At what point would it be impractical to dig up underground steam pipe?

nybigapple

Original post


I made that original post 4 years ago and today I received confirmation that the underground pipe is indeed the source of major leaking (approximately 1/2 a sight a glass a day). The insulation surrounding the steam pipe is completely flaking off this season and I've seen small billows of steam on the coldest days coming off the pipe through the exposed cement ends.

For reference, this is a 28 unit apartment "building". In actuality, it's two buildings separated by a courtyard. All the plumbing is handled in the cellar of the front building which holds 22 units. Pipes traverse the courtyard to the rear building for the other 6 units. For steam, this is done in what I believe are two counterflow steam pipes originally 2" in diameter but insulated within a larger pipe. The one coming directly off the main boiler header is the primary steam deliverer now and is the pipe I know is leaking. The second 2" pipe failed some years ago and they repaired by reducing to 1/2 inch copper pipe passed through the old pipe. The copper piping is large enough to still heat the apartments but the piping size is obviously inadequate to manage both steam and water well and has led to a slew of issues with built-up water and lots of water hammer to the point other pipes are beginning to get pinhole leaks and need replacing.

Back to the main question. The obvious answer would be to dig up the pipes and replace them. The issue is the leaking pipe is buried under 12 ft of cement and approximately 20 feet long. The second pipe with inadequate sized piping is under 8 ft of cement but approximately 24 feet long. I'm aware that we're not supposed to talk about pricing here, but I'm imagining an obscene cost associated with repairing this. We just replaced the steam boiler last year. John actually came by to take a look but passed due to the complexity and timing of the issue.

Would you guys agree the most practical solution would be to cap off both steam lines to the rear building, and then installing 6 ductless mini-splits? This solution would force me to have to pay the 6 tenant's electricity bills during the heating season but I am guessing it's still a tiny fraction of the extreme construction needed to repair.

leonz

Long, long, long, long before I would even consider doing what you propose with heat pumps I would get at least two estimates from horizontal directional drilling firms to replace the steam pipes by breaking the old pipes and slip lining in the new ones in their place.

This is ideal for your heating system especially if both ends of the pipes are exposed AND if not there would be much less excavation if needed.

With Horizontal Directional Drilling and pipe ramming you can break the old pipe and install casing pipes and and push in new pipe joints that simply lay in the casing pipe that is filled with insulating grout. I would do this long before installing heat pumps as your boilers are in good condition.

The term for this is trenchless pipe ramming.

There are many contractors that do this work with very small machines that work in small excavations at one end of the pipe run and push the pipe ramming tool through the old pipe and the expand the breaking tool, break the pipe, retract the pipe breaking wedge and advance the pipe ramming tool into the old pipe and repeat the process until the entire section of old pipe is broken and the new casing pipe and the steam pipe is installed behind the ramming tool.

It sounds complicated and scary "but I can assure you it is not complicated or scary" and it is very cost effective as you do not require a full length trench, trench boxes and replacement fill.

If there is room to work in your basements they can accomplish this work in the basement of your buildings without a pit for the power pack to break the old pipe and install a new casing pipe and the steam pipes.

There are a lot of directional drilling contractors with pipe rammers in your area.

Danny Scully

The most practical solution is to repair the steam, period, stop. So many questions though. For starts, 12 ft and 8ft deep of cement? What’s the story there. 

EdTheHeaterMan

Mini-split heat v. Steam heat

Is it possible to install a small steam boiler?

A small boiler could be placed in a room the size of a small closet. That could be a tiny addition to the outside of the building near where the pipes enter the building if there is no basement.

Many New Yorkers and Philadelphians (and many other cities) had to do this when the central steam plant closed down.

Jamie Hall

Both @EdTheHeaterMan and @leonz have excellent suggestions. You would be wise to price out both.

I doubt very much that six minisplits would be cost effective in comparison to either of those options -- never mind not being as satisfactory in terms of comfort.

