Advice on PEX system valve and hammer arrestor details

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by jono604, Nov 9, 2011.

  1. jono604

    jono604 New Member

    Joined:
    Nov 1, 2011
    Location:
    vancouver, BC
    Hello

    I have installed a new Trunk-and-branch PEX system as part of a bathroom remodel (3/4" trunk, 1/2" branches to supply the fixtures)
    It's a simple bathroom with, toilet, single sink, tub/shower (single mixer valve)

    I'd like some advice on a few things:

    1 - installing hammer arrestors in this system
    a) is it necessary?
    b) which fixture branches should get the hammer arrestor?

    2 - installing shut off valves on the branch supply lines to the shower mixer valve
    a) is it necessary? Is there any code requirement for this?

    any advice would be appreciated.
    thanks
    Jonathan
     
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    In a bathroom, most fixtures do not need hammer arrestors at all. Now, some shower valves specify them in the installation instructions, and if your valve does, then you should install them. You get the 'hammer' effect when quickly shutting water off, the inertia of the moving water then pushes the pipe and it bangs into something making noise. On most typical valves used in a bathroom, you usually can't turn them off fast enough to require a hammer arrestor. Some toilet flush valves shut off quickly, and one there might help, depending on the toilet you choose. Most don't need one.

    You do not require individual shutoffs for any of the lines, and especially on a shower, most plumbers would not look for one. If you want to put some in, fine, but it isn't required. You'd normally install one for the toilet and the vanity, though. While you can use a compression shutoff valve directly on pex if you get one with the internal reinforcment ring, it's better to stub it out to copper and anchor it in the wall so it has some regidity and you aren't flexing it when trying to open or close the valve.

    If the shower is also a tub, keep in mind you should NOT use pex on the outlet side of the valve, at least to the tub spout. If you do, you WILL have problems...it needs to be full bore ID of metal...pex's ID is quite a bit smaller than copper or brass.
     
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  4. jono604

    jono604 New Member

    Joined:
    Nov 1, 2011
    Location:
    vancouver, BC
    Thanks for the feedback Jiim

    I'll take a look at the fixture specs and see if any of them require a hammer arrestor.

    For my toilet and sink I'm planning to terminate in a copper stub-out elbow like you mentioned. I like the rigidity of this for the shutoff valves.

    Thanks for the advice on the valve outlets. I was planning to run copper to drop-ears for the tub spout, shower-head and hand-shower.

    Would you recommend using copper between the mixer valve and diverter? I'm using a three way diverter that directs the mixed water to one of the three tub/shower outlets.

    Would you supply the mixer directly with pex or would you use some type of copper connection?
    I was thinking of putting a PEX barb fitting on the inlets to the valve and going straight in with PEX. I would use some 90deg bend strain-reliefs on the tubing and strapping to the framing to avoid loading the fittings.

    thanks
    Jonathan
     
    Last edited by a moderator: Jan 28, 2014
  5. Tom Sawyer

    Tom Sawyer In the Trades

    Joined:
    Nov 29, 2010
    Location:
    Maine
    I have run into that several times in the past couple of years. It seems there are quite a few plumbers out there that have a problem reading the directions. Under the new IPC water hammer arrestors are no longer required.
     
  6. hj

    hj Moderator & Master Plumber Staff Member

    Joined:
    Aug 31, 2004
    Occupation:
    Plumber
    Location:
    Cave Creek, Arizona
    PEX usually has enough "flexibility" that it will absorb most "water hammer" effects. Unless the hammer arrestor is installed RIGHT AT the source of the hammer it will be ineffective. Most tub/shower valves are serviced without removing the trim plate so any "intergral stops" are never seen or used.
     
  7. ssimacdonad

    ssimacdonad New Member

    Joined:
    Jan 28, 2014
    Location:
    Alberta
    I had a problem with hammer originating from automatic washing machine water shut-off valves. The machine is late-model with electronic controls. I live in a condo with PEX piping and I have been extremely concerned that the hammer (i) will annoy my neighbours and (ii) might cause a line rupture somewhere in the system. So I purchased two hammer arresters made by LynCar for about $20 each (don't know if the brand really matters) and installed them at the wall valves in the laundry room. Some slight improvement but still noisy and worrisome. THEN I read this thread and noted that I should install them as close as possible to the source. So I moved them to the washing machine end of the (stainless steel braided) connection hoses. PRESTO!!!! quiet as a mouse! Thanks for your help!
     
  8. Thane

    Thane New Member

    Joined:
    Dec 9, 2015
    Location:
    Bellingham, Washington
    I have the same problem with a new washing machine. I used the the supply box with integral water hammer arrestors for both hot and cold but the hammer is noticable. How did the water hammer arrestor fit on to the stainless braided washer hose?
     
  9. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    Last edited: Dec 10, 2015
  10. Mike Garrod

    Mike Garrod Mike G

    Joined:
    Jun 9, 2015
    Occupation:
    Plumber
    Location:
    British Columbia
    Bumpers are typically only on your washing machines and dishwashers in homes. In BC it is code to have them on dishwashers if I'm not mistaken. I have had to put them in public washrooms as well on flush valve fixtures. And IMO, I would put integral stops on the shower valve. Often when a shower needs servicing it is the cartridge that needs to be replaced, and it is easiest just to pull the trim off, shut off integrals, service valve then turn integrals back on rather than shutting off the whole house and draining everything just to work on the shower. But that's just me
     
  11. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    The arrestors come in lots of different configurations. They will last a long time. THey will likely fail eventually, so you will want to put them where you'll have access later on.
     
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