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Velocity Noise

The radiant heating for my recent 375 square foot addition is fed by a 3/4-inch pipe with a Taco 008F6 (16-feet head/14GPM). I hear the hum in every room that the pipes pass along and after reading Dan's book, I now understand that this must be velocity noise.

When the heat was first installed, it had a smaller taco circulator but the room did not receive adequate heat, (Staple up underneath 3/4 plywood and 3/4 hardwood with no reflectors) so the plumber increased the circulator size.

Right now, the water temp is 145 degrees to maintain heat on design days. Am I simply stuck with this, or is there some solution the noise, which isn't terrible, but I would like the quiet. Heat loss for the room is aroun 12,000 BTU.

Do I just live with it?



  • how long were the loops, out of curiousity?
  • don_70
    don_70 Member Posts: 3
    Not long enough

    Thats just plain crazy,to have that much circ on that small
    of a distribution system.

    You could have a thousand feet of 1/2 pex and still not need that much pump.

    You know with force air we call it jet noise,I guess with water its called train noise.

  • Steve Garson
    Steve Garson Member Posts: 191

    I am guessing that there are four loops each of around 125 feet connected to a manifold at the addition. This is connected to around 40 feet of 3/4 to the boiler.
  • S Davis
    S Davis Member Posts: 491

    This is what I come up with on the HDS software.

    S Davis

    Apex Radiant Heating
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928

    No chance of increasing your supply temp? If you're actually moving 14 gpm, your delta-t is absurdely low--less than 2°. Higher supply temp and MUCH lower circulation rate should still give the output you need.
  • J.C.A._3
    J.C.A._3 Member Posts: 2,981
    How about a ,

    Grundfos up15-58 3 speed pump? When you need the flow for design days, just flip the pump speed up a notch and when you can get enough heat from the floor when it's a bit milder out side, you can turn it down.

    The flow chart for it covers a whole lot of different pumps, but I still wonder why it wasn't figured out first.

    Second question. How are the pipes going out to the manifold secured? Tightly to the beams isn't my first choice. Chris
  • Steve Garson
    Steve Garson Member Posts: 191

    Multi-speed pump is a good idea. Yes, I can raise the water temp, the question is at what point to I reach design limits on the heating tubes. The copper pipes are fastened to the floor joists and well insulated. There is a 20*+ temperaure drop between input and output.
  • Alex Giacomuzzi
    Alex Giacomuzzi Member Posts: 81
    Something Appears Wrong...

    If you have a 20 degree delta T between supply and return, you are inputing 10,000 BTUH for every gallon flowing. If you were infact flowing 14 gallons, you would be putting in 140,000 BTUH. Your numbers indicate 30 BTUH per S.F.
    This appears reasonable. This could be achieved by 1.2 gallons flowing......... now problem for 3/4" copper nor the pex..

    Tell us about the insulation below the tubing. What thickness, what type etc. The heat maybe going somewhere, and it might not be going where you want it.

    Any other information you have to share??
    Good Luck........ Alex
  • Steve Garson
    Steve Garson Member Posts: 191

    The tubing is stapled to the underlayment. There is a 2-inch space with foil faced 1/4-inch bubble insulation with six-inches of fiberglass batting. The joists have firring strips with 3/4-inch foam board between them, all faced with 5/8-inch blue-board and plaster. An unheated garage is below.
  • m_3
    m_3 Member Posts: 19

    Steve, what kind of tubing are we talking about? Is a flexibe plastic or rubber? Or are the copper tubes you mentioned what is attached under your floor? If hard copper tubing was used, what you are hearing might be vibrations, and not water noise?
  • Steve Garson
    Steve Garson Member Posts: 191

    The tubing stapled up to the floor is black rubber radiant hose. The sound I hear is from the copper pipes.
  • Gordy
    Gordy Member Posts: 9,514

    Steve, Living spaces over unconditioned garages makes life difficult, so do cantilevering second floors. Did you notice the noise with the taco 007? If not I would try going back to this pump, and condition the garage area with a temporary ready heater to say 40-50 degrees, and see if this helps your radiant better handle the space above with lower velocity.

    Alex is on the right track in trying to help you find where the heat may be going. Sounds like the insulation was done right Did you insulate the ends of the joist bays? big losses there. One other question I would have is what are your floor coverings in the areas?
  • Steve Garson
    Steve Garson Member Posts: 191

    I just reviewed my gas usage for this last year for this space: 314 therms for this heating season; with 4373 degree days. With 12,000 BTU heat loss. My guess is that the plumber who did the work did not take into aacount how the king size bed and 8x10 oriental rug would block the heat transmission.
  • jeff_51
    jeff_51 Member Posts: 545
    you may have something there

    If the bed is on a solid frame, you may have to put it on a hollywood style frame, that gets everything off the floor and if it is a good quality wool rug, that is a great insulator.
  • Joe Mattiello
    Joe Mattiello Member Posts: 622
    1.2 gpm is al that's required.

    You can do that with a Taco 005. I'm not sure why the technician was thinking of using a high head circulator like the 008. Most people use the Taco 007, because it is more readily available.

    Taco, Inc.
    Joe Mattiello
    Technical Service Technician
    [email protected]
    401-942-8000 X 484
    Joe Mattiello
    N. E. Regional Manger, Commercial Products
    Taco Comfort Solutions
This discussion has been closed.