Steam return leak

pogy

I have an 83 year old 2 pipe steam heating system. Last night, I noticed a rusty puddle of water which appears to have come from an 1 1/2" elbow in the return system. There is about 30' of 1 1/2" pipe involved in this return system and I assume that there are other potential leaks in several places. I'm sure it needs to be replaced.

Since there is no appreciable pressure or heat involved in this section of the heating system, would PVC pipe of some sort be a practical replacement.

Brian_74

don't think so

I'm not a pro, but I believe the maximum service temp for PVC is 140°F. In theory at least, the water in the returns is close to 212°F, so I'm thinking this won't work.

pogy

Thanks but

Thanks for the reply Brian. As stated in my original post, this is a two pipe steam system. The returning condensate is cool or cold by the time it reaches the basement since it returns in a separate line. That is why I was thinking that PVC would possibly be a viable material.

Brian_74

I read that

I did read your post. I have a two pipe system myself. The traps on each radiator block the steam until it condenses. It's given up its latent heat to the room, but it can still be close to 212. It's not going to be under 140. But this is an empirical question that's easily solved. Why don't you measure the temp?

Brian_74

TLAOSH p. 142

I was curious, so I looked up what Dan says about traps. I might have misunderstood him, but on p. 142 of TLAOSH, it sounds to me like traps open around 180-200°, still too hot for PVC. And of course if a trap ever fails open, you'd have quite a PVC melted mess on your hands.

pogy

Thanks again Brian

I appreciate your comments and will certainly take them into account. I will take some temps on the return pipes to make sure they do not exceed 140 deg.. I'm pretty sure they will not but...

Will post results.

Jamie Hall

If it were my system,

I wouldn't do it.  Use PVC that is.  Yes, it is easy to work with.  And yes, in most cases, below the level of the Hartford Loop on your boiler, you will be dealing with warm return water at the highest temperature.  Above that level, you will, occasionaly, have steam and PVC will be toast.  Even below that level, I can see situations where the return water is over 140.  CPVC might survive that.



If this is a do it yourself, I can't tell you you can't.  I can only say that I'd use copper if I weren't handy with threaded pipe; I'd use threaded black iron myself.

Brian_74

You're welcome!

I think you'd need to measure the water temp and not the pipe, since the pipe acts as a heat sink.



I don't know if it's true, but I've read in some plumbing forums about people ruining PVC drain pipes by pouring boiling water down them to clear away a clog. I can't believe it's true since lots of folks drain pasta in their sinks. But it is something to think about since a PVC return would be experiencing that kind of use up maybe as much as 8 hours/day on the coldest days.

pogy

Good info

Thanks Jamie and Brian,

This is just the type of info I need to decide what I am going to do. Copper could be a way to go since a small section of copper has already been added in to the return segment when the original coal fired boiler was upgraded to an oil fired unit 20 years ago.