I myself would prefer the horizontal drilling option. One does need some space -- a matter of a few feet -- clear where the pipes enter and exit the underground run. The longer the better, but only because then you need fewer joints of pipe when slipping the new pipe in.

leonz

Thank you Jamie!!!!!!!!!!!!!!!!

pecmsg

So what happened to the Money that should have been put away for this situation?

Bank Loan..................Do it right!

archibald tuttle

@pecmsg if the steam boiler was just replaced I would think that any sinking fund such as it might be has been exhausted. of course the reverse of belts and suspenders can happen and multiple capital maintenance issues can arise at once. But having had the city of Providence gobble my own sinking funds, because landlords are evil rich people who owe housing to everybody and if possible should be taxed and regulated out of existence (and then the folks doing this wonder why the price of housing is high), I'm quite sympathetic to this predicament.

And insofar as 'doing it right' is concerned I think a number of good ideas are on the table, including @nybigapple 's thought of possibly converting to mini-splits. As many discussions here have revealed, these are not ideal for comfort at the coldest temperatures in the region but they are getting better and as cynical as I am about making other utility customers pay for some of the cost, in targeted difficult situations they can be a lifesaver for a property owner.

Obviously, if they are backed up by resistance heat and you are paying the electric bill this could be difficult but in transition you could modify leases to reflect the change, although if you use locked thermostats of some sort and try to maintain tenant relations while controlling costs could work, esp. if the air conditioning adjunct of such a system would be attractive it still might overall be worth considering so I wouldn't write it off although many other ideas are good.

In the NFN department. I'm on same page with the 12 or 8 feet of concrete question with @Danny Scully , but maybe you don't mean it is solid but that there is concrete surface of whatever 6" a foot or perhaps little more or was it literally filled with concrete over the excavation to that depth? What I don't see as an alternative is whether it would be possible to service with a near surface excavation (perhaps still more expensive than horizontal drilling depended on space to work) or even overground piping. I'd just think of it as a long high header before a drop which goes to the question of whether the replacement 1/2" copper pipe is, I presume, a wet return? Or is it literally carrying counterflow to half the units. That seems almost impossible but I guess anything is possible in a pinch.

Also I wonder whether there are lesser than full bore solutions for augering treatment. Hard to believe although maybe with heaves and corrosion that they couldn't get a little bigger pipe through the 2" but 20 or 24 feet can be daunting. But wouldn't put it past myself to try and aggressive rooter machine and spade cutter as a first go. Because if you could get it open for say 1 and 1/4" copper you'd be way better off than you are now.

It may strike you correctly that I think of things I would try myself. If you are hiring professionals then you are paying their professional hours to go down a potentially unproductive track. But even then if you are at the end of life then you gonna have to buy some electric heaters for these folks and check their wiring and circuits to support them while we are still kind of in should season and as soon as you cut off that 2" steam pipe if you have rooter guy you could ask him to see what he could do as a modest cost experiment.

Or Near surface you could do with a very small machine and a saw depending on the thickness. or , if the courtyard is enclosed on one end and any doors in that end are high enough off the ground could you run insulated pipes with any digging with a return a foot or so below the feed catching the drop condensate. This might orphan below grade flats if you have them but that would reduce the number of units that might need alternative treatment.

Or, if this is a two pipe system to the rads, what about converting the back building rads to hydronic, smaller insulated overground or shallow burial of service? I am running several combined steam and hydronic systems. It's not a bad fit. You can fill the system and then pump out of the boiler with check valve. Might be a little dicey in practice if the replacement boiler has smaller water capacity although in theory that wouldn't be an impediment. But I have also handled this load with a heat exchanger buffer tank (usually made from DHW tank out of service but whatever I can get my hands on).

The only issue I see with @EdTheHeaterMan 's suggestion to install a steam boiler adjacent to or in mechanicals area of back building is access to gas line, more excavation? the level at which steam service is needed and whether the boiler can be placed low enough and of course with rad style heat , steam or hydronic, you're talking flu temps that exceed most convenient sidewall venting solutions although not all of them, if there is not a quality chimney with flu available in back building.

Nothing is cheap but maybe something is reasonable.

