thom

The installation is an old steam heating system. The existing 2" piping is run underground, and uninsulated. There is a leak.

I understand the system is past it's useful life and needs replacement. The non-profit that owns the building barely scrapes by. It lacks adequate resources.

A member of the organization has dug up the leaking pipe. There is a leak in the steam piping, a hole about 1/16" diameter. It is in a location that makes replacing the pipe difficult. Furthermore, it would require cutting out the section and installing a couple short sections and a union. I have no confidence that the el's we would be connecting to would be clean.

What is the best way to repair this pipe, even if temporary? Weld it? Clamp around pipe with soft (rubber) patch?

mdshunk

You can get as much tied up in a welder's services as you would replacing the pipe. They won't leave a steam line in a condition they're not 100% sure of the success of their repair. Bite the bullet, cut the pipe out, and get a 2" NPT thread chaser or wire brush for your drill to clean up the ell's threads, and have a great day.

thom

Thanks MD.

This is an old system. 60 years or so. The outside of the pipe is quite rusted, I assume the inside is worse. What is the likelihood that I won't end up chasing a useable connection forever?

K2

Steam or a hot water heat system does not corrode like your domestic water supply because the hydronic systems are closed and not enough Oxygen is introduce into the system for oxyidation to occur ... So the inside of the steam pipes are probably in great shape or at least any I've taken apart were.

Leaks in Low pressure steam pipes are almost like leaks on forced air ductwork. In areas like mine with low humidity the old timers often left little permanent outlets to humidify the house. I have a few of those and a few minor leaks around some steam traps. I don't even think about them.

High pressure steam I really don't know much about.

If I had a leak in a low pressure pipe that was 1/16 in diameter I'd run a tech screw in it and it would probably last a thousand years or so.

thom

great idea about the tech screw, thanks

mdshunk

Uh... no, it's not. It's a great band-aid. Maybe that's how you roll?

K2

Band aid stops the bleeding and the body heals. Steam pipe at 3 psi can also seal itself.

Grumpyplumber

Duct tape!

thom

MD, I agree that band-aids are less than optimal. This is a tough site. The location is between a building/foundation and a retaining wall so it's a hand dig and the burden must be removed by wheelbarrow because of lack of space (the area is only about 4' wide (the boiler is in an adjacent building). The soil is sand with 4" river stone. The stone makes shoveling really tough. The leaking pipe is the riser that brings it up from the lower to the upper grade. Digging it out would require digging about 8'deep. The leak, at least the one that is now exposed is down about 30".

Digging a pit to work in, in this location, is a lot of work, which is why I was looking for a patch to begin with.

The system is old and needs replacement. I suggest to them 6 years ago that they needed to replace the system and that forced air would be a better alternative. Lack of money is a real issue.

This repair is a freebee on my part. This non-profit is my black hole. Over the past several years I've donated more than $10,000 in materials bought specifically for them plus donated hundreds of hours of labor. The building is historic, built in 1903, and truly is a money pit.

K2

So is it low pressure?? I'm curious as to how they knew it was leaking??

wrenchman

Water piping in a hydronic system developes a coating (iron oxide,the black nasty smelling stuff) that acts as a lubricant on the walls of the pipe. This is not the case with steam, high or low pressure. Horizontal steam piping is eaten away on the bottom by condensate that is pushed against the pipe by steam pressure around it. Vertical runs are usually not affected by this situation.

This being said, if the hole is one the bottom, replace the piping to the closest vertical run on each end. If the hole is one the top or side, use a repair clamp.

wrenchman

Scorched air is never a better alternative replacement for a steam or hydronic system, in any situation. Hot air has no residual heat. When it's on it heats, when it's off it's cold. Hot air is only about the price, that's why it's a builders favorite.

RopeaGoat

Actually Steam can be a very efficient system. I'd suggest a thorough check of the boilers and controls, and the steamtraps and radiators before switching it out to scorched air. Also, the repair may be a pain in the buttocks but better done once and done right. The system probably got to this point by using ducttape and baling twine. We spent two weeks last summer replacing steamtraps in an older school/ community center here in Massachusetts and saved them ~$13000.00 this winter in fuel costs. Just my $.02.

thom

It is low pressure steam.

The leak that was exposed is near the top of a vertical pipe.

They tell me they saw steam emanating from the face of the stone retaining wall and from the earth below the retaining wall. This means more leaks. The leak in the vertical was far enough away that the steam from it was emanating from the ground above the retaining wall.

I did the quick screw patch. First with a #8 that just spun, then a #10 that spun, then a #12 that spun, finally a #14 that would snug up but I turned it softly.

I wrote them a letter that they will consider at the board meeting tonight explaining the problems.

The pipe is corroded on the outside. The screw I installed will not hold. I expect all the buried pipe needs replacing. This is a really large and hard hand-dig job. Probably 130' on two levels in unstable soil (sand and river stone). That gets the outside underground pipe but not the inside underground pipe.

Since I've never done any steam heat systems, I don't have a good idea about pricing but I'd guess about 150' of 2", probably 20 fittings, and then insulate it all for about several thousand dollars not including excavation and fill.

K2

Anyway to re-route new pipe without going underground and keep the proper pitch for steam?.. Also I've seen conversions from steam to hot water using the same boiler and alot of the existing pipe. Then at least you wouldn't have to worry about pitch. Boiler mods might cost but could be cheaper than the dirt work.

mdshunk

How rotten is this pipe? The reason I ask is this... do you think that you can pull in a new one with a pipe bursting head without doing that excavation?

thom

I doubt that anything would pull around an elbow. That's the toughest spot. The bottom of the vertical pipe that drops down behind the retaining wall. It's about 8' deep. That's a pretty large pit to dig in this soft sand with big rocks.

I'm unaware of anything that pulls through a 90. If there is something, let me know.

K2

This reminds me of a remod we did at one of the old electronics manufacturing plants from the 60's that used "chemicals". They wanted the underground waste pipe redone because of continuing problems getting worse. When we dug the mess up we found there was very little of the cast iron left, (eaten by the chemicals). Some places it was just a tunnel through the clayey soil, all the way out to the street main which had been replaced at some point in time.