First Steps When a Boiler Leaks
Before you work out where the water is coming from, make the boiler safe. If water is running rather than dripping, or it is coming from the boiler body rather than a pipe, flip the red emergency switch to Off. That stops the burner, and a burner that keeps firing on a boiler losing its water is the one way a leak becomes a cracked boiler.
Next, find the water feed valve on the cold line into the boiler, usually a small handle near a brass pressure-reducing valve, and close it. That stops the house's water supply from feeding the leak. Then move anything electrical off the wet floor and call. Those three steps take two minutes and keep a leak from turning into a flood or a dead boiler.
Boiler Leak Points, Most Common First
The Pressure Relief Valve
The relief valve is the brass valve with a lever on top of the boiler and a pipe running down toward the floor. It is designed to open at 30 psi and let water out so the boiler cannot over-pressurize. When it drips or spurts every time the boiler heats up, the system pressure is climbing too high.
The cause is almost always a waterlogged expansion tank. Water expands as it heats, and the expansion tank gives it somewhere to go. Once the tank's air cushion is gone, every heating cycle pushes the pressure past 30 psi and the relief valve does its job.
The fix is a new expansion tank, and if the relief valve has been dripping for weeks it gets replaced at the same visit, because a valve that has been weeping often no longer seals. The expansion tank repair and replacement page covers the symptoms in detail.
The Circulator Pump
The circulator bolts to the piping with two flanges and gaskets, and on older three-piece pumps the shaft has a seal. Both wear. A leak that shows up at the pump body or along the pipe below it is a flange gasket or a seal, which is a repair, or a pump that has rusted through, which is a replacement from the truck.
Fittings, Valves and the Drain
Threaded fittings weep as they age, valve stems lose their packing, and the boiler drain valve near the floor often drips after someone has used it. These are small jobs. Dry the area, run the boiler and watch where the first drop forms, because a drip from a high fitting can run along a pipe and appear somewhere else entirely.
The Domestic Coil Plate
Many Long Island oil boilers make the house's hot water through a tankless coil bolted into the side of the boiler. The plate that seals the coil to the boiler has a gasket, and when it fails water seeps out along the edge of the plate. A new gasket, or a new coil plate when the old one has corroded, stops it.
A Cracked Boiler Section
Cast iron boilers are built from sections, and a section can crack from age, from running dry, or from the thermal shock of cold water hitting a hot boiler. Steel boilers rust through. Water that appears from inside the jacket, or soot and rust streaks on the boiler itself, point here. This is the one cause that usually means replacement, and the technician will say so plainly with the repair price next to the replacement price.
Water Near the Boiler That Is Not a Boiler Leak
Plenty of calls about a leaking boiler end with a dry boiler and a wet floor from something else. Cold water pipes sweat in a humid Long Island basement in summer. A water heater standing next to the boiler can leak from its own relief valve or its tank. A basement window well or a foundation crack lets rain in after a storm, and it collects in the lowest spot, which is often right under the boiler.
Dry the floor completely, run the boiler through a heating cycle, and watch. Water that reappears while the boiler is hot and the pressure is up is the boiler's. Water that reappears on a rainy day, or on a hot humid one with the boiler off, is not.
Steam Boiler Leaks
A steam boiler, common in older houses on the North Shore and in parts of Nassau County, has its own leak points. The sight glass seals weep, the low water cutoff drains when it is blown down, and a steam boiler that has been overfilled pushes water out the relief valve. A steam boiler that needs water added every few days without a visible leak is losing it as steam through a leaking radiator valve or a bad vent somewhere in the house, and a technician traces that room by room.
Boiler Leak Repair Cost
The service call is $189 plus parts, with every part priced before it goes in. Relief valves, expansion tanks, circulator gaskets and coil plate gaskets are routine repairs, and the common ones ride on the truck so the leak is fixed on the first visit in most cases. The boiler repair page covers leaks, low water cutoffs and circulators in more detail.
When the boiler itself has cracked, you get a free estimate for a replacement alongside the repair option, and financing is available on a new boiler. The old boiler is removed as part of the job. Every price on the site is on the pricing page.
When a Leaking Boiler Is an Emergency
Call the same day, any hour, when water is running rather than dripping, when it is coming from the boiler body, when the pressure gauge is above 30 psi and the relief valve will not stop discharging, or when the leak has reached wiring, the burner or the oil line. Shut the burner off at the emergency switch first. The emergency heating repair page lists the other problems that cannot wait until morning.
Related Reading
- Why your oil burner keeps shutting off
- Common oil burner problems and what to check first
- How long an oil burner and boiler last
Boiler Leaking Right Now? Call Domino
Call (631) 867-2231 any time. A NORA-certified technician comes out the same day in most cases anywhere in Suffolk County, Nassau County or Queens, with the price quoted before the repair starts and no contract to sign.