Home>Discussions>BATHROOMS>About a 2 pipe radiator and how to disconnect it
7 posts / 0 new
Last post
About a 2 pipe radiator and how to disconnect it

We have a very small bathroom on our first floor. And it has a 2 pipe radiator. To get some space back in the renovation, we are putting in radiant floor heat and taking out the radiator. (Long story)

The recommendation seems to be to cap off both pipes. But I wonder why no one recommends that we connect the 2 pipes under the floor so the water at least circulates. The pipes that run in the basement ceiling help keep the basement warm in the winter. If we just cap off the pipes, does that mean the water won't circulate anymore and the basement will be colder in the winter?

How does the 2 pipe radiator work. Is each radiator self-contained? None of our plumbers really explain it well. Aside from the possible side effect of making the basement colder, I don't want pipes sticking up out of the floor. Can we cap the pipes under the floor? All I see ****** are mostly articles about 1 pipe radiators and that's not what we have. Can anyone explain how it works? Thanks!

Re: About a 2 pipe radiator and how to disconnect it

Two-pipe systems are usually hot water systems; one-pipe systems are always steam. With the two-pipe systems, they can either be gravity (convection) flow, or they can be pump-driven.

Usually there is a main supply line and a main return/drain line; both supply several radiators. Capping the lines won't block the flow in these main lines. However, it will stop the flow in the branch lines supplying that individual radiator.

If you loop the supply and return/drain lines together when you remove the radiator, you may end up reducing the flow through other radiators on that supply/return system. You would need to install a control valve to reduce the flow through this loop. If your system is pump-driven, you could simply install a radiator in the basement on that branch line. If it's gravity flow, then you might mess up the convection currents by looping things together without careful design and planning.

You can certainly cap the pipes under the floor.

Re: About a 2 pipe radiator and how to disconnect it

They can also be caped in the basement.

Re: About a 2 pipe radiator and how to disconnect it


As you seem to imply in your post, you realize that your new radiant heating system is really a separate system that usually heats the house by plastic (PEX) tubing that is often buried in low-density concrete, or sub-floor PEX tubing that is connected to the boiler, with the hot water being pumped throughout the house---ordinarily the 2-pipe system that formerly heated the house is disconnected & the open pipes that formerly heated the house are left in place.

On the other hand, the installers may have simply just modified the BATHROOM heat & left the rest of the house on the old heating system----they may have simply created a RADIANT ZONE just for the bathroom by creating a separate hot water zone going back to the boiler, & left the rest of the house on the existing heating system????---in such a case it would be an easy matter for them to connect the existing older supply piping to add more heat to the cellar. Does the bathroom now have its own T-stat that the workers installed just for the radiant heat???

You'll have to talk to the installers once again to try & understand how they modified the piping in the heating system.

You will have to ask the installers of the radiant system if they buried any PEX tubing in the cellar floor to offset the cold cellar temps that you might experience in winter---it seems like a good idea to connect the old copper/steel pipes to the radiant system to get added heat to the cellar, but this would involve additional labor/plumbing materials if indeed you do have a problem with cold cellar temps---have you asked the installers about this issue????

I've included some references to piping diagrams that are widely used in hydronic (hot water) heating systems so you can study how the boiler pumps the hot water thru the piping systems when the T-stat is turned up to call for heat.

Go to Google and enter "images for radiant floor heat" to get an idea of how radiant floor heating piping is laid out & how it works.

There are at least 3 different ways that your old radiator pipes can be arranged (piping arrangement) so that the pump at the boiler pumps the hot water thru the piping/radiators, then returns the cooled water back to the boiler to be reheated.

Also go to Google and enter "images for 2-pipe hydronic heating system"
Also Google "images for 2-pipe direct return heating", and "images for 2-pipe reverse return heating" and "images for single pipe hydronic system"

If the current radiant system now adequately heats the cellar, there would be no need to incur the added expense of connecting the old pipes to the new radiant system, so talk to the installer to determine what's best.

Re: About a 2 pipe radiator and how to disconnect it

Thanks for all these suggestions. I appreciate everybody's advice. I should have been more clear. The new radiant heat in the bathroom is not water-based. It is electric underneath tile. The work is just starting. The old radiators will no longer be needed.

We will speak with the plumber when the radiators get taken out.

Thanks again!


Re: About a 2 pipe radiator and how to disconnect it

My bathroom is old...the diverter knob on my tub spout is broken and needs replaced...what is the procedure for replacement?..

Re: About a 2 pipe radiator and how to disconnect it


Start by posting under a Topic other than one for a 2 Pipe Radiator. A bathtub has nothing to do with a steam radiator heat.

There are so many variables, I would not know where to begin with an answer to your question. Purchase a book on Simple Home repair and start there. Or remove the handle and start digging into the situation


Handy Andy In Mt Airy NC

Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.