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Move to pressure testing with water?

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basline
basline Member Posts: 2
in THE MAIN WALL

I'm installing my own hydronic heating and cooling system running on a heat pump, with a lot of help from Siegenthaler's most recent edition book and some tradesmen. I'm pressure testing the mechanical room plumbing, and I've hit the point where input from others would be appreciated, as I'm not sure if I have tiny leaks or should move forward.

I've been pressure testing with air, taking the system to just above my operating pressure (testing at 35 psi). I've found all the obvious leaks, but I'm still seeing pressure drift down slowly. It's slow enough that I'm convinced there are no more big leaks, usually ~ 2 psi in 24 hours. There is a lot of volume in the mechanical room portion of my system, including a ~40-gallon buffer tank, so it's hard to tell if the pressurized air is cooling off to the basement's temperature, or if there are leaks I'm missing.

I've started insulating my copper pipe, and just yesterday found a very slow leak with big blu micro leak detector (took about 10 min for small bubbles to form, and they were hiding on the back side of the fitting). Now I'm doubting myself, and I'm concerned I need pull off the insulation.

Before I started insulating, I used megabubble or big blu on every threaded fitting (all other connections are press or sweat done by a plumber). I thought this was good to go, but I missed at least one very slow leak. I've also tried an ultrasonic leak detector now that I've started insulating, but it isn't registering any leaks, including the very slow leak I just found.

Should I crank the pressure up with air? I assume that would make it easier to find leaks? The pressure relief valve is rated to 45 psi, but I could just plug the outlet side and let it open. The buffer tank says to not run above 90 psi water pressure, but I'm a little anxious loading up that much volume air pressure close to 90 psi, as that is alot of energy if something fails.

Should I just fill my system with water before finishing insulation and see what happens? The heat pump must be commissioned in heating mode, so I can do it without finishing the insulation. Once it's commissioned and apparent that it's leak-free, I'd finish insulating and finally run chilled water.

My family is starting to stare daggers at me; it's getting hot here. Any suggestions on the next steps would be appreciated. Given the need for cooling, I'm hesitant to let the system sit under pressure for multiple days to test it, but I also don't want to make any more rework for myself.

Comments

  • hot_rod
    hot_rod Member Posts: 25,357

    can you isolate the buffer tank and test with water?

    Water, especially warm water will wash out flux and oils also, which may he masking a bad solder or thread joint

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,898

    Hi, The risk of testing with water is you find a leak at a low spot in the system that cannot be cleared of the water to resolder. Did you install drains at low points? Can you use air to blow water from the system? Can you use something other than solder fittings, so cutting out a bad connection and redoing it isn't a problem, even if wet? 🤔 There is always a way… and it doesn't have to involve Bandaids.

    Yours, Larry

  • mattmia2
    mattmia2 Member Posts: 13,505

    Do a hydrostatic test. use water. If the emitters are connected usually those are only rated for somewhere around 30-40 psi. The more volume in the system the bigger the leak has to be for the pressure to drop in a given timeframe. You will likely see water dripping out somewhere. You could have made a test rig with an air fitting or schrader and gauge and tested sections as you assembled it. I like to put a piece of tape on the gauge and make a mark at the needle and one or 2 of the scale markings so you can tell you are looking at it at the same angle by lining up the marks to the scale markings so you can detect small movements in the needle. I think there was a thread where I did the math on expansion of air a couple years ago and found that you needed to go from like freezing to hot summer day for the expansion of the air to be significant.

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 18,248

    Air changes pressure as the temperature changes so it is always a little erratic.

    Nitrogen or CO2 are good as they change pressure less.

    At this point I would probably use water and raise the pressure to 50 to find the leaks faster

  • mattmia2
    mattmia2 Member Posts: 13,505
    https://forum.heatinghelp.com/discussion/comment/1858532#Comment_1858532

    A shop vac is good for removing water from low spots too.

    Larry Weingarten
  • basline
    basline Member Posts: 2
    edited June 23

    Thanks all. Sounds like I should just bite the bullet here and start filling the system. I do have a drain in my buffer tank, which is the lowest point, and a couple of other drains in lower points, but I will probably have an issue with water in the pipe if it comes down to it. I have access to a press and can use press fittings if needed.

    I can isolate the buffer tank, but a couple of my shutoff valves have a foot or two foot of 1" copper.

    Odds are slim that I will ever undertake this again (it's going to take a while to make it for this with the spouse), but next time, I will test sections as I go. For the record, I did this with the emitters; it's just been the mechanical room where I feel down on this.

  • mattmia2
    mattmia2 Member Posts: 13,505

    Of course all of the piping system gets smaller when it gets colder too…

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