NPT fitting doesn't quite fit in NPT tap!

[Reach4]

I think some paint matching the radiator would be nice. Mask the vent, and paint the other. I know the paint is not going to actually adhere to the tape, but I am assuming the paint film will hold together over the tape.

Plastidip spray paint can be nice. If you don't like it, you can peel it off with your fingernail. Obviously you need to mask a big area when using spray.

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[DIYorBust]

So that brass fitting is a check valve? Never used a auto air vent on a radiator just a coin vent just in case the vent would start leaking possibly ruining everything under it.

It's a service check so you can change the air vent, normally would go right under the vent, but I had it and it's npt so I tried this.

I here you on the auto air vent, but this is a minical float vent with a hygroscopic safety cap. If the float fails the cap will expand and stop the leak, and the failure will be discovered when the radiator no longer vents. I generally use the the coin vent too, but for some radiators that need frequent venting or are in tenant spaces I feel comfortable with this. Maybe I'm wrong but so far no leaks.

 

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[DIYorBust]

threads are threads . only th ing I can think of is poor manufacturing or even possibility of that bushing being 1/2 npst (straight thread i think my abreviation is correct) It would be a rare type fitting but sure sounds like a straight thread .

I wondered if they threaded it straight, but I'm thinking maybe they over threaded for the metal thickness.

 

[DIYorBust]

I think some paint matching the radiator would be nice. Mask the vent, and paint the other. I know the paint is not going to actually adhere to the tape, but I am assuming the paint film will hold together over the tape.

Plastidip spray paint can be nice. If you don't like it, you can peel it off with your fingernail. Obviously you need to mask a big area when using spray.

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I hear you, but I'm trying to do a nice job here and npt to npt should ideally not require plastidip.

 

[wwhitney]

So is the hex piece a bushing, and if so is it possible to replace it? Assuming you could find one that is not overtapped.

Cheers, Wayne

 

[DIYorBust]

The hex piece is a service check valve meant to connect to the air vent so you can change the air vent without draining anything. I could put an npt nipple and coupling if I can find one that fits, it just looks crappy.

 

[Reach4]

See hex marked in red.

The hex piece is a service check valve meant to connect to the air vent so you can change the air vent without draining anything. I could put an npt nipple and coupling if I can find one that fits, it just looks crappy.

Attach file

 

[Jeff H Young]

So is the hex piece a bushing, and if so is it possible to replace it? Assuming you could find one that is not overtapped.

Cheers, Wayne

looks like a bushing thats welded in. not sure the exact fitting used though Ive worked with soc-ol- et weld o let and many welded pipe fittings .
Also just not really sure what his problem is, Id take a known good 1/2inch nipple and screw it in and figure out whether its the radiator or his other fittings and take the guesswork out

 

[wwhitney]

Also just not really sure what his problem is, Id take a known good 1/2inch nipple and screw it in and figure out whether its the radiator or his other fittings and take the guesswork out

Right, if a nipple screws in securely, the street elbow can be replaced with a regular elbow and close nipple, or a slightly longer nipple if necessary for the nominally overtapped opening.

Cheers, Wayne

 

[DIYorBust]

Thanks guys. A good 1/2 inch nipple does seal, but the "bad" fittings work fine in other tappings.

Well I think wayne's idea might give me what I need. It's a bit more work to make it look good, at that adds up with multiple fittings per radiator on a dozen radiators, but it is what it is.

 

[wwhitney]

"bad" fitting

Have you tried other street elbows? Since the one in the picture is chromed, I wonder if it was slightly overthreaded to allow for the thickness of the chrome layer, but they overdid the overthreading.

Cheers, Wayne

 

[Reach4]

https://www.engineersedge.com/hardware/standard_taper_pipe_threads_npt_15544.htm has dimensions for NPT threads. For your chrome street elbow, does the largest thread have diameter of 0.95429?

https://www.thomasnet.com/articles/custom-manufacturing-fabricating/all-about-pipe-and-hose-threads/ is a similar chart.

I might be misreading some of the info.

 

[DIYorBust]

Well its true I did not try another street elbow, I don't have one on hand. I'll try to find my calipers to check the threads. But the street elbow does seal fine with the check valve and it get easily hand tight with my copper npt fittings.