Jamie Hall

I too am puzzled by one aspect of your description, @nybigapple . You say "the leaking pipe is buried under 12 ft of cement " and the other under 8 feet... really? Not that it changes my recommendation -- it doesn't -- but I have to admit that I find it a little hard to envision -- even in New York City -- a situation where one would be faced with an 8 foot -- never mind 12 foot -- thick slab (well, block) of concrete...

nybigapple

I'll post a video for the group a little later when I can. There is a sub-basement apartment and a cellar which is the base of 8 feet. The leaking pipe has a walkway built over it for an additional 4 feet. I'm fairly positive it is solid cement. The design is very unusual even for nyc which is why FDNY will often stop by just to show the building off to explain special building designs. I was told they only know of two in Manhattan like it, with two buildings separated on the same property.

When John from Gateway stopped by last year I actually inquired about installing a second small boiler just for the rear building as I really liked that idea. The difficulty is that you would need to install a flue, which is again very costly as well as difficult in getting NYC to approve another boiler.

I like the idea of trenchless pipe ramming, but I'm guessing there is no space to work. It really is a tight space and they must have planned for there never to be any issues with the pipe with the cement that deep.

The 1/2 inch piping is definitely a dry return well over the boiler line. It "works" but as you can imagine there is an extreme hammering in the risers and the water backs up to the point you can hear water in the last riser. The radiators on that riser don't actually even get steam on busy boiler days due to the flood of water that the steam can't get past and the heat comes from the boiling hot exposed riser.

This is a 1 pipe steam system so the idea of converting to hydronic isn't really possible without more construction.

As for the comment about money and "doing it right", this is a tenement, rent stabilized property and the bare minimum was done to maintain it for many years. Nobody was getting rich here. In the last four years, I've replaced the hot water storage tanks, the boiler, and installed a new flue. As you can imagine there are also many issues with the building that are not plumbing related that I still have to consider as well.

Jamie Hall

Well, that's a little clearer anyway.

On the 1/2 inch pipe which is a "dry return" on a one pipe system. That pipe, I take it, isn't leaking? It's sound? Can you pressure test it? Will it take 30 psi?

OK. Let's assume for 10 seconds that it will. That problem is easily solved: you put (much as I hate them!) a vented condensate receiver in the distant building and a float controlled pump on it. Connect what now goes into that pipe in the distant building into the receiver, connect the pump to the existing pipe, and you're done. You may need a steam trap on the riser or risers going into it; you could use F&Ts for that. You might just get away with thermostatics -- I'd have to look at the piping. You might not need them at all, if the elevations are right to create a water seal. Conceivably you might need a boiler feed buffer tank and pump by the boiler.

That leaves the steam main which is probably too small anyway, and is leaking. Is there any good reason why that can't be routed through the subbasement apartment and cellar? If it's properly dripped a steam main can go up and down, never mind around corners. You might have to core drill through a foundation wall at one or both ends, but that's no big deal.

Odds are that the tenant of the subbasement apartment might have a fit -- briefly -- but not if you do a neat job, and certainly not if the place is rent controlled.

And all of that is going to be much less expensive than any of the other options we've been looking at.

archibald tuttle

@Jamie Hall are you suggesting a condensate receiver and then occasionally pump the condensate through the 1/2" pipe well overcoming steam pressure and quickly emptying the receiver but otherwise let that 1/2" it be a steam 'main'?

I can't quite envision from @nybigapple 's description of the 1/2" as a dry return whether the leaking 2" feeds the entire building and pitch or relative A/B if you will of the two pipes makes the 1/2" a return or if they were both intially counterflow aimed at two different 'trees' in the adajacent building.

does the subterranean apartment then run across the end of the courtyard and could you employ jamie's suggestion to route steam to the adjacent 6 apartments through there and/or what about just an insulated run above ground high enough to allow for a trapped return for that main. are their at ground level windows for the basement that would be obscured. could you run the feed just above those basement windows and the return around the sill with a bit of pitch or pumped as @Jamie Hall suggests in which case the pitch of the return is less critical?

