Capping versus new fittings on old pipe

garfungle

I'm removing a radiator and repiping a second radiator. This is forcing me to modify some very old (what I believe is painted cast iron) piping. I do not want to damage the larger OD pipe for the supplies and returns for all the radiators since it would be a pain to fix. I've been reading about different fitting removal techniques. I was wondering what everyone's opinion is on which would be the best repiping approach with low risk. I am leaning towards sawzall nipples and then using the hammer technique to break the fittings, but I can't tell if this will disturb the larger supplies and returns. Also, I'm not sure which fittings I should remove because I could cap some of the old lines without attacking the fittings on the larger pipe, or I could just attack the fittings on the larger pipe and put a proper fitting on the new repipe. I wasn't sure if capping supplies and returns is worse on performance rather than just installing the correct fitting. I've attached a picture with an example of what the supply side of the radiators looks like with the two different approaches. Additionally, on this pipe, it looks like there is solder on the threads, but I can't really tell since it's been painted silver. Did they sweat these pipes or is this just painted pipe dope?

mattmia2

It is paint and possibly dope or corrosion. Either little stub won't hurt anything as long as it is arranged so that condensate can drain. I would cut most of the way through the band of whichever fitting is easer to reach and hit it with a chisel with a second large hammer or other casting behind the fitting then cap whichever stub. There is a possibility that close nipple could disintegrate in the process because the process of threading it makes it a lot thinner than a piece of pipe.

Is this 2 pipe? How is the main vented?

garfungle

It's two branches where the radiators are piped in parallel. The boiler is vented out the chimney. What do you mean so that the condensate can drain? Maybe I didn't specify that this was a boiler, so it's a closed system. Do you just mean if I'm draining the boiler, anything trapped in that pocket needs to drain via gravity, so I need some slope?

Ok, so you're suggestion is to attack the larger fittings? It'd probably be easier for me to attack the tee. Is it better to try to back the pipes out before attempting the two hammer method or is there very little risk to me damaging the larger pipe with the two hammer method? I know sawzall into the tee could risk damaging the threads on the larger pipe.

mattmia2

This is a converted gravity hot water system, not a steam system?

garfungle

Yea, it's a hydronic heating system. No steam.

mattmia2

I'd pick whichever fitting is easier to get a saw or angle grinder too, the stub won't make a difference if it is the riser to the runnout or the end of the main. If you carefully cut the fitting until you are almost to the threads then you can split it with a chisel and it will unscrew easily.

Cut off the rest of the piping so you can unscrew it.

It shouldn't be a problem with just one emitter at the end of the main, but if you make too many changes to what was a gravity hot water system you can affect the balance.

EBEBRATT-Ed

The easiest and safest way to remove a fitting is to use a 4" angle grinder and cut into it and stop short of hitting the threads. Make two cuts one opposite the other if access allows. Then drive and old screwdriver into the slot the grinder made and it will pop apart easily.

Pounding with hammers is ok if done with a proper back up but you run the risk of causing a leak elsewhere.

Sawzall is ok also but more difficult to control depth with vibration and shaking.

garfungle

Does that same technique you guys are suggesting work on galvanized fittings? I have a couple of those in the system. I'm pretty sure I can't just use the two hammer method without a cut like you guys are suggesting on the galvanized fittings.

EdTheHeaterMan

Galvanized fittings are usually malleable iron that has been galvanized. Malleable fittings do not break as easily as cast fittings. I. believe that the galvanized fittings may unscrew easier than Cast fittings. That is my experience anyway. Applying heat and using mechanical leverage is often more effective. A compound wrench can be very effective.

Before I could afford one of these, I used to place two wrenches on the joint I was trying to separate and use some extension pipes for leverage and a come-along for the mechanical leverage required. like this: