Steam heating boiler leaks can occur at any of a number of locations, any of which should be repaired promptly.

This article describes a cast iron steam boiler that was destroyed by prolonged leaks, some of which were hidden from view. Were these wet spots simply vintage patina on a mature boiler or was there a pending disaster?

Prolonged Leaks Destroy Vintage Steam Boiler

At the steam boiler shown here, the homeowner found continuous dripping at the back of the boiler where the condensate return piping enters the boiler bottom.

This steam boiler, probably installed in the 1980s, suffered multiple leaks at an abandoned tankless coil and at the condensate return tapping on the bottom back of the boiler. Like many like-minded people, the homeowner was of a mind to defer this costly boiler replacement job for as long as possible.

Photos: water on the floor around a boiler merits prompt investigation. A leak might be from a dripping or recently-opened valve, or it may be more serious, as were several leaks found at this Weil McLain steam boiler. The heating service technician confirmed that this boiler was not repairable.

Watch out: This boiler was leaking in several places, worst from its condensate return tapping at the boiler bottom-back. But if a leak at your boiler is from a temperature/pressure relief valve that can be a serious safety concern.

See RELIEF VALVE LEAKS for details.

Eventually on this boiler rust became so severe that the boiler leaked water fast enough that the homeowner noticed water on the floor. "Living with" that leaky boiler might have led to its complete failure, but in fact by the time these leaks were obvious and continuous the boiler had probably been beyond repair for some time. And as we illustrate here, small boiler leaks can be hard to spot.

Why? Because small water leaks on any water or steam boiler body or at piping connections onto the boiler itself will seep out onto a usually very hot boiler surface where the water quickly evaporates. By the time boiler leaks are so advanced that the homeowner notices them as water on the floor, the boiler's condition may already be beyond repair.

It would have been better to replace this boiler over the summer months when the leak was first observed. That approach would avoid the possibility of a loss of heat during cold weather, and it would allow the heating company workers to replace the boiler during a less-busy moment in the heating season.

Our OPINION is that the greatest risk of boiler total failure from leak damage occurs when the building heater is needed most: during the coldest weather when the boiler is working hardest, with longest run cycles.

Watch out: don't leave leaks un-repaired at your steam heating boiler. Even a cast iron boiler like the one shown in these photographs can be destroyed by severe rust that accompanies protracted leaking. Besides the risk of a building flood from a burst boiler, waiting until a boiler is in such bad shape that the heating service technician insists on leaving it turned off means that you may have to leave your building with no heat for several days when outdoor temperatures are near zero.

The heating service technician inspected the under-side of this cast-iron Weil McLain steam boiler before expressing, in rather direct terms that we won't repeat here, that the boiler was beyond saving.

Visual inspection alone was enough to confirm that the coupling and piping at the back of this cast iron boiler were leaking badly and were beyond repair.

Watch out: never poke or "pick-at" thick rusted corrosion on a heating boiler: the risk is that you convert a slow drip to a much faster leak, creating an immediate emergency or a building flood or both.

Other leaks were obvious to the naked eye: leaks around an abandoned tankless coil on the boiler's upper side.

Noticing that there was also leakage at the fittings around the steam boiler's low pressure control, and notwithstanding that normally a residential steam system operates at below 0.5 psi pressure, the tech flipped off the boiler's power switch.

Above: yellow arrow points to a small leak at piping feeding the steam boiler's pressure gauge and pressure control. The service technician's view was that leaks at these locations could prevent the pressure control, a steam boiler safety device, from properly-sensing the boiler's pressure.

"This boiler is too dangerous to run," he opined. "I've turned it off. Don't turn it back on."

The homeowner had known that the boiler was leaking, and previous service technicians had noted that on the boiler's service tags. Remarkably, a section of leaky condensate return piping had been replaced and connected to the nipple at the boiler's back (orange arrows in the photo below).

We were impressed that the tech was able to connect new piping to the old corroded fittings at the boiler without precipitating a leak at the back of the boiler (yellow arrows). Or maybe not.

Our OPINION is that should an attempted repair such as that shown in the photo below result in a leak at the connection of the condensate return fitting in the boiler itself, rendering further repair impossible in this case, the leak is not the fault of the servicing technician.

Rather the work disclosed an imminent failure of the boiler. Unfortunately, heating service techs know that a homeowner may take a different, if incorrect, view.

By the time the leaks became rapid, the condensate return line tapping on the boiler was so rusted that the fittings could not be replaced.

In fact when the heating company removed the boiler in order to install its replacement, the condensate line could not be un-screwed, but it could simply be broken away from the boiler by hand. (Red arrow, photo above)

In fact there were other severe leaks higher on the boiler that would not have been obvious until the boiler's rusting steel jackets were removed. Seeing rust coming through a boiler's steel jackets is always worth investigating.

When the old cast iron boiler was wheeled out of the home in preparation for its replacement (photo above), its jackets were off and one could see serious leak damage that was otherwise hidden behind the insulated steel boiler jacket.

With the leaky steam boiler's covering jackets removed, we could see extreme exfoliating rust not only at the bottom of the boiler's condensate return opening, but high on the boiler, between boiler sections.

Remarkably the steel rod intended to bolt the boiler sections together had rusted through and was broken (vertical yellow arrow in our photo below). Only luck and surrounding piping on the unit had kept this boiler from simply falling apart on the floor.

At their upper end, the cast iron boiler sections themselves were rusted nearly through. When you see thick flakes of metal disintegrating that's exfoliating rust - not simple harmless surface rust.

At any moment this boiler could literally have fallen apart.

How might we suspect hidden leaks on a heating boiler? By increased water usage above normal. If a steam boiler is leaking its automatic water feeder will be sending an increased quantity of water into the boiler. Because water is being added by the water feed valve, the boiler's safety control,

its LOW WATER CUTOFF VALVE , won't operate to turn off the boiler unless the LWCO stops working or the leak becomes so fast that boiler runs out of the boiler faster than the water feeder can add its replacement: a condition likely to flood the building with water.

See also WATER FEEDER VALVE, STEAM.

Above: the replacement boiler being brought into the home, and below, the new Peerless PB replacement steam boiler with installation nearing completion.

Watch out: at CONDENSATE RETURN PIPES, PUMPS, STEAM we explain that a leaky condensate line such as the one shown here can be lead to

dangerous BLEVE EXPLOSIONS.

...

Continue reading at LOW WATER CUTOFF VALVE or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see STEAM HEATING SYSTEMS & CONTROLS FAQs - questions & answers about steam heating system repairs posted originally on this page

Or see these

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STEAM BOILER LEAK DAMAGE at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to STEAM BOILERS

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