A T junction of the galv water pipes under the house carrying water to the outlets of the house has some corrosion. I have got the pieces required to replace the broken ones, but I have a problem in that I can’t unscrew the stupid galv piping from the T junction. How do other people replace bits (it is obviously not easy to unscrew a piece of pipe which was screwed in so that it wouldn’t leak….)
Sounds like you are trying to take a piece of pipe out between fittings. Well take a hacksaw and cut pipe through and use 2 wrenches one to pull and the other to hold back on fitting, When you put it back you need a union and a nipple and then measure the space you have allow for threads and have it cut. Sounds like you jumped the gun, if you never did this before you are in for a suprise.
If your problem is not that which has been explained by Retired plbg and is just that you cannot remove a jammed in fitting that has been screwed into a tee fitting = try applying heat to the joint then using a couple of pairs of wrenches it can usually be undone.
Selgas Services Ltd Craftsman Gasfitters, Plumbers, Electrical Service Technicians
In reply to message posted by Retired plbg: … When you put it back you need a union and a nipple…
Just to clarify what RP means by “a nipple:” you will need a special nipple that has reverse (male) threads on one half or a more commonly available special coupling, with reverse (female) treads on one half. These fittings allow you to tighten the pipes together by turning the special fitting in one direction. The union is the easiest way to go, but the reverse-thread fittings may be required if you plan to bury the connection in a wall or you are running gas.