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Hydrostatic Test Rig

I built my own hydrostatic (and compressed air, if I want) test rig. Pics are attached.

What do you guys think? Any issues with my design?

I built this because I was concerned with the quality of the radiators I purchased (long story). I wanted to test them before I have them powder coated and install them.

It has only been about 30 minutes since I started the test. I pressurized the radiator to 50 psi using a garden hose, and since then, it has fallen to 40 psi. Before starting my timer, I bled the radiator by opening/closing the valve on the end opposite the test rig several times (like bleeding brakes on a car), and also hit the sections with a rubber mallet to try to dislodge any bubbles.

I believe I read that hot water systems are typically 15 psi, and I know steam is typically less than 2 psi, so my test is probably overkill. That said, any idea why the pressure would have fallen? I'm sure it could be (probably is) a slow leak at one of the plugs that I put in.

But let's pretend that my plugs are installed as they would be for my final install (they aren't, but again, let's pretend). Is a 50 psi - 40 psi drop in 30 minutes a concern if these radiators will be running 1.5 psi steam?

Thanks for the help.


  • Jamie Hall
    Jamie Hall Member Posts: 23,635
    50 psi?

    Good heavens.  If they didn't leak before, they will now.  Steam radiators are designed with push nipples between the sections.  Over time, they can and do corrode, particularly the ones at the bottoms of the sections, and can become very thin.  For most of their length, they are supported by the casting -- but not in the short distance between section castings.  Further, the seal between the nipple and the section casting is a machined metal to metal fit -- no o-rings or gaskets or anything.  Which may not be able to withstand anything like that much pressure.

    There are several reasons why your pressure might have fallen, but the most likely is a small leak in one or more nipples.  Depending on exactly where the leak is on the nipple and how bad it is, this may or may not be a problem when hooked up to the steam system. 
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • MDNLansing
    MDNLansing Member Posts: 297
    Look round

    if you filled it with 50 psi of water and it dropped 10 pounds you should see water dripping somewhere. Look for the water and you'll find the leak.
  • mculik5
    mculik5 Member Posts: 30
    Thanks - Found Source

    Thanks for the help. As suspected, the source of the leak was one of my temporary test connections (the valve on the end opposite the tester). Fortunately, my crazy test didn't mess up the connections between sections - those areas were bone dry.

    On to radiator #2. This time I will reduce the test pressure to 25 psi.

  • ChrisJ
    ChrisJ Member Posts: 15,913

    Why not reduce pressures to something more realistic like 5 PSI.  Even that is far higher than a steam system should ever experience.

    25PSI is just abuse in my opinion.  Look at a boiler, even those are limited to 15 PSI for steam.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • MDNLansing
    MDNLansing Member Posts: 297
    5 psi of air

    then if needed, check for leaks with the tried and true spray bottle of soapy water.
This discussion has been closed.