Advice on Pipes

[Balt_Homeowner]

A nasty surprise turning the boiler on for the winter: Pressure ~4psi, I opened the supply, but the system wouldn't go over 10 PSI. Waited and waited until I heard water running down the walls and saw it pooling in the basement and coming through the 1st floor ceiling.

Per my neighbor's advice, I opened the ceiling, refilled, and identified the bathroom radiator as the problem. He told me I was in luck; that radiator is on its own loop. Cap off those pipes and I'll have heat.

For that radiator, the supply pipe has a union in the basement. The return has none.

QUESTION: How to close off the return. Cut through in the middle, then either 1) Thread the end, or 2) Remove the other end from the tee it goes into and plug it.

If the pipes have been in place for ~75 years, which is the safer option? Is the force from the thread cutter more or less likely to crack the tee than unscrewing the pipe? (Hit the tee with a blowtorch to expand the metal?)

Or am I overthinking this, or should I just get the biggest wrench and heave ho?

 

[Fitter30]

Didn't write what size pipe. Take the union apart take the one side off cap the thread. Cut the return within 6" od the tee, pull the nipple in the tee. Screw in a nipple and cap. That way in union can be screwed on and will give tou what needs to xut off for the other half of the union Anytime threading or unthreading always use two wrenches. The one is a hold back so other fittings or pipe don't move. Two men would make the fitting come loose easier. One with a the hold back the other put tension on the wench and hit it with a 2 lb hammer just below the bottom of movable jaw that will shock it. Treatment after radiator leak fixed. 18" minimum 24" pipe wrenches.

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