Water Hammer coming through auto feed valve?

Discussion in 'HVAC Heating & Cooling' started by MarkB, May 3, 2008.

  1. MarkB

    MarkB New Member

    Messages:
    8
    Thanks in advance for the help...I've checked posts for this one but it seems unique because it involves both domestic water as well as my heating water. I'll attach a photo of the system.
    When water is shut off anywhere in the house a loud banging is heard with what sounds like an echo. It also seems to happen when the furnace completes a water heating cycle. It seems to be coming from a furnace component. When I use the quick fill on the auto feed valve I hear the banging from somewhere within the components pictured. If I shut off the water supply valve to the auto feed the banging is still heard when water is used in the house. The banging no longer occurs when I close off the RETURN ball valve...it seems to solve all of the problem noises. I obviously can't keep the return to the furnace off. Could it be water pressure (hammer) flowing through the feed valve into the furnace system...the check valve located near the air scoop (due to the echo of the bang) or...???
    Triangle tube Solo 110 condensing boiler with a smart 40 indirect water heater. There is an expansion tank attached to the air scoop (not pictured).
    Pressure is usually at about 15 PSI.

    Attached Files:

  2. krow

    krow Plumber

    Messages:
    906
    Location:
    Ontario, Canada
    It really sounds like you may have an expasion issue, or your circ. pump is not pushing the water fast enough out of your heater
  3. MarkB

    MarkB New Member

    Messages:
    8
    Thanks krow. I did suspect an expansion issue...this morning I quickly shut of the supply valve (above the pump pictured) while the furnace was heating the house and I got the same bang...Any ideas or should I call someone in to evaluate?
  4. krow

    krow Plumber

    Messages:
    906
    Location:
    Ontario, Canada
    You should have a way to control when the circ pump kicks in. (it depends on how it is wired) .

    If the pump has a delay before it turns on (usually a temperature setting on the low limit switch), you may want to lower the temp setting 10-20 degrees, this way the pump kicks in earlier. The idea is to get the hot water out of the boiler before it gets too hot.

    ' That may cushion the banging
  5. MarkB

    MarkB New Member

    Messages:
    8
    Hmmm...ok I can do that...it makes sense for the banging when the DHW heating shuts down... but the banging from water use/shut off throughout the house happens weather or not the furnace is hot or cold, or on or off for that matter.
  6. krow

    krow Plumber

    Messages:
    906
    Location:
    Ontario, Canada
    Are you suggesting that you have 2 sets of banging? 1 is not related to the other.

    In this particular case, you can purchase 2 air chambers from HD or your local plumbing supplier and install them as close as possible to the faucet that is the noisiest. (I suspect that you have a faucet that shuts off really quickly). Install 1 on the hot line and 1 on the cold line (maybe underneath your cabinetry. ie: kitchen cabinet near sink)
  7. MarkB

    MarkB New Member

    Messages:
    8
    Yah...any water that is used in the house causes this banging in the furnace components...when I close the main return valve on the furnace I get no banging from any source be it water used in the house or use of the furnace. The only connection between the domestic water and the furnace is the auto feed valve.
    Check out my original post...I suspect the shock is going through the feed valve into maybe a check valve thats banging???
    Thanks again...strange one eh?
  8. krow

    krow Plumber

    Messages:
    906
    Location:
    Ontario, Canada
    I looked at your photo again. Can you point to where you feel it may be coming from?

    I still think you have 2 different issues, I just want to varify
  9. MarkB

    MarkB New Member

    Messages:
    8
    The Valve in Blue is the Return which if I shut off I hear no noise from anything. In Red is the check valve which is the closest area I can figure the bang comes from. If I get someone to use water anywhere in the house I hear it from this area on the piping. (I have bled that check valve and found no air)
    I thought it was 2 issues as well but I'm not so sure. Last week I put 2 water hammer arrestors in my 1/2" water lines...no difference. Then I discovered the return valve senario.
    Thanks again for your time!

    Attached Files:

  10. krow

    krow Plumber

    Messages:
    906
    Location:
    Ontario, Canada
    From where I sit, (the red circle) it looks like a swing check valve. If it is, thats where its coming from. The brass disk is opening and closing in a brass housing (metal on metal) as you are using water/heat. You use hot water, and your boiler comes on,/ flows,/ stops heating ,/ pump shuts down,/ check valve closes (bang , bang noise).

    Am I with you so far. Replacing that check valve with a different type might be the only thing that you may need.

