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Mysterious leak/loss of pressure

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BigMak
BigMak Member Posts: 44
in THE MAIN WALL
I have a single line baseboard system loop, 4 zones. one of the lines wont hold pressure, but isn't leaking water. where is my pressure going.

I just finished up re-piping system, a lot of new valves, pipes, fitting, and components. I filled system with air (air first incase i had to re-solder , and again with water. I tested and isolated each boiler-OK. each line-3 out of 4 ok. One line was leaking air pressure, sprayed soapy water on all the fittings i replaced. Nothing detected. Then i filled with water, still no visible water leaks.

How am I still loosing pressure, and should I see some evidence of this? I'm puzzled. Any one ever encounter this? Possible solution or additional trouble shooting?

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  • Jamie Hall
    Jamie Hall Member Posts: 23,350
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    Somewhere, somehow, you are losing water in that line, and it's perfectly possible to do so without seeing it. The best option is that one of the valves which you are using to isolate it is leaking. Not much -- it takes very little -- but just enough. The easiest way to test that is to fill the whole system to some handy pressure -- say 15 psi with water, and see if the whole system will hold pressure. If it does, then close the isolation valves and reduce the system pressure to something handy, say 10 psi, and see what the offending line does. If it drops to system pressure and then stays there, there's your problem.

    However, if it flunks that... you need to inspect the whole offending loop, and you're looking for a very small leak.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    BigMak
  • BigMak
    BigMak Member Posts: 44
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    @Jamie Hall, that makes sense. The 2 valves in question are brand new. Wouldn't have thought of them being an issue. I just even new stuff can be defective. So, I filled to 20PSI, let's see how this goes. I hope you are right. Thanks for helping me see the tree in the forest. Now the question is, do I want to go and extract that tree or leave it?

    Any suggestions on initial fill and start up. How long do flush lines/boiler? etc.
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,646
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    I've seen plenty of new valves where the packing leaks, or.....the ball leaks past. Making a zone look like a leak. 

    Do as Jamie suggested. Valve out the makeup water and let the entire system sit for several days. Watch the pressure. It shouldnt drop. If it does the water is going somewhere. The boiler held air pressure correct?
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • JUGHNE
    JUGHNE Member Posts: 11,067
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    Can you isolate or disconnect the expansion tank?
    Don't test over 30 PSI or relief may open.
  • BigMak
    BigMak Member Posts: 44
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    Jamie was right on the money. knew exactly which one to. The other end of the loop was the valve to the boiler and I Knew that one was holding tight. Change the valve, somewhat reluctantly, but I was all setup and if I didn't do it now I'd never do it. I can begin to tell you thoughts of doing all this work and have something not respond as predicted, is a nightmare. I'm walk around the house with a flashlight look at ever inch of baseboard, saying to myself, "Where is this god dame leak!!

    over 30#, I keep it under 30. Don't know how much pressure this boiler can take, wish I did, ss well as the BTUs it's build for steam. 75yr. judging the original temp/pressure 30# is red line, pins the needle at 50#.

    problem solved

    thanks again

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