Hello and please bear with me. I'm no expert when it comes to plumbing but I will try to be as detailed as possible.

I'm trying to understand what a pipe does in my basement. The pipe seems to be filled with hot water and drains from upstairs down to the basement. I followed the pipe and it seems to lead to the furnace and water boiler. However from there I'm not sure if it is going to the furnace or water boiler. The pipe in question seems to be interconnected to pipes that lead to both units. I have attached some pictures of the pipes below.

Something else I was told by a plumber awhile ago was that there is another pipe on the opposite side of the wall that does the same thing that leads into the furnace room as well.

1st Picture: The is an image behind the furnace + water boiler. The pipe I'm asking about is located on the far backside on the right hand side coming through the hole.

2nd Picture: shows the pipe connections on top.

I'm new to the site, so I can only post two pictures. enter image description here

enter image description here

  • those picture links don't work for me. There are two possibilities: one is that the pipe (or copper tubing?) is part of a hot water (hydronic) heating loop. The other is that it is the domestic hot water supply for fixtures (sinks, dishwasher) upstairs. If the picture links worked, determining which should be simple.
    – Tim B
    Mar 20, 2016 at 23:18
  • Try refreshing the page once you open the window. I've had the same problem as well
    – mkng07
    Mar 21, 2016 at 0:15

3 Answers 3


The pipes behind the furnace look to be part of a heating loop. You should be able to feel that they cool off and then get hotter again when the thermostat calls for heat. Your hot water heater has a vent, so I assume it is gas fired, and wouldn't be connected to the furnace.

  • Thanks Tim, I agree and do believe it is part of the heating system. So correct me if I'm wrong. Is this how the loop works? 1. Steam travels up the pipes from the heated water boiler 2. Heats the house through the radiators 3. As the steam cools, the water condenses and goes back through "these" copper pipes and back to the boiler?
    – mkng07
    Mar 21, 2016 at 0:19
  • the condensate wouldn't come back via a dissimilar metal like copper, at least not that I've seen.
    – Tim B
    Mar 21, 2016 at 20:13
  • Would condensate normally run through galvanized pipes? It was originally a galvanized pipe that rusted out and recently replaced with copper.
    – mkng07
    Mar 22, 2016 at 1:22
  • I'm not a plumber, but usually see circuits for steam entirely galvanized. See this diagram: comfort-calc.net/Steam%20Piping/Steam_boiler_piping.JPG
    – Tim B
    Mar 22, 2016 at 3:37

Yep, that's old-timey (original to the building) Radiant Heat, the plumber should've known this right off...I'm just saying. It could be for Radiators, Radiant Floors, Snow Melting or Detached Garage heating.


The steel piping is return piping for a steam heating system. The blue box on front of the boiler is a Powerflame gas or oil fired burner. I worked on these for 35 years. The co. is from Parsons Kansas. You can't see enough of the copper tubing to see where it came from or where it goes or what it is for. The room looks cramped with less clearance than codes allow.

  • Where are the copper pipes referred to ? Boiler piping above the water line is standard steel piping or schedule 80 piping only: ( copper can be used if the connections are brazed but it is frowned upon by any real boiler installer). Also cast iron fittings are preferred over black iron. This could be a 1 pipe or a 2 pipe system. better lighting of the areas would help.
    – d.george
    Jan 12, 2017 at 12:39

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.