Jamie Hall

I'm not sure I quite envision what's going on, either, @archibald tuttle ! But I'm suggesting turning that half inch pipe (whoever thought that would do anything by gravity?) into a pumped condensate return, and using the 2 inch pipe as the steam feed -- with whatever repiping is needed on the other end to get the steam to the risers and get the condensate back to the tank. The half inch on the boiler end would feed into the wet return -- or into a boiler feed tank, if need be. Might need a check valve in there somewhere, depending on pressures.

Perhaps the OP can clarify all this for us...

nybigapple

I was mistaken about the size of the smaller pipe. Does it look like maybe 1 inch? Here's the video of the situation. It is very rough.

https://youtu.be/hIhr5yG8zLE

leonz

Now that I know more about this I can tell you the small pipe ramming systems will fit in doorways and and very work well in cramped areas.

Moving the tenant out for a day and protecting thier furniture for day or two with high quality tarpaulins would be all you would need to do to do the work of breaking the old pipe and pushing in the new casing.

After that the steam pipe can be set on the proper grade once you have a line of sight in the piping to do the setting of the pipe in the casing pipe with grout and the proper elevations from A to B in both cases.

Using a casing pipe will protect the new steam pipe and the grout will hold in the heat.

Worse comes to worse you could use welded pipe joints in small lengths.

But if the basement apartment is open and has a long passage/clear shot in a passage through a window you could lower an entire pipe length in the apartment and then ram the lengths of casing pipe in and finish the job wit the steam pipe using one length of welded or threaded pipe joints.

DONT LOSE HOPE, find a plumber that knows someone that has a directional drilling business and your halfway there.

EBEBRATT-Ed

There"s nothing stopping you from running it all above ground either

nybigapple

The steam pipes don't actually go through apartments. They go directly from cellar to cellar. I was thinking there wouldn't be enough room to use any major machinery. The leaking pipe I showed you I'm sure isn't enough to work. You're talking a width of maybe 3 ft. The height of that ceiling is also an annoying 5'7" maybe.

nybigapple

EBEBRATT-Ed said:

There"s nothing stopping you from running it all above ground either

How would the above-ground piping work when the elevation difference is so high? I'm having trouble picturing it.

archibald tuttle

EBEBRATT-Ed said:

There"s nothing stopping you from running it all above ground either

my point exactly. looks like a down stairway to be gone under at the end of courtyard if i'm interpreting video correctly. i'd say, screw burial and go overland.

PS that 1" which drops I expect from the video is a condensate return. pumped could improve the hammering but really not that bad compared to the 1/2" you intially thought you were dealing with. so the header drops to the leaking feed with a return to the boiler just prior to going through the wall by the stairs. and all of that is 8 feet below the surface from your video and dicta. but I don't see why the steam feed couldn't go up the 8 feet and cross the yard. you would probably have to drill under the stair way that has the bikes parked next to it but that is an even more discrete task.

and BTW, I don't buy that it is solid concrete down to the pipes, except where the stairs and retaining walls descend. still not an easy or rational excavation but i don't think you have to replace at the same elevation.

EBEBRATT-Ed

We had a hospital just north of me here 40 years ago that the underground fuel oil tanks were ok but the oil lines between the underground tank and the building had failed.

We went to a welding shop and had them make us some pipe supports which consisted of 2" pipe with a piece of channel iron on top of it welded to make a "tee" . The pipes were pounded into the ground with the horizontal chanell on top and set them at the same elevation about 8' apart from the building to the oil tank manhole. We installed steam condensate return for the tanks oil heater and new supply and return fuel oil lines. Everything got insulated and they had carpenters build a box around the piping and planted bushes on either side to conceal it. Ran that way for many years until they replaced their underground tanks. It was at least a 50 ' run

Jamie Hall

Even 1 inch -- and it does look bigger -- is useless for carrying any amount of steam any distance, especially if it's countercurrent. I really do think you will be much happier repurposing that as a dedicated return from a condensate receiver and doing whatever repiping is necessary at the other end...

archibald tuttle

and i'm assuming if you attribute a half a site glass a day to this problem that you don't have an autofeed?

nybigapple

There is a 101a autofeeder, but I've turned it off as the LWCO started flooding the boiler(needs cleaning) and have been manual feeding. That allowed me to monitor the water use the last few days intently. I'd estimate around 4" every 24 hours.