    Fill me in with anything else you are noticing, no matter how small it may be, when you hear the banging
  11. MarkB

    MarkB New Member

    Messages:
    8
    The only other thing I can think of is it happens weather we use domestic hot or cold water. Could the water pressure be going into the feed device and continuing on to the check valve? the noise occurs even if I shut the ball valve to the auto feeder. It doesn't occur when I shut the Return valve to the boiler. (which I guess is leaving the check valve with no flow to open.
    What type of check valve would you recommend...or I could try it with just a nipple and no valve to see if it does the trick.
    I'm also going to check the water pressure coming into the house.
  12. krow

    krow Plumber

    Messages:
    906
    Location:
    Ontario, Canada
    The noise is still happening after you shut off the auto feed because your circ pump is still running or moving the water.

    On the top of the check valve there should be a removable nut. Shut your systems down (water sources and electrical to the units) and remove the nut. The swing disk can be removed for cleanig and you can test that theory by placing the cap back without the disk and see if the banging still occurs.

    As far as a diff check valve, I'm going to have to get back to you on that.
  13. cattledog

    cattledog New Member

    Messages:
    42
    Location:
    Portland, Oregon
    Mark--

    Here's a few thoughts on your water hammer.

    First, let's look at the cold water feed to the boiler loop. You wrote: "I suspect the shock is going through the feed valve into maybe a check valve thats banging???" I under stand that when the ball valve before the auto fill is closed, the banging persists. Either that ball valve is defective or, it would appear that we can eliminate the cold water feed side. The closing of the valve before the auto feeder should isolate the heating loop from the domestic water system.

    Lets look at the heating loop itself. You said that when you close the return valve, i.e. break the loop, the banging goes away. So, the question is how can changes in domestic water pressure communicate to the heating loop when the valve before the feeder is closed?

    One place where the domestic water and heating loop interact is in the indirect water heater. I don't know whether you have a tank in tank heater or interior heating coils. Can you isolate the boiler dhw feed to and from the hot water heater from the floor/radiator heating loop and see if the noise goes away?

    There is a possibility that pressure changes in the hot water tank are communicating back to the boiler. There may be some sort of leak between the two systems, or there may be a need for pressure relief through an expansion tank on the domestic hot water system if there is some unexpected compliance in the tank shell.
  14. MarkB

    MarkB New Member

    Messages:
    8
    Hello again...sorry for the delay.
    The installer came by and suggested putting a small expansion tank on the heating loop of the indirect water heater (it's a tank within a tank design).
    I am going to remove the swing valve through the cleanout nut just to test it out as well...2 fairly simple ideas...hopefully it will clear things up. I'll keep you informed.
    Thanks!...Mark
  15. cattledog

    cattledog New Member

    Messages:
    42
    Location:
    Portland, Oregon
    Mark--

    If you are piped like the Prestige manual indicates, the hot water tank loop and the heating loop should be tied at the returns, and there is often a check valve on the inlet to the hot water tank. If there is a check valve in the system such that the hot water tank loops can not see the system expansion tank from the return side, it is effectively isolated.

    Isolation from the system expansion tank could give pressure spikes in the hot water tank loop, but the question now becomes, how does the use of domestic hot or cold water communicate back to the shell of the tank, and how do the pressure spikes create the banging noise.
  16. MarkB

    MarkB New Member

    Messages:
    8
    Hi cattledog
    The hot water tank loop and the heating tank loop do tie in together at the return. I don't see a check valve anywhere in the hot water tank loop. There is a circ pump but with no check valve installed.
    With the ball valve fo the auto feed closed the only place domestic water use can influence the system is through 1-the hot water outlet on the tank and 2 the cold water inlet on the tank. The pressure spike must be transfering from the inner tank to the outer one and into the heating system. Maybe the pressure is pulling the swing disk in the return check valve. The banging is followed by an echo...BANG,Bang, bang. which is why I thought it may be that check valve.
  17. anna_student

    anna_student New Member

    Messages:
    3
    Simple question

    A silly question. I just got installed a brand new hot water heating system in my house. I used your picture to ask the question. Could you tell me what is the device that I circled in green. I know the other valves, etc, but forgot to ask my plumber what is this thing doing. Greatly appreciated. Thanks.

    Attached Files:

  18. Furd

    Furd Engineer

    Messages:
    446
    Location:
    Wet side of Washington State
    Your "thing circled in green" is a pressure reducing valve that reduces the pressure of the domestic water to about 12 psi to fill the heating system.
  19. anna_student

    anna_student New Member

    Messages:
    3
    Where in this picture is the auto fill valve that MarkB mentions in one of his posts? What I am trying to work out is whether I have an auto fill valve in my system. In my old steam system it was obvious what part was responsible for automatically adding water to the system. I am not familiar with the hot water heating systems.

    What would happen if the pressure in my system dropped. Would the system automatically draw water from the domestic water circuit via pressure reducing valve. My ball valve to the pressure reducing valve is open just like in the MarkB's picture. Thank you.
    Last edited: May 18, 2008
  20. Furd

    Furd Engineer

    Messages:
    446
    Location:
    Wet side of Washington State
    The pressure reducing valve is often called the auto fill valve.
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