Water hammer. Replacing the Rough in valve in bathroom remodel

Discussion in 'Shower & Bathtub Forum & Blog' started by deadman9876, Oct 14, 2018.

  1. deadman9876

    deadman9876 New Member

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    I've been (slowly) remodeling our master bathroom due to age and water leak. I decided to replace rough in valve and move it higher as it will be a shower only now (roman tub before). The setup is pretty simple, however both hot and cold have capped off runs extending up the main lines. I believe these are for noise/vibration reduction. Most of the pictures and diagrams don't show these runs, so my question is do I need them? Is there something more modern that I should replace them with?

    [​IMG]

    Thank you,
    J
     

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    Last edited: Oct 14, 2018
  2. Reach4

    Reach4 Well-Known Member

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    These are water hammer arrestors. They can work if the water has much air in them, but otherwise expect the air in them to dissolve into the water. Instead today, captive air water hammer arrestors are used.
    [​IMG]
     
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  4. deadman9876

    deadman9876 New Member

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    Thank you so much for the info. From what I can tell I should replace these but lucky they are more compact these days and fairly easy to install. Thanks again for your help.
     
  5. Reach4

    Reach4 Well-Known Member

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    If you don't get water hammer, I would not replace. A washing machine has a quick-close valve. A tub or shower does not, so those are unlikely to have water hammer. I am not a plumber.
     
  6. Terry

    Terry Administrator Staff Member

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    The new shower valves are either pressure balanced or thermostatic. they are slow closing and now no longer need the hammer arrestors.
    I installed a lot of air chambers in the 70's for the old valve like yours. I haven't done that since codes switched to pressure balance or thermostatic.

    Git rid of the air chambers.
     
    Last edited: Oct 16, 2018
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    The vast majority of new shower valves don't need hammer arrestors. Those old ones have probably long since lost all of their air. If you're replacing the valve, double-check the installation instructions. IF they call for them, use them, but that will be rare.
     
  8. deadman9876

    deadman9876 New Member

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    Thanks so much for the help. I installed the new valve today and somehow broke the water heater. The hot pipe coming from the heater is hot to the touch however the water doesn't get more than lukewarm. I was wondering if it's because I don't have a cartridge installed in the new value (only the cap that it came with) and therefore the drop in pressure by turning on the hot causes the cold to flood the system. Does that seem possible?
     
  9. Reach4

    Reach4 Well-Known Member

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    Run the hot at the kitchen, and see if that water comes out hot.

    If it does, try the lavatory next.
     
  10. deadman9876

    deadman9876 New Member

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    All the faucets are lukewarm, yet the pipe on the heater is hot, thats what makes me think its mixing with the cold somewhere. Because the new valve doesn't have a cartridge (only the stopper) would the hot and cold be pushing against each other inside the valve, causing the cold to back into the hot lines when the hot is open?
     
    Last edited: Oct 16, 2018
  11. Reach4

    Reach4 Well-Known Member

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    Probably. Why don't you have a cartridge?

    Do you have any stop valves at the new valve? If so, shut them off, or put in the cartridge.
     
  12. deadman9876

    deadman9876 New Member

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    I didn't get a cartridge because it comes with the trim kit (Delta) and I haven't picked out the trim yet. I'll go get a cartridge and install it today and report back. Thanks for the help.
     
  13. Reach4

    Reach4 Well-Known Member

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    Last edited: Oct 16, 2018
  14. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    With just the cap on, the hot and cold can easily mix together. The hot path will take the path of least resistance, typically pulling some cold along with it, and vice-versa.

    The way around that is to have in-line shutoffs for the tub/shower valve, have the cartridge in, or install the plug to prevent it from crossing over. They used to come with the valves, but to save the $.10, they stopped on most of them.
     
  15. WorthFlorida

    WorthFlorida The wife is still training me.

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    With your home on a slab and no shut off access this is the type of Delta valve body to use with "stops". The stops allow water shut off at the valve body for any changing of the cartridge in the future. You want the cartridge installed so you can do a leak test. Turn on the water to purge most for the air out of the pipes, then cap off the shower pipe. Allow the water to remain on for a few days to be sure there are no leaks.

    I did a bath remodel and did not do this. Years later I found a leak in the wall from garage side of the shower. I had a bad sweat joint between two 45 degree elbows from the valve body to the shower head and of course it only leaked while using the shower. Fortunately, I used Dense Shield and had little mold and no wood rot. Only the garage drywall was bad which was an easy fix.
     

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    Last edited: Oct 18, 2018
  16. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Follow the instructions about purging the lines by letting them actually flow water a bit prior to installing the cartridge. You may have to get creative to keep water from going everywhere but it's worth it not getting any debris in the cartridge and possible the mating surface of the rough-in valve body. If it happens to be hard enough, it can score the parts, making it hard to impossible to create a good seal later on.
     
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