 

[Jeff H Young]

its interesting when you have time to track exactly the problem but it boils down to 2 mittings thatr either they mate well or dont which one is "bad" dosent really matter or they could both be at opposite ends of tolerance. Im only guessing you never figured out if the radiator is truly tapped as a straight or tapered thread i can tell by running my finger inside and feel the taper, just a wild guess it might not be tapered.
frustrating I know you spend all this money and time and have a poor fit up even worse (or equaly) when a professional fitter has to deal with this and it makes him look bad plus trying to make money. I have about 5 minutes to make this joint up if Im going to eat tommorow ha ha.

 

[Fitter30]

its interesting when you have time to track exactly the problem but it boils down to 2 mittings thatr either they mate well or dont which one is "bad" dosent really matter or they could both be at opposite ends of tolerance. Im only guessing you never figured out if the radiator is truly tapped as a straight or tapered thread i can tell by running my finger inside and feel the taper, just a wild guess it might not be tapered.
frustrating I know you spend all this money and time and have a poor fit up even worse (or equaly) when a professional fitter has to deal with this and it makes him look bad plus trying to make money. I have about 5 minutes to make this joint up if Im going to eat tommorow ha ha.

if you were using a Spirovent and bladder style expansion tank wouldn't have to constantly chase air.

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[DIYorBust]

I am using those things but I still get a lot of air, partly because the building is tall and perhaps not all the lines are pitched to a vent, but also because we have been draining it frequently while we work on the system. Perhaps later I will put the manual valve back in. The valve ot shipped with has only 2 threads and a rubber gasket, but it also shipped with npt x ftg adapters that are intended for the same spot, you can supply the radiator on top if the situation requires.

 

[DIYorBust]

I am using those things but I still get a lot of air, partly because the building is tall and perhaps not all the lines are pitched to a vent, but also because we have been draining it frequently while we work on the system. Perhaps later I will put the manual valve back in. The valve ot shipped with has only 2 threads and a rubber gasket, but it also shipped with npt x ftg adapters that are intended for the same spot, you can supply the radiator on top if the situation requires

its interesting when you have time to track exactly the problem but it boils down to 2 mittings thatr either they mate well or dont which one is "bad" dosent really matter or they could both be at opposite ends of tolerance. Im only guessing you never figured out if the radiator is truly tapped as a straight or tapered thread i can tell by running my finger inside and feel the taper, just a wild guess it might not be tapered.
frustrating I know you spend all this money and time and have a poor fit up even worse (or equaly) when a professional fitter has to deal with this and it makes him look bad plus trying to make money. I have about 5 minutes to make this joint up if Im going to eat tommorow ha ha.

its interesting when you have time to track exactly the problem but it boils down to 2 mittings thatr either they mate well or dont which one is "bad" dosent really matter or they could both be at opposite ends of tolerance. Im only guessing you never figured out if the radiator is truly tapped as a straight or tapered thread i can tell by running my finger inside and feel the taper, just a wild guess it might not be tapered.
frustrating I know you spend all this money and time and have a poor fit up even worse (or equaly) when a professional fitter has to deal with this and it makes him look bad plus trying to make money. I have about 5 minutes to make this joint up if Im going to eat tommorow ha ha.

Thanks, it is definitely not supposed to straight, but anything is possible. What could be done if that is the case?

 

[Jeff H Young]

I am using those things but I still get a lot of air, partly because the building is tall and perhaps not all the lines are pitched to a vent, but also because we have been draining it frequently while we work on the system. Perhaps later I will put the manual valve back in. The valve ot shipped with has only 2 threads and a rubber gasket, but it also shipped with npt x ftg adapters that are intended for the same spot, you can supply the radiator on top if the situation requires


Thanks, it is definitely not supposed to straight, but anything is possible. What could be done if that is the case?

no it definately shouldnt be a straight thread, and you shouldnt be having this problem of threaded fittings . a straight threaded joint usualy has a gasket against the shoulder of the male fitting piece .

 

[Jadnashua]

Metric threads?

 

[Jeff H Young]

Metric threads?

never heard of metric pipe threads thought they used NPT all over the world .