JUGHNE

I would suggest the overhead elevated new steam lines.
The main would have to slope either up or down with a drip on the ends.

Some years there was a lengthy discussion about a steam system in of all places San Francisco. The boiler was moved to a building in the back yard and the piping run to the apt bldg.
It had issues with the piping in the apt, but not the overhead piping. You would need much more insulation then they had there.

There is steel round ducting, maybe "Spiral Duct" or such that is very rigid, could be rated for outside use with painting and proper supports. There looks to be no vehicle traffic to go under it??

On the other hand, it looks like the concrete pour is typical thickness between the stairwells. You could saw the concrete, jack hammer, small back hoe for a trench. Install something like the underground ductwork mentioned above. (Where I live in the boonies, common sense would allow 6-8" sch 40 PVC pipe sleeves). Highly insulated steam and return pipes slid inside.
You may need the condensate transfer pump in the back building, if so the 1" you have would probably suffice. Although I would put new in with the steam main for whichever route you go.

Above or below choices may be dictated by your fine NYC permit department. I can only imagine what cluster that might ensue.
UG should be no more complicated than burying a sewer line.

archibald tuttle

Jamie Hall said:

Even 1 inch -- and it does look bigger -- is useless for carrying any amount of steam any distance, especially if it's countercurrent. I really do think you will be much happier repurposing that as a dedicated return from a condensate receiver and doing whatever repiping is necessary at the other end...

from the video, i think that copper is already configured as maybe a common flow return (although we don't see the end of that in the auxiliary building). because it seems to be running at a relatively similar elevation to the leaking steel pipe, maybe even a little higher but it's hard to gauge which would cut against the return theory. there is a vent butI'm pretty sure if I followed the video correctly that that vent is to let steam back around from the other building so it wouldn't be a contra flow pipe albeit that is a guess because the pipe in the supply building is so low. I guess maybe the steam could drop down but that sure looks like a return to me. and the copper drops maybe 4 or 5 feet with no connection at a higher steam delivery level from the boiler so i think it is maybe already a return or common directional flow pipe in any event.

have i been drinking too much (it's possible).

nybigapple

Here's a video of the piping in the cellar of the rear building. It is not piped well as there are pitch issues.

https://sendvid.com/ubjlbjij

archibald tuttle

@JUGHNE

agree. suspect the same thing about modest concrete thickness and then a little insulated exposure at the stairways.

JUGHNE

Do you have other piping runs between the building...hot - cold etc?
If so and you go for the UG trench, I would put in additional sleeves for future pipe upgrade. One trench and get it all done.

leonz

nybigapple said:

The steam pipes don't actually go through apartments. They go directly from cellar to cellar. I was thinking there wouldn't be enough room to use any major machinery. The leaking pipe I showed you I'm sure isn't enough to work. You're talking a width of maybe 3 ft. The height of that ceiling is also an annoying 5'7" maybe.

=====================================================
If you have room to go through a door you can use pipe ramming and HDD drilling machinery with pipe bursters that can be used in basements with no issue as they make them small too.

Call a plumber and ask who he knows that has pipe bursting equipment and get a quote for all the work before you do anything.

Jamie Hall

The only issue you would run into would be jointing the pipe. The machinery, as @leonz says, will fit.

You note that the width is only 3 feet. What is the distance to the nearest obstacle on a line with the pipe? If you're actually down in a 3 foot square pit, it's going to be tedious... but doable. I would strongly suggest, due to the number of joints if you are limited to 3 feet, that you use steel pipe and engage a competent welder to make up the joints as you feed it through.

Just for a reference, I personally engineered and supervised the replacement of 1500 feet of 24 inch concrete sanitary sewer -- under a river and active railroad line -- using directional drilling from two pits, each only 8 feet square (one pit for the drilling machinery, one for the installation hauling winches). Piece of cake? Pretty much, though there were some odd moments...

nybigapple

Thanks for all the advice. I'm going to contact a few people about the trenchless drilling and look into doing it after heating season ends.

leonz

As I said you need a plumber and a driller with a doorway sized portable HDD rig that can burst all that old pipe and drive a casing pipe for both lines to enable you install the new steam pipe.

As Jamie said welding the pipe joints is best, preferably with a small robotic pipe wire welder that would clamp on both sides of the pipe joint and rotate around the pipe while welding it which would be the best and fastest way to do this.

The pipe joints have to be beveled and pipe joint sleeve inserts used to fill in the base metal gap with compatable metal to wire weld and fill the joint to the proper thickness to pass steam code inspection.

This is the most effective and quick way to pass the code inspection for insurance approval for the steam piping.

You do not have the room to use a low speed pipe rotator to use a hand held stick welder or mig wire welder in this case to make the pipe joints.

Do not expect to do this inexpensively and quickly as there is a lot of preparation to do this work that has to be done.

A plumbing inspector is not your friend right now........................

PerryHolzman

I also agree with the pipe ramming and installing a new sleeve pipe.

As for the steam pipe... Is there a room on the other side of the wall? In power plants we have often core drilled a hole in a wall to allow us to feed a longer pipe from an adjacent room into an underground sleeve pipe (you might do the same with the sleeve pipe). That minimizes the welds (and power plants have very experienced certified pressure pipe welders that pass all code inspections).

I wish you the best with this.

Perry

archibald tuttle

all this talk of pipe ramming and welding has the dollar signs spinning. i still like overground but what about trying to put a roto rooter through the existing. if you can get a 1 " spade through then get a bigger spade and if you could get something on the order of 1 and 3/4 inches through with the roto rooter maybe you have enough back throw if you cut the drop from the header and let it bend below the flue pipe to get a 20' piece of 1 and 1/2" copper maybe through there which might almost reach from the exposed pipe in the stairs on one side to the expose pipe in the scuttle stairs under the trap door on the other side. or if you're not so luck 1 and 1/4" ?. . . . I'm impressed they got 1" through the other one maybe with just physical determination . . . I mean I'm saying.

EBEBRATT-Ed

@archibald tuttle

Your right about the $$$$ of pipe ramming and welding.

leonz

By ramming the hydraulic breaking head in the existing pipe and
breaking the existing pipe the follower pipe being the larger casing pipe is inserted behind it and there is no chance of collapse of the ground in the pipes path where trying to use a rooting tool and coil spring steel extension joints or rods will or could be trapped and become un retrievable due to the fill dirt used.

Like the old purolator commercials said;

"You can pay me now or pay me later"

It is now later I guess.

We have not been told whether the plumbers that put the new steam boilers in discussed the condition of the pipes with this fellow if he was the property owner when the boiler was installed.

nybigapple

@PerryHolzman Unfortunately no... On the other side of the wall next to boiler room steam pipe would be the neighboring building's exterior wall. The wall you see in my video is the foundation wall. It's one of the reasons I wasn't sure if there was enough room. The rear building has more space to work with than the front by a foot or more width wise. But the steam pipe is still only a few inches from the wall.

I'll look into all of this when I can. But if it's truly as expensive as you guys are implying I may just go over the top like archibald mentioned. I need to find competent people for both and price it out.

@leonz yes we were also the owner, but at the time it was more pertinent people got heat, period, the end since we were forced to do an emergency install due to a leaking boiler after heating season started. I believe the water loss hasn't gotten worse between last year and this one. I estimated 4 inches but now that the weather has gotten colder it's significantly more than that. I'll have to bear with it till the weather gets warm again.

archibald tuttle

nybigapple said:

I'll have to bear with it till the weather gets warm again.

in the NFN department and as a shameless thread jack, I just started a thread wondering whether installation of a sacrificial annode is appropriate in a system with high make up or bleedwater changeover.

the thread says hydronic, but i added a paranthetical caveat for steam as there is a thread running right now on a less complicated steam leak scenario where the extent of makeup water is seen as an issue that could threaten the boiler, and you have just had your boiler replaced.