Boiler Repair & Maintenance
Radiators, baseboard and radiant floors need someone who knows hot-water heat. Boiler repair and yearly maintenance from MoJo, for homes across Denver.
Boiler heat is quiet, even and comfortable, which is why so many owners keep their systems running for decades. When something does go wrong, the fix takes someone who understands hot-water heating, not only forced air. MoJo Home Services handles boiler repair and yearly upkeep for homes across the Denver metro, on everything from cast-iron radiators to radiant floor loops.
Two Kinds of Boiler Homes
Hydronic heat turns up in two very different kinds of houses. Many older homes in Denver's established neighborhoods still run cast-iron boilers that feed radiators or baseboard. Some newer custom homes have radiant tubing in the floors and a high-efficiency condensing boiler in the mechanical room. The two setups age differently, and we work on both: the boiler itself, the pumps and valves that move the water, and the controls that tell each zone when to run.
Symptoms Worth a Call
Cold radiators or baseboards, often upstairs or at the end of a loop, which usually means trapped air or a failing circulator pump.
Pressure out of range. A gauge that keeps dropping points to a leak or a faulty fill valve. One that climbs until the relief valve drips points to a waterlogged expansion tank.
Kettling or banging, a rumbling sound caused by scale or sludge overheating water inside the heat exchanger.
Water around the boiler, at pump flanges, valves or old fittings.
Short cycling or ignition lockouts, where the burner fires briefly, shuts down or shows a fault code.
One zone that won't heat while the rest of the house is fine, which often traces back to a zone valve or its thermostat wiring.
Three Things to Note First
When the heat acts up, jot down the reading on the pressure gauge, whether the relief valve or any fitting is dripping, and whether one zone or the whole house is cold. Mention those readings when you book a boiler visit, through our Wheat Ridge office, and the technician can bring the likely parts. Also confirm the boiler's power switch, often a red switch near the basement stairs, has not been turned off by accident. If the pressure is far below where it normally sits, leave the system off rather than refilling it yourself.
What We Check on a Repair Call
We begin at the pressure and temperature gauge and the burner's lockout history, then work outward through the system: circulator pumps, expansion tank charge, pressure relief valve, automatic fill valve, air separator and each zone valve and zone control. On radiant floor systems we also look at the mixing valve that keeps floor water at a safe, comfortable temperature. Combustion and venting are checked on every gas boiler, with the burner adjusted for Denver's altitude. If part of the house runs on a furnace or heat pump instead, that equipment falls under our general heating repair service.
Yearly Upkeep That Heads Off Breakdowns
A boiler that gets attention once a year tends to give many years of quiet service. Annual boiler maintenance from MoJo includes cleaning the burner and inspecting the heat exchanger, testing the relief valve and safety controls, checking the expansion tank, looking for leaks and corrosion, confirming the venting is sound and running a combustion check. On condensing boilers we also clean the condensate trap and check the neutralizer. Systems that use glycol antifreeze, common in radiant loops that run under garages or outdoor slabs, need the fluid tested too, because old glycol turns acidic and attacks pumps and fittings. Early fall is the right time, before the system starts running every day.
Keeping an Older Boiler or Starting Over
A well-kept cast-iron boiler often outlasts a furnace by many years, so age alone is rarely the reason to replace one. A leaking or cracked heat exchanger, repeated failures of major parts, or gas use that keeps climbing are better signals. When replacement is on the table, we explain the options, including high-efficiency condensing boilers, and what each would mean for your radiators or floors. A replacement is also the moment to fix long-standing annoyances, such as a zone that never quite warms up or a pump that runs all day, by rebalancing the loops or adding outdoor reset control, which lowers the water temperature on mild days and raises it when the weather turns.
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Help Center
Frequently