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    armstroa's Avatar
    armstroa Posts: 1, Reputation: 1
    New Member

    Feb 9, 2009, 08:56 PM
    Water pipes knocking on upper floor, after pipes burst
    Hi - recently, my water pipes froze and burst, flooding my basement. I've had the pipes repaired.

    Now, when I turn on the hot water in my upstairs (2nd floor) sink, there's a knocking/clunking after I turn the hot water off. Its only the hot water (doesn't do it with cold water).

    When I turn the hot water off, the knocking is faster, and it occurs in more than one place in the bathroom, but it slows down. (so, its: knock-knock-knock... knock... knock... knock, etc).

    Would this be water hammer? Its not super loud. I'm just a little worried that some damage has been done upstairs because of the frozen pipes. There's no indication of additional water damage in the house beyond what's clearly because of the burst pipes.

    Any ideas?
    KISS's Avatar
    KISS Posts: 12,510, Reputation: 839
    Uber Member

    Feb 9, 2009, 10:57 PM

    There is generally 2 mechanisms:

    1: A faulty washer - usually this happens at a certain % of full flow
    2: Water hammer - is caused when water in turned off abruptly AND the pipes are not secure. Water hammer arresters can be installed at that sink.
    Milo Dolezal's Avatar
    Milo Dolezal Posts: 7,190, Reputation: 523
    Plumbing Expert

    Feb 9, 2009, 11:46 PM

    I think what you hear is how pipes are expending and contracting while hot water travels through the system. This will not be so audible, if at all, in summer time.
    speedball1's Avatar
    speedball1 Posts: 29,301, Reputation: 1939
    Eternal Plumber

    Feb 10, 2009, 06:38 AM
    When I turn the hot water off, the knocking is faster, and it occurs in more than one place in the bathroom, but it slows down. (so, its: knock-knock-knock... knock... knock... knock, etc).
    I like Milos answer. Knocking, popping, creaking and crackling pipes are a common complaint, especially in colder weather. I can tell you what's happening and take the mystery out of it but you're not going to like the repair. When a draw is made on a hot water line the line expands against a pipe strap next to a stud and when you drain hot water from your tub or shower it goes into a chase that is a little cooler then room temperature. The heat expands the pipe causing it to rub against the stud to which it is pipe strapped. This is the sound you hear. As it cools it contracts and the noise is heard again. To repair it you must tear open the walls and locate the pipe strap that's causing the problem and shim it tight. Most people when they learn what causes it just elect to live with it. Good luck and thank you for rating my answer. Tom
    olde_griz's Avatar
    olde_griz Posts: 1, Reputation: 1
    New Member

    Mar 26, 2010, 11:45 PM
    How to Fix Knocking Water Pipes.. turn off the main water coming intomyour house. Open all water outlets till they no longer flow with water. Including outside spigots. Then turn them all back to the off position. Then simply turn your water supple back on a little bit, no need to turn it on full blast. Water pipes have built in air compression areas that prevent the slamming of water into your pipes more then they can handle. When you turn your water back on very slowly? The air compression areas are generally restored. Thus eliminating your knocking pipes.
    speedball1's Avatar
    speedball1 Posts: 29,301, Reputation: 1939
    Eternal Plumber

    Mar 27, 2010, 05:44 AM

    Griz, you are responding to a year old thread that's dead. Please look in the upper left hand corner for the date. Besides that's not how you recharge the art chambers. Thanks, Tom
    CHayn's Avatar
    CHayn Posts: 177, Reputation: 10
    Junior Member

    Mar 27, 2010, 05:55 AM

    Help me out here, Speedie. Other than Griz not mentioning to let water drain through the lowest fixture, which would happen with all outlets open as he does mention, this is how I have been made to understand to recharge air chambers. The vacuum caused by draining your pipes would surely bring in the air needed, would it not? If you have a more effective method, I would greatly appreciate your help.
    I have had a service call before where the people were on a closed water system,(backflow preventer at the meter), and their expansion tank at the water heater had become waterlogged because their bladder had burst. They had the same symptoms as armstroa. If he has a closed system he may want to check his expansion tank. All of these suggestions are possible causes of his knocking and now a list of troubleshooting is available.
    speedball1's Avatar
    speedball1 Posts: 29,301, Reputation: 1939
    Eternal Plumber

    Mar 27, 2010, 09:15 AM

    Chaym, ( do you have a first name?)
    Recharging the air chambers will work the same on a system wit or without a backflow preventer.
    Shutting off the water and opening up the uppermost faucet and draining from the lowest would drain rge system but not all the condensate in the air chambers.
    The reason being that air chambers have no air flow to relieve the vacuum.
    I recharge air chamber like this.
    Back in the 60's we were required to to put air chambers on all bath lavatories and kitchen sinks. Over time water and condensate built up in them and they must be recharged. First turn off the house at the main house shut off valve. Then open hot and cold faucets at the farthest bathroom to prevent air lock.(This is important.)and drain the system from the lowest faucet. You will find under each fixture little brass or chrome valves. These are called angle stops. With a small pail held under the angle stop to catch the run off look under the handle of the stop and you will see a nut with the stem running through it. This is called the bonnet packing nut. Put your wrench on it and back it off counterclockwise. Now open the stop and remove the stem and washer assembly, The stop will began to drain. When it has quit draining reassemble the stop and move on to the next one. Do this on each one of your angle stops. There will be six of them in a two bath home. When you are done, close off the faucets you have opened, turn on the water to the house,
    After I've drained the system I can always drain more out of each air chamber. However, if simply draining the system works for you then it's your call. Hope I've explained it to your satifaction. :cool: Have a great week end, Tom

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