Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

1" radiator shut off valve replacement (NPT not working)

Hi everyone,

I attempting to replace a shut off for the first time and have cut the old valve off the nipple... In hindsight probably a bad idea as the Bluefin RVST100 valve I have certainly isn't going to work (only turns about 1/3 of a turn on the nipple before stopping). This is described as being FNPT with a MNPT union. 

Have space heaters running and pulled out the caliper and am more thoroughly confused. 

From what I can tell the union side on the old valve has tapered (not straight threads) I measure the first thread at 1.7045" and the last thread at 1.735". I can't get a good measure of the female connection on the nipple as it's thoroughly destroyed.

The nipple is, I'm suspecting IPS. The unthreaded portion measures 1.3270". 
First full thread = 1.2775"
Third thread = 1.2975"
5th thread = 1.3050" 
With the difference of .0275 I'd imagine this to be tapered (If I measured properly) but it looks straight to my eye. 

I know this isn't likely to be a simple fix at this point, but would hope for suggestions on next steps or perhaps product suggestions of valves/fittings to try and exceptionally grateful for any pointers.

I don't want to proceed taking the nipple out of the radiator with a spud wrench (just yet) because I think the threading on the new union nipple might be different as nothing else seems to match up.




Comments

  • Jamie Hall
    Jamie Hall Member Posts: 23,276
    As you have discovered, radiator valves come with a union and a matching spud. Change one, change the other. The thread at the inlet to the valve should be NPT to mate with the pipe coming up from the floor -- but you'll have to take the old spud out of the radiator and use the one that came with the valve.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Insulator1214New England SteamWorks
  • Insulator1214
    Insulator1214 Member Posts: 4
    Something is still a little amiss. Unless the new valve I have is threaded incorrectly 1" NPT isn't threading on...
  • Jamie Hall
    Jamie Hall Member Posts: 23,276
    By your measurements, the nipple coming up from the floor is 1" iron pipe, and should be 1" NPT. 11 1/2 threads per inch.

    In two of the pictures you seem to be holding half of the union up against the nipple. Why?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • JUGHNE
    JUGHNE Member Posts: 11,060
    edited December 2020
    You could get a 1" iron cap to screw on there so you can have heat. Also the cap may clean up the threads if they are beat up.
    If the riser pipe has nicked threads, they can sometimes be cut carefully with a 3 cornered sharp file.

    You can wrench more on the iron cap than the brass valve to check the threads.

    Also the 1" male spud should screw easily into the inlet (bottom) of the valve to test the valve threads themselves....obviously not the correct assembly but would check threads.
    Insulator1214
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,517
    You have to change the spud in the radiator, the old one will not fit the new valve.

    As far as the riser goes try a cap as @JUGHNE mentioned spray the threads with penetrating oil and if you get the cap started tighten it loosen it, tighten it and loosen it keep doing this until you get the cleaned out.

    If that doesn't work see if you can beg, borrow or steal a 1" pipe die. Not sure if the riser is long enough to get the die on.

    Are you over an unfinished basement or on the second floor?
  • Insulator1214
    Insulator1214 Member Posts: 4
    Good ideas guy! Of course I'm petrified of breaking any fittings. Am on the 2nd floor (1st floor is unoccupied and basement is unfinished). I like the idea of using an iron cap and file to clean up the threads with loads of penetrating oil. This is what I have to work with for the nipple. There is a tiny bit of corrosion on the first few threads (and now I know this is the wrong gauge).
  • mattmia2
    mattmia2 Member Posts: 9,631
    the top of that thread is a little screwed up. It looks like the end of it broke or corroded away. It should be just fine, but it might be hard to get started. You might have to hold the valve square as you turn it for it to catch properly. What I like to do is turn it counter clockwise until i feel it drop down when the end of the threads on the fitting and the pipe line up, then turn it clockwise to thread it on.
    ethicalpaulBobCInsulator1214
  • Chris_L
    Chris_L Member Posts: 336
    You also need to consider the amount of play in the riser. From the photo of the two valves together, it appears the distance from the center-line of the outlet to the bottom of the valve is greater for the new one than the old one.

    Unless you can push the riser down (which may not be a good idea if you need it up to maintain proper pitch of the pipes), you'll have to put your radiator on feet to get the valve and the radiator spud at the same height.
    Insulator1214
  • Insulator1214
    Insulator1214 Member Posts: 4
    Thanks for all the advice everyone. Happy to say the new valve is on, it's hot with no leaks. I nicked the threads on the inside of the radiator but lamp wicking and blue block seem to be doing well. The new 1" NPT valve was exceptionally tight on the nipple but got it on after about 45 mins of cleaning the threads with a file and penetrating oil. Done!
    mattmia2
  • JUGHNE
    JUGHNE Member Posts: 11,060
    Thanks for getting back to us as we seldom get feedback. :)
    mattmia2
  • mattmia2
    mattmia2 Member Posts: 9,631
    You probably could have filed a little bit of taper on the first thread or 2 to make it easier to start