soldered into the brass valves rather than threaded adapter. perfect fit.

They sell hammer arresters with hose adapters that I can screw onto the washers stubs. That would be the closest to the valves to get without putting them in the machine.

Hey, that would be a novel idea. Sell a washer with arresters installed in it.

There are also washing machine boxes with arrestors at the valves.
Oatey Eliminator

arrestors

Yeah, I looked for those but couldn't get one of those boxes when I needed it.

Would you think it is better to attach the arrestors at the box or to the washer?

If you have the ability to I think at the box is the best bet. Arrestors should be tie to the rigid piping, not the hose to/at the washer.