Rethreading OLD Black Iron Pipe

AdmiralYoda

I'm trying to install a vent on one of my mains.  The end of the main is not accessible so I was thinking of cutting the pipe about 6' from the end and rethreading it.

Then I could put a union on and install a Tee for the vent.

The pipe is probably 55 or 60 years old.  What do you think?  Bad idea?

Jamie Hall

I you've got a decent threader should work. Be absolutely sure to back up the threader, though, so you don't loosen something else...

AdmiralYoda

Well I certainly don't have a decent threader...I was planning on getting a cheapy from Harbor Freight.  I'd only need to use it 2 or 3 times.

My other option is to smash the two 90's with two hammers and replace the pipe in between with a new one.  Then replace one 90 with a Tee and install the vent off of that.

JUGHNE

IIWM, I would drill and tap a 1/4" opening on the top of the main.
1/4" size can handle even a Gorton G2 air flow. You need increaser coupling. Use a long riser nipple.

STEVEusaPA

Plan B may be better for you. Wear safety goggles, not glasses.
I wouldn't buy a cheap threader just for that.
Or line up someone who has the right portable threader, cut the pipe, let them thread it. Then you can finish.

ethicalpaul

I bought a ridgid-die copycat manual threader on Amazon that has from 1/2" to 2" NPT and it's pretty good for my needs. Probably pretty similar to harbor freight.

But here's the thing. You will need a good pipe vise on a strong, anchored bench (mine isn't anchored and it's a pain), especially for 1-1/2 or 2" pipe. You probably should have a reamer too, but I get by without it by filing. And you will need a big pipe cutter to make a clean cut end to then cut the threads on.

If you're getting a motorized threader, that's a different story that I have no info about

I haven't even tried 2" with mine yet because the one time I did 1-1/2" I nearly broke my bench and myself.

If you can do it with nipples from supplyhouse.com or even a cut and threaded pipe from your local big box, I'd go that route. I mostly bought mine because I wanted to experience it and I knew I'd be cutting several threads installing my boiler. But if you can do it with nipples and fittings, do it that way.

AdmiralYoda

I'll probably try tapping it first. All I need is a Gorton #1, or maybe a #2 for overkill.

JUGHNE said:

IIWM, I would drill and tap a 1/4" opening on the top of the main.

The thing is....this isn't technically a main. The near boil piping is wrong and there are two separate mains with no header. On this main there is a split 3' from the boiler then there are essentially two long runouts to large radiators.

They are 1.25" pipe. I'm not sure if I can tap a 1.25" pipe for a 1/4" NPT.

JUGHNE

I have tapped 1 1/2" with no problem.....I think 1 1/4" would be fine.
Sometimes it is easier to dismantle the return pipes at the boiler in order to cut in a tee.
Pictures of your boiler piping would be good.

AdmiralYoda

JUGHNE said:

I have tapped 1 1/2" with no problem.....I think 1 1/4" would be fine. Sometimes it is easier to dismantle the return pipes at the boiler in order to cut in a tee. Pictures of your boiler piping would be good.

Single pipe steam, so no returns.

JUGHNE

So you have a counter flow system....steam out and condensate returning back within the same pipe?

AdmiralYoda

That's the one!  

ethicalpaul

Cool. Single pipe mains can have returns. "single pipe" refers to how many pipes attach to each radiator.

So my system has a main that goes around the perimeter of my house, and it then returns, dropping to the floor, becoming a "wet return" that connects to the hartford loop. Mine is a parallel flow system vs your counter flow system, both one-pipe.

mattmia2

I have a harbor freight threader and it was not durable at all. Granted i bought it about 6-7 years ago so design may have changed, but after about 2 dozen threads the ratchet was all loose and sloppy and it is hard to get it to turn back and catch the next step in the ratchet.

I use a unibit in a drill for reaming, it is a lot less work than a reamer and a lot easier to find.

ethicalpaul

That unibit idea is brilliant, thanks! I didn't buy a reamer because they cost quite a bit!

AdmiralYoda

Hmmmmm....I have two mains and near the boiler there is a small pipe from each main that goes to the bottom of the boiler.

ethicalpaul

Those are "drips" so that the condensate that is coming back from your radiators doesn't run back into the boiler against the steam it's creating.

At least that's what I would call it. Because your piping is not...optimal...the design doesn't match the industry norms as described in The Lost Art of Steam Heating Revisted page 137

AdmiralYoda

ethicalpaul said:

 Because your piping is not...optimal...the design doesn't match the industry norms 

Understatement of the century.  Best I can tell is the previous owners moved radiators around multiple times and made some interesting piping decisions.  

The boiler was installed in 1983 and I think they ripped up the installation manual and threw it out!

I'm tempted to try and correct it over the summer....but that's no easy task.

ethicalpaul

It may not be too bad. I did a lot of good correcting on my old boiler and it went quite well...even though I did it in the winter

AdmiralYoda

Think it would be easier to drill and tap the iron pipe....or the cast iron 90?   

PC7060

Iron or Black pipe is much easier. Cast iron is notoriously difficult to work