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How to change valve in tight spot

Hi all, undertaking a radiator valve replacement and thought to run it by this group...

The problem is that there is a small hissing leak in the connection to the radiator. The previous owner used some JB weld to try to seal over the leak but was not successful. My plan of attack was to use a Sawzall to free the radiator, change out the valve and then put the radiator back in place. 

Open to additional suggestions but my main question is...how do I replace that valve with such little clearance? I am hoping there is some trick of the trade that makes it easier.

Can provide more detail if needed...thanks in advance!


  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,833
    edited August 2022
    Remove union fitting from the valve to the radiator.
    Remove the radiator
    Close valve completely
    Remove valve handle.
    If the valve does not turn because the stem is too long, see if there is a way to remove the area of the wall or cabinet in the way
    If not, cut the pipe below the floor (hopefully from the basement)
    Once the pipe can be removed from the tight place, you can replace the valve and the radiator spud.
    To re-assemble start at the cut pipe and cut new threads on the remaining pipe or remove the cut pipe from the next fitting.
    Starting with a union fitting below the floor, rebuild the piping to the radiator with new nipples and elbows.
    Once the pipes are dry fit, then remove and tighten the pipe and fittings with appropriate pipe joint compound and thread sealer.
    Fit the assembly in place and tighten the union to the pipe and new radiator valve to the radiator union spud.
    Allow for about 6 hours of labor for this procedure.
    Allow extra time for listing to the customer complain about charging $$$$ for a valve that he could buy on amazon for only $If that valve is not a radiator type valve with a union connection, then Sawzall surgery is indicated.

    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • george_42
    george_42 Member Posts: 121
    I would cut below the valve with sawzall and remove radiator. then remove short piece of pipe left belolw tne valve . then replace valve and use close nipples and a union below valve . this may rais heigh of radiator a bit but no harm done . the hardest pat may be getting old parts apart
  • mattmia2
    mattmia2 Member Posts: 9,636
    Assuming there is a union underneath the element of that convector, you might want to look closely at the union to see if it can be made to seal before you replace the whole valve. It is also possible someone replaced the valve without replacing the spud so they are mismatched so the union will never seal as is.
  • mattmia2
    mattmia2 Member Posts: 9,636
    It looks like someone removed the bonnet of that valve to install it in the first place.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,833
    edited August 2022
    mattmia2 said:

    It looks like someone removed the bonnet of that valve to install it in the first place.

    That is what I might try first. Check that the replacement valve can also be disassembled to make the replacement easy also.My first post above was for comedic value. But I might explain that to the customer with the large price tag associated with it. Then go for the easier repair indicated here. If all goes well the the cost is less than half the quote and everyone is happy.

    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
    Larry Weingarten
  • Jamie Hall
    Jamie Hall Member Posts: 23,278
    Before you start sawing on things -- if the hissing leak is where the valve connects to the spud out of the radiator, that's a union. So -- the first thing to do is to disconnect the union (there's usually enough play) and make sure the mating surfaces are clean and very smooth. Then put it back together properly and see if the leak is still there.

    If you go with a new valve, you must also go with a new spud to match the union faces (you might get lucky and they would match -- it happens... but not often).
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    EBEBRATT-Ed Member Posts: 15,517
    Once the valve is disconnected from the radiator and the rad is lifted out you may be able to pry the pipe to the left a little but the valve will likely need to be taken apart to spin it off
  • retiredguy
    retiredguy Member Posts: 904
    edited August 2022
    If the valve is in decent shape and there is a union above the valve and that is where the leak is, I would first try an "in place" repair of the union by breaking the union, removing the radiator and trying to clean up the mating surfaces of the union. Do not use a rough steel wire brush but instead, use a fine, "brass" wire brush in an electric tool if you desire and finish off the cleaning of the mating surfaces with very fine 0000 steel wool or crocus cloth. If there are any other leaks of course repair them. When reinstalling the union, coat the surfaces with high temp RTV silicone which you can purchase at an auto parts store. I have done this many times on all size mating surfaces. If you want to remove the valve, do as @Mattmia2 suggested and remove the "bonnet" so you can spin the valve off without cutting the piping. Good luck
  • ChrisJ
    ChrisJ Member Posts: 15,671
    I'm sorry.

    I had to...

    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
  • mattyparas
    mattyparas Member Posts: 9
    Thanks for the help all! I don't think I can avoid Sawzall surgery, the previous owner used JB Weld to try to fix the leak covering the whole connection above the valve. No way to wrench it off. 

    I plan to take it out with the Sawzall and then find a new valve and spud that I can take the bonnet off to make the turn to reassemble. 

    Wish me luck! Thanks again to all. Worst case I'll call a plumber and pay $$$$ :) 

  • mattmia2
    mattmia2 Member Posts: 9,636
    The size wrenches you will need for the union and the bonnet will have no problem peeling the jb weld off.
    Larry Weingartenmattyparas