Radiator Vent Retapping

sevenmarch

Thanks Al,
I was able to find the tap at my local hardware store. Inserted the tap and slowly turned it about 1/3 of the way into the hole. It was tightly wound into the hole. Removed the tap and the vent will not grab to the threads. Not much more than it had when stripped. I can only get about a 1/2 turn on it before it slips again. Oddly, nothing is leaking from it even though it is barely tightened. I tried to go a bit deeper with the tap, but still the vent threads only go about 1/2 turn. I even tried another vent, but they both act the same.
Should I be going deeper with the tap? Are the threads past the point of retapping?

Thanks

sevenmarch_2

Word of advice?

Was replacing my radiator vent, but it looks like the threads are stripped inside. Searched to find that I may be able to retap with a 1/8 NPT (27 threads per inch, tapered). Can I easily find this at Home Depot or Lowes? Any words of advice before I tackle this project tomorrow? I figure worst case, it does not work and hire a pro to retap to 1/4 NPT next week.

Next question, the radiator in question is a larger 14 section, 5 tube (70 SQ FT Radiation) used for one pipe steam. It currently is pitched correctly, hisses loudly, and bangs a bit at the start of the cycle as well as the end. I don't think it has enough venting to allow the condensate to drip back. Maybe I am way off, but was thinking of retapping an additional vent. Should I do it at the top where their is already a screw plug for a hot water system? Cannot seem to be able to remove the current plug either. Any advice is appreciated.
Thanks

Al Letellier_9

taping rads

Finding a tap like that at a "big box" may be a problem. Either a plumbing supplier or a really good hardware store or specialty shop like Graingers would have them. That's not that big a radiator to have two vents. Any good adjustable should do the trick. A steam vent should be 1/3-1/2 of the way up the rad, not at the top.

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LarryC

Tapping NPT holes

First requirement Tapping fluid!!!!!!

If this is a one time deal, 3-in-one oil will work. Don't use WD-40 (too thin).

Using a tap handle (ideally)or Tee handle or a small cresent wrench, thread tap into existing hole gently. When snug, turn it about a 1/4 to a 1/2 turn, then back it out a full turn. Turn it back in until it bottoms again, go another 1/4 to 1/2 turn, back it out a full turn, repeat. Every 2 or 3 turns, back the tap out fully, clean off the metal cuttings, and continue tapping.

Because NPT threads are tapered, you shouldn't have go more than 1/4" to 3/8" into the metal. Go slow and cautiously.

Good Luck.

Larry C