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Noisy baseboards/piping

dbsoccer Member Posts: 5
edited February 12 in THE MAIN WALL
Occasionally I can hear the flow of water in the pipes of my hotwater heating system. I have a 86 vintage Burham boiler with Slantfin baseboard. All the pumbing is copper. I have roughly 8 zones. Until just recently things were quiet but lately I can hear noise once in awhile. It is so infrequent that I have not confirmed that I have noise in all zones. I just checked the system pressure and with the system heating and the pump running it was about 20psi. After the boiler stopped firing the pressure approached 30psi. The bleeder/vent valve on the air scoop is fairly new (5 years old or so) and it does not appear that any water or corrosion has been oozing out from under the cap.

As I installed the system some 35 years ago and have maintained the system as well, I'm pretty familiar with the systems, the parts and how the pieces work together. I could try purging the system (I've done that several times over the years) but I don't know why that would be required if the system has been working fine and only recently started making noise.

Any insight anyone could provide would be very much appreciated.



  • mattmia2
    mattmia2 Member Posts: 3,177
    What is the pressure in the expansion tank with no pressure on the system? Does water come out of the schrader?
  • dbsoccer
    dbsoccer Member Posts: 5

    During my last project involving the boiler I installed a Watts RBFF. This will make checking the expansion tank pressure easier. I am assuming you are referring to the schrader valve on the expansion tank thinking that I may have a ruptured bladder in the tank.
  • dbsoccer
    dbsoccer Member Posts: 5
    Based on Mattmia2's questions I have concluded that I have been negligent with my boiler maintenance. The expansion tank is relatively new but I have neglected to check its pressure since installing it several years ago. I suspect that the bladder is fine but the pressure is way down. And with the RBFF I should be able to correct this rather quickly.
  • mattmia2
    mattmia2 Member Posts: 3,177
    With the combination of the air and the pressure rising my guess is the air in the system is air that leaked out of the tank, but i suppose it could have lost the charge through the schrader leaking a little. but that doesn't explain the air.
  • HomerJSmith
    HomerJSmith Member Posts: 1,304
    edited February 12
    Have you changed the pump and what is the model of the pump? Where is the pump located on your sys?

    I'm trying to figure why the pressure on the tridicator rises from 20 psi during operation to 30 psi when the boiler shuts down. Maybe the pump is pulling the pressure down. What is the cold boiler off pressure?
  • dbsoccer
    dbsoccer Member Posts: 5
    So before I got your last message I managed to add pressure to the expansion tank. The pressure was essentially zero. And I got no water out of the Schrader valve.

    I shut the water supply valve off and drained off boiler water until the boiler pressure was essentially zero. I then added air to the tank to get to 14psi. I turned water back on and refired the boiler. It is circulating fine through the zones. I thought I may have drained off too much water and I probably did but the water is flowing. I didn't yet fix the water noise in the pipes which may be due to draining off too much water.

    And, as I had feared, my drain valve won't shut off completely and needs to be replaced or repaired so I'm dripping a small amount of water into the drain hose and out the door. Very small leak. Of course the outside temp is near zero so I don't want to mess with the drain valve until it warms up a bit.

    So now the boiler pressure is much lower - lower than I expected. I've seen it as high as 17psi when the boiler is firing and as low as 10-11psi when not or just circulating water. I'm reading the pressure gauge on the RBFF for the boiler pressure and the tank pressure. Of course I isolate the tank using the RBFF to set and check it's pressure. I would have expected the minimum pressure to match the pressure of the regulator on my water supply line. Not sure what that pressure is set at but I thought it was higher than 10psi.

    If I get a nice warm day I'll change the drain valve and properly purge all zones and see if I can get what appears to be air in the lines. I'll also double check pressure in the expansion tank.

    I have changed the pump, several years ago.
  • bburd
    bburd Member Posts: 183
    edited February 13
    The pressure range you are now seeing in your heating system is about right.

    The other water piping in the house runs at higher pressures, which would exceed the rating of your boiler and its pressure relief valve. You do not want full water service  pressure in your heating system.

  • mattmia2
    mattmia2 Member Posts: 3,177
    You could raise the pressure a little with the fast fill lever on the prv, that might help the air absorb and find its way to the air elimination.

    You can get a hose thread cap and put it on the leaking boiler drain. it isn't a bad idea in case someone accidentally opens the valve anyhow. you can even get one with a little chain you can attach to the valve
  • dbsoccer
    dbsoccer Member Posts: 5
    Thanks to both Bburd and mattmia2. Yes I understand about limiting boiler pressure below the normal house pressure and it's good to know my current pressures are within the acceptable range. This is a relief. I trying to understand the pressure a bit better. It seems the system pressure, when the boiler is cold should match the pressure set by the prv? I'm asking. The tank's bladder pressure is set, when the inlet to the tank is in open air, at 14psi but this would increase to match the water pressure when the supply water pressure is put on the inlet to the tank. This is assuming the prv is set to something higher than 14psi. And the system pressure would go up as things heat up. If the prv pressure is less than 14psi then the system pressure when the system is cold should be 14psi being set by the tanks static bladder pressure. Of course, in a multi-story house with the boiler in the basement, there would be additional pressure created by the water column above the boiler with each 10 feet of water column adding a little more than 4psi. My house is a two-story with the boiler on the first floor so I should have somewhere between 7-8 feet of water column (3 to 3.5psi) above the boiler from the second story zones. So if this is true, I am wondering why my pressure ranges between 10 and 17psi. There is something in my analysis above that is not correct. Or my pressure gauge could be hosed up. I'm reading the pressures off the gauge on the RBFF. The pressure gauge on the boiler is nearly impossible to see.
  • dbsoccer
    dbsoccer Member Posts: 5
    I shut the system down. Isolated the tank with the RBFF. Removed the tank and set its pressure back to 14psi. I reinstalled everything and refired the boiler. I am now convinced the pressure in the tank is correct and the bladder is intact. I put a cap on my leaking drain valve and will sit tight until I get a warm day to purge the air out of the zones. Fortunately because the current temp is just below 0F the boiler is working and the zones are heating as expected. Thanks for everyone's help. I'll post if purging will rid me of the running water sound in the pipes.
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