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Noisy hot water line

cwtaft | Posted in Construction Techniques on January 13, 2012 08:06am

I have a hot water line that makes a variety of popping noises when it warms up as hot water begins flowing through it.  The hot water heater is on one end of my house and the bedrooms are on the other end.  The line is a 3/4″ copper line with foam insulation that runs through 2×4 floor trusses (see attached photo).  It is lying on the bottom of the floor trusses and is anchored by copper straps on every other truss.  The line runs straight for about 35′ before it makes a right angle turn to go around a stairwell. 

It is clear the noise is caused by thermal expansion of the copper line.  It has made noise since we moved into our new house in 2008.  I thought that the noise would fix itself after a few months but that has not happened.  So I recently cut a few small holes in the downstairs ceiling to see if I could determine the exact cause.  The pops come from different locations along the line but the loudest ones seem to come from the end of the straight run which makes some sense since that is where the thermal expansion is the greatest.  I have inspected three of the copper straps so far and none seemed particularly tight.  However on some of the trusses the copper line was quite tightly pressed against the wood, I presume due to slight misalignment of the trusses.

I would like some suggestions on ways to eliminate or greatly reduce the popping.  So far I have placed a couple of old plastic gift cards with a thin coating of grease between the wood and the line and it seems to have helped some but has not eliminated the problem.  I suspect that the best way to fix the problem is to add a jog in the middle of the straight run which would take up a lot of the thermal expansion.  I would like to find an easier fix if possible.  I would also like to know how this line should have been installed to prevent this problem in the first place.   Thanks for your help.

 

Cyrus

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Replies

  1. calvin | Jan 15, 2012 10:35am | #1

    cyrus

    I agree with loosening the pipe straps, however I would cushion between the wood and lines with more than stiff cards.  Can you work some foam under there?

    Holes through plates seem to be a notorious place for the expansion to make noise.  If drilled too tight or with pipes temporarily held in place with shims prior to soldering constrict the slightest movement.

    Isolated (or insulated) from framing would have been the ticket in the beginning.

  2. jej | Jan 16, 2012 05:04pm | #2

    noise

    maybe you could try placing a tee in the line and installing a air hammer ,much like you would for a refer ,dishwasher or wsher .i would do the air hammer the same diamiter as the line .

  3. cwtaft | Jan 25, 2012 08:39pm | #3

    Noisy hot water line

    Thanks for both replies.  I have been busy cutting 4"x5" holes in my drywall basement ceiling to get access to the pipe straps.  I have loosened many straps and placed greased cards between the pipe and the wood and also put some grease around the pipe at the strap.  This has almost completely eliminated the noise on the main straight run of pipe.  I was still getting a little noise on a connected pipe running to the kitchen sink so I am cutting a couple more holes for that.  It looks like this fix will do the trick.  Now all I have to do is patch about 12 drywall holes.  Thanks for the help.

    Cyrus 

    1. calvin | Jan 26, 2012 07:23am | #4

      cyrus

      I'd go a bit further.  Playing cards have no cushion.  Can you fit something between that compresses ?

      1. DanH | Jan 26, 2012 08:10am | #5

        I don't think that a cushion is necessary.  It's a thermal creap problem, and simply providing a smooth, low friction surface is all that's needed.

        If water hammer were the problem then the solution would be exactly opposite -- anchor the pipe tightly but provide cushioning.

  4. cwtaft | Jan 30, 2012 10:36am | #6

    The only way I could get some cushioned material under the pipe would be to remove the copper straps completely.   The plastic cards with grease seem to have done the trick so I am now closing up the holes. 

    Cyrus

  5. Paladin51 | Feb 25, 2012 10:09am | #7

    Thermal Expansion (Creep) on Hot Water Pipes

    I have the same problem. My pipes pass through 2x12 floor joists & when the heat comes on the noise is unbearable. Shame on my HVAC guy for misalignment & not enough clearance around the pipe.

    The grease & card sounds like a good plan. Doesn't someone make some sort of a teflon (or other material) sleeve to insert into the hole to allow the pipe to slide on?

    JDH

    1. [email protected] | Feb 29, 2012 02:00pm | #8

      It is a UHMW plastic with an adhesive backing. 

      Quite a few of the woodworking stores have it for building jigs.  In industry you can use it to isolate dissimilar metals to prevent corrosion.  I first used it, and delrin pop rivets, to isolate stainless steel screen material from the steel support frame.   There had been a long term issue with the screen corroding at the rivets and falling off the frame.  The "slick tape", and delrin rivets provided an electric break bewteen the materials and ended the corrosion issues. 

      I did a Google search and found a bunch of sources.  Amazon has four different versions in Tools and Home Improvement. 

      1. DanH | Feb 29, 2012 07:46pm | #9

        I've used pieces of plastic cut from a thin roll-up cutting board (about 1/32" thick, I'd guess).  It's fairly slick, and hard enough to wear well.

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