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Mixing valve and check valves

tomocartomocar Member Posts: 1
Former owner had a dog wash tub installed in garage (nice!) but there is a loud rattling sound emanating from this wall whenever the lawn sprinkler system (which is down-stream on the cold side) comes on.  I opened up the wall and see that there are check valves on both the hot and cold ahead of the mixer valve, and I'm pretty sure it is the cold-side check valve that is causing the vibration. (The tee-off going to the sprinkler is between the check valve and the mixer valve.)

1. Does this make sense?

2. Is it okay if I just take out the cold-side check valve?

3. Or if it is required, do you think it would help to move the tee to upstream of the check valve?

Thanks for any advice you can give me!



  • Jamie HallJamie Hall Member Posts: 6,693
    It makes a certain amount of sense but...

    it could also be the mixing valve trying to backflow.  It's happened.

    On whether it's required.  I don't know what code you are working with, but the code which I used to work with and enforce, when I did such things, required a reduced pressure zone backflow preventer between any domestic supply and an irrigation system.  Further, if the doggy wash does not have an air gap from the fill, or if there is a hose and spray attachement, it would require an RPZ on both the hot and cold lines.

    Even if it isn't code where you are, in my humble opinion it's a very very good idea.  A check valve does NOT qualify as adequate protection.

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-McClain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • KakashiKakashi Member Posts: 88
    rubber grommets

    if you can find out where the sound is coming from see if you can get a rubber grommet pipe clamp. Best to be safe in my book. If you can't find out exactly is making the noise, you can add some sort of expansion tank.

    Post a pic of the check valve if you can.
  • icesailoricesailor Member Posts: 7,265
    Mixing Valves/Checks:

    Code issues aside, the check valves are needed on the doggie bath shower because (I'm sure that) there is a hose with a shut-off nozzle spray to wash the pooch. You can wash kitty there too if you're brave and careful. You have to "scruff up" the cat. Grab the by the back/scruff of the neck like Momma cat does to move her babies. It puts cats right into a trance.

    If you don't have the checks, and you leave the valve on with the hose nozzle off, you get a cross connection between hot and cold. As long as the hose isn't long enough to get into the tub below the overflow rim of the tub, it is supposed to be legal. If not, they make inexpensive screw on back flow devices that go on sill cocks as an add on you can use. It is similar to each and every pull out kitchen faucet spray head that also acts as a spout. If the hose is long enough to get to the ground or be submerged in water, it needs to be protected.

    As far as the location of the cold water tee and the check valve, it should be moved to the house side of the cold water inlet, BEFORE the check valve. The hose outside needs to be protected too. For your own safety.
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