This one goes back a bunch of years. The contractor was a good steam man, but he had run out of ideas with this job. It was a typical, five-story, New York City tenement building. Its one-pipe steam system had served generations of tenants for more than 100 years.

“This one riser that takes care of the back bedroom on each floor just stopped heating,” the contractor told me.

“What changed?” I asked.

“Beats me. I asked the people in the building, and they said nobody else had touched the system. Just me. And it was fine the last time I was there.”

“Well, something changed.”

“Yes, the riser stopped heating. But why?”

“What have you done so far?” I asked.

“I changed all the air vents, as well as the main vent down in the basement. I checked the pitch of all the radiators on that riser. They all pitch backward toward the supply valve. I don’t think the condensate has any problem draining from those radiators. I also opened and closed all the radiator supply valves. They’re old but they’re turning. I don’t know what else to do. What could suddenly shut down an entire riser?”

Problem solving with gravity

I love a good challenge, so I met him on the job. And since we didn’t know what was causing the problem, I suggested we look at everything.

We walked around the basement and climbed the stairs to look in all of the apartments served by that riser. All the radiators in each apartment, except for those on that one line, were heating as they should.

We went downstairs and checked out the boiler. It was the right size for the connected radiation, and it had heated the whole building up until that riser decided to quit. The steam pressure cut-in at 1/2-psi and cut-out at 1 1/2 psi, which was right for this system. A too-high pressure in a one-pipe steam system can hold air vents closed, particularly those set to vent quickly. That can lead to no heat beyond the first cycle. But that wasn’t the problem here. It was just that one riser.

We walked around the building some more. Years ago, the installing contractor had anchored the steam risers at their midway point. I knew this because I saw the screwed escutcheons around the risers on the ceiling of the second floor and the floor of the third floor. Anchoring them like that kept each riser from expanding straight upward from the basement toward the fifth-floor radiator. That much expansion can cause the top-floor radiators to pitch toward the air vent and squirt water. With the anchor point in the middle, the riser will expand both upward and downward against the swing joint in the basement. It’s an old-timer trick, and I pointed it out to the contractor. He had never noticed that detail.

So what’s inside? You never can tell, but it’s always a great question to ask when you’re troubleshooting.

“It’s in the old books,” I said.

“I need to read more.”

“The drawings in those books are the best,” I said. “I never would have thought of that detail on my own. I’ve seen jobs where they removed those anchors and then had to deal with the squirting vents up on the top floor.”

“Good to know,” he said.

And that got me thinking about those fifth-floor radiators, so we paid the problem riser another visit. And this time, at its top.

I opened and closed the radiator’s supply valve. It moved as it should, but then I wondered what it was like inside.

“Can you pop the bonnet?” I said.

“I’ll try,” he said. “What are you thinking?”

“I want to see if the valve seat is still attached to the valve stem,” I said.

He opened the bonnet and took it out. The stem was there but the seat was missing.

“What the heck happened to it?” the contractor asked.

“I’ll bet it’s in the basement,” I said.

We went downstairs and found the base of the problem riser. We looked at each other. He shook his head and sighed.

“Yeah,” I said.

“I’ll get the saw.”

“Some days are better than others,” I said.

“If we solve this, I’m not going to complain about the work,” he said.

He cut the riser at the elbow where it turned upward. Sure enough, the seat from the radiator valve up there on the fifth floor had fallen into that elbow and clogged the pipe just enough so that the steam couldn’t get by.

“It’s acting like a throttled valve,” he said.

“Yes.”

“How did you know to look here?” he said.

“The top-floor radiator is the only one that has a supply valve connected directly to the top of the riser. There’s no swing joint there, so the seat was able to fall five stories and get stuck right at the bottom in the runout from the horizontal main to the riser. I just had a feeling,” I said.

“Was that in the old books?”

“No,” I said. “But I kept thinking about where I would go if I broke off from a valve stem. You can’t get away from gravity, can you?”

“Not on this planet,” he laughed.

It took a bit of work to get the pipe back together, but when he was done, that riser heated beautifully.

“What do I owe you?” he said.

“I’ll take this fine story as payment. Thanks.”

Troubleshooting hot water

Another day, another job. This one was hot water. One of the zones was erratic. It would get hot and then go cold. The circulator was running and the contractor had purged it again and again without it making a difference (why do we do that?)

“It’s almost like someone is opening and closing a valve,” the contractor said.

So we looked some more and we did our best to think like water. The pipe got hot to an elbow and went cold at that point, but not all the time. I was thinking the fitting was partially or fully blocked. That’s a manufacturing defect. It’s unusual and I’ve seen it in cast fittings, but never with a copper fitting, which this one was. But when you don’t know what’s causing the problem, you can’t dismiss any possibility, so I asked the contractor to cut the pipe so we could look inside that elbow.

You know what was in there?

A nickel. And sometimes it was turned this way, and other times it was turned that way. Just like a butterfly valve. Flow. No flow. Flow. No flow.

So what’s inside? You never can tell, but it’s always a great question to ask when you’re troubleshooting.

Other internal complications

Another guy told me he once found a roofing nail in the inlet flange of a Bell & Gossett series 100 circulator. The circulator was on the vertical return line from the system. There was no flow because the nail was acting like a check valve installed backward. The nail would allow water to pass backwards up the return, but not downward into the pump. Gravity caused the nail to drop into place and stop the flow again and again.

Oh, gravity.

And speaking of B&G; I worked for their rep years ago. We had this shell-and-tube heat exchanger that wouldn’t do what we promised it would do. We popped the head open and found a pair of welding gloves pressed up against the tube sheet with fingers splayed. Seriously.

Or how about this one? The boiler was making a rumbling sound. At first, the contractor thought it was the circulator, so he opened it up and it looked fine. The rumbling continued and it was definitely coming from inside the boiler. He tore down the boiler and found a few hundred acorns rattling around in there.

Squirrels. Try finding that solution in a textbook.

Another contractor friend found a live baby owl in the flue of a cold-start boiler. The homeowner had jammed the barometric damper shut because he thought it was a squirrel making the noise (not guilty this time). He called the contractor and the contractor called animal control. They got the baby owl out alive and released it in the woods.

You never can tell what’s inside. And sometimes, it’s a real hoot.

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