Home>Discussions>PLUMBING>mono-t radiator system
4 posts / 0 new
Last post
mono-t radiator system

We are remodeling the kitchen and had the radiator moved from under the sink (that's right -- under the sink) to a new location. As I understand it, our system has one major pipe with water running through it and pipes going off of this main pipe to and from the radiators and back to the main pipe. The plumber simply took the pipes that go up to and away from the radiator and turned them and ran them over to the new location, leaving them tied into the main pipe as they were originally.

We called a different plumber to hook up the radiators who told us that the pipes were too far away from where they tied into the main pipe. He said that they could not be more than six feet away -- they are currently at least 12 feet. He tells us that he will have to redo them, draining the system, etc. kaching, kaching, kaching...

It is a hot water system and we've been told it was a mono-T system. So, which plumber is right???

Re: mono-t radiator system

Without any photos to look at, and only the info you put in your post, it sounds like the first plumber is right; why did you see the need to get a 2nd opinion from another heating tech/plumber???

Was there some problem with the initial radiator installation???

It's not a good idea to have 2 different plumbers working on the same job---the 2nd plumber may refuse to touch the work of a previous plumber.

The proof of course is in the pudding----turn up the thermostat to get the heat going, & see if the radiator heats up as it should.

Some homeowners take issue with the appearance of the piping if it snakes across the kitchen wall or floor; but if this is not a problem, then heat performance is the main issue.

The 2nd plumber is wrong if he says that the pipes/radiator should be no more than 6 feet from the main pipe---the mono-flo tee system (also known as venturi valves) is a tried & true method of getting the hot water to the radiator and a 12' stretch is not that exceptional; sometimes pockets of air can get trapped in longer than usual piping, especially if it is copper tubing (rather than PEX tubing) and has a lot of twists and turns (read elbows); in such a case the air bleeder valve on the radiator can be opened periodically to let the air out.

Again, turn on the heat and see how the new extension performs---the radiator should eventually get too hot to touch, and there should be no "sloshing" noises in the pipes, which would indicate some air in the piping.

It's good that you had room in the kitchen to keep the radiator there---they put out lots of heat and will last for decades; since the kitchen is loaded with appliances and kitchen cabinets there is often no room for the radiator; in such cases one or two kickspace heaters are installed at the base of the new kitchen cabinets and the piping is hidden behind the cabinets.

In the piping diagram below, the radiators seem to be a few inches from the monoflo-tee & the main piping---in reality the supply/return piping usually extends 10 to 12' from the main.

Often a repair like this requires ONE monoflo tee installed in the return piping, if there is not enough heat delivered to the rad, ANOTHER monoflo tee can be installed in the supply piping to the rad.


Re: mono-t radiator system

I agree with Pelton. If it had to be within 12' of the main there would be no heat to any 2nd floor rooms.


Re: mono-t radiator system

Pelton, thanks for the information. Just to answer a couple of your questions. We didn't feel the "need" to get a second opinion. We wanted to hook the radiators up and the first plumber could not come out for a couple of weeks, so we called someone else.

Secondly, we needed to relocate the radiator because in its original location (under the sink) 1) it took up all the space in the cabinet under the sink so there was no storage and 2) it got very hot standing in front of it and preparing meals and 3) it was very difficult to work on plumbing with the radiator in the way.

I'm hoping to solve the problem prior to hooking up the radiators and turning them on so that we don't have to pay to have a plumber standing around a second time waiting for the system to drain and then fill back up.

What you say about the radiators reaching to the second floor does make sense. I can see where the pipes for the second floor units tie into the main pipe, run over about 2 feet to the wall, turn up and go up about a foot and then disappear into the wall. They run up the wall at least 10'(the height of the first floor ceilings)to the second floor. If they could be no more than six feet from where they tie-in, the second floor radiators would not be working.

Thanks for the input.

Sponsored Stories

TV Listings

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