Retrofitting an elevation change in steam supply / return pipes

chriskennedy82

Hello!

Currently in the process of opening a bar in a basement space. The space is under a storefront (our upstairs bar), with other commercial businesses on either side of us. The building has central steam/radiator heating, with the boiler in the space just to the north of us (our storefront faces east). This is an old building, and the basement has never been used for commercial purposes.

Our problem is elevation: currently, we have successfully petitioned for a height variance so our 7' can be considered legal. Unfortunately, there are steam supply and return pipes (must be a dry return?) running through our space at about 6' (they run under a steel girder that bisects the space in an east-west orientation). If we cannot move these pipes up, we cannot use a good portion of the space, as we will be forced to install a partition wall right where the pipes are instead of what our current plans call for (about 6' behind them).

Our plumber said it is not possible to move either pipe, as they need to be continuously downward sloping for the entire span, and there is not enough vertical space in the basement to shift the entire span upward. This seemed crazy to me. I was an engineer in a previous life, and I know that there are various ways for steam to be directed to where it needs to go, and condensate to be removed as needed.

What we would like to do is to create two or three elevation steps in the pipes, so that they may be relocated into the floor joist area (currently running north-south, same as the pipes), and angled over the girder. I cannot seem to find anything online explaining the best approach to do this. A few design guides suggest the use of drip legs when introducing an elevation rise in a steam supply line, but there is nothing on retrofitting. I should say the existing girder/pipe intersection is located directly above where we are planning on installing the bathroom, so there will be a way to dispose of any condensate that is removed at that point.

Questions:

1. What is the best way to retrofit an existing, continuously-downward-sloping steam supply line with one or more elevation increases, in an effort to raise the average height? Can it be done? What are the major risks?

2. Same question for the return line.

We do have permission to work in the adjacent basement bays, as well as shut off building heat for a period of time, if necessary.

Any suggestions are most welcome!

Jamie Hall

It's called creative thinking -- and thinking like steam or air or water. You are quite correct in thinking that steam or air will happily go up, down, sideways -- whatever. It will always flow from higher pressures to lower (the differences in a steam system are very small, but they are there. Water, however, will not. No matter how hopeful the engineer may be, water always flows down hill.

Therefore... yes, there is no problem in introducing a dip to go under that pesky beam in either the return or the feed lines. However, you must -- repeat, must -- provide drips to a cold wet return for both of them. No options on that. The drip can be at either end of the low pipe in the "U"'s, but it's got to be there, and it has to get back -- by gravity! -- to the boiler. Further, the bottoms of the "U"'s have to be well above the water line in the boiler -- I'd use a minimum of 28 inches.

If you can do all that, you should be good to go.

chriskennedy82

Thanks, Jamie.

We were actually hoping to design something so that the pipe makes a 90* turn to near-vertical, lifting it above the girder, then re-establishing the nice, gradual slope. Resembling a sideways lightning bolt, if you will. In that case, I imagine we would need only a single drip there?

Is it possible to simply dispose of the water from the drip lines through the use of a pressurized valve of some sort? Some sort of valve that automatically adjusts release pressure to that within the system? If not, I suppose we can route the drip line backwards to where the planned partition wall is.

Thanks again for your thoughts!

nicholas bonham-carter

Condensate must return to the boiler, and cannot be disposed of.
A layout drawing would help here. The dry returns could be dropped to the floor, and run level across the floor, and the supplies could be routed anywhere in the horizontal plane, maybe placing them against a wall.--NBC

JUGHNE

When you use the term "to dispose of the condensate water" are you implying to simply waste it away down a drain so it does not have to be dealt with elsewhere?

Jamie Hall

If you go up and over and back down you will need two drips -- one from each side where the pipe turns up. Otherwise you will trap water on one side or the other, guaranteed. Anywhere there is a low point must have a drip. If you went up and then stayed up, you might be able to get away with one drip -- but watch the slopes on the now raised lines.

No, I know of no valve of any kind which will work by itself on the low pressures of a steam system.

As has been said, you can't just dispose of that water. It has to go back to the boiler. The reason is that if it doesn't, then you have to add new water to the boiler all the time that it is steaming, and that will kill your efficiency. It will also kill your boiler, and now your beginning to talk real money.

JUGHNE

Now that "condensate disposal" has gotten attention here. Here are some questions:
--- What sizes of pipes are we talking about?
--- Does the steam main slope down away from the boiler and does the return slope down towards the boiler.
---Are there any take-off tees for first floor radiators in your basement area?
---Is this a 2 pipe or 1 pipe system, (how many pipes on radiators)
---Pictures and floor plans really get interest here.
---Could the pipe coming into your space turn and wrap around your room and be enclosed in a soffit?

JUGHNE

Also, you are fortunate that you have a plumber that realizes the slope for steam piping must be maintained.

There are many postings here confirming that some believe steam can be piped like pumped water.

chriskennedy82

Thanks you all for the help. I guess I assumed that, with a big old building (~15,000 on three levels) running off a common boiler, there would be leaks, and thus some sort of auto-refill mechanism.

I will upload a schematic when I get back to the building this weekend. At the moment, I have only our MEP for the buildout of our space. We are not actually changing anything with respect to our utilization of steam (we have three radiators in the upstairs bar), hence the reason we don't have it on the plans. This is purely an effort to move the lines out of the way.

As I said, the boiler is to the north of us, two storefronts away. I think we are going to try to install a drip leg at the northern edge of our space, which will allow us to shift the supply pipe up into the space between the floor joists, and then re-connect with the steam supply on the south side of our space. I have drawn a basic schematic that is representative of why I will never be an artist.

Jamie Hall

That ought to work. Connect that drip leg back to a return to the boiler!

On your comment on the auto-fill. Some systems have them, some don't. Some folks here love them, some don't. The bottom line, though, is that steam systems -- even old ones -- shouldn't leak much. If they do, the leak should be found and fixed, as continually adding fresh water will kill the boiler from corrosion.

So... how much is "much"? Boiler manufacturers have some numbers -- it's usually in the manual somewhere -- which, in my humble opinion are 'way too high. To give you some idea, though, the system which I care for uses somewhat less than a gallon of water a month -- perhaps a quart or two -- apart from maintenance blow down, which is a gallon or so per month. And it is old -- 80 years old, apart from the boiler and one length of wet return.

Steamhead

Check out the diagrams on page 95 of Dan's book "The Lost Art of Steam Heating". One of these should solve your problem.