I'm currently remodeling my basement and it's a great space, but unfortunately, I have 4 gigantic 3 inch cast iron pipes running the full length of the house that carry hot water from my gas boiler to the radiators. When they were installed in 1937, they were installed at a height of 6 feet from the floor (I guess people were shorter back then!). Obviously, they make the space pretty unlivable, so, I'd like to remove and replace them with copper pipes which I will tuck up into the rafters (obviously leaving a little space around them) and use dielectric joints to mate the new copper pipes to the existing cast iron radiator feeds. Has anybody attempted this? I have worked with 1/2 inch copper pipes before (I've already ran the plumbing for the basement) so sweating and soldering is not a problem.

Another question is, the pipes coming out of the boiler (from the 70s) are 2 inch copper and they are joined to the old 3 inch cast iron pipes. Is there really a need for those giant pipes? Since the copper pipes coming out out of the boiler are 2 inch, I see no reason why all the pipes carrying hot water to the radiators couldn't be 2 inch. I'm assuming the large pipes were from an old steam system so they needed to be larger.

Thanks in advance for your advice. This is my first post, so please be gentle!

 

There is a good possibility that the large pipes can be replaced by smaller copper. First question is if it is a steam or hot water system. If steam, then don't read the rest of my post, I am steam dumb. The remainder of this post is based on a hot water system.

The other question is if this is still a gravity system or have circulator(s) been installed?

If still a gravity system then the pipes need to remain as is. It is designed for the hot water to rise and the cold water to sink which forces the water to circulate.

If a circulator has been installed there is no longer a reason for the large low hanging pipes. In this case a check of the radiation needs to be made. The size, type, and number of rad's on each circuit needs to be known.

From this the BTU's of radiation can be calculated. From that the size of the pipe can be calculated. This way the pipe is sized properly for the required transfer of BTU's.

This should get you started and give an idea of what needs to be done. There are others here that I'm sure will also help out.

Al.

 

Thanks for your help Al, this system is indeed a hot water system. The water is circulated through the system by way of a water pump (I'm assuming that circulator is another term for a pump).

 

I am also in the same boat. I have started the basement remodel project in our house. The house was built in 1930 and has multiple 3" pipes hanging all around the basement. I had a plumber come out this morning to asses all of the jobs that need to be done. The quotes are pretty high. I think with a little friendly advice this is a job that can be accomplished as a DIY project.

Aaron, if you have started this project please post some of your education for the rest of us.

The plumber made the same comments regarding pipe size as mentioned by Al. They recomended moving to a 1" copper (L), moving it up in the joists, high and tight along the exterior walls where applicable.

My question is where to look for advice on replacing the large valves with fittings at the radiator with something that works with the 1" copper.

 

You don't need to know the radiator size you need to know the heat loss in that area for pipe sizing. The radiators only need to match the heat loss. This will allow smaller pipes and pumps.
Check this link for pipe sizing when heat loss is known.
Technical Menu
Look in the Hot water menu for pipe size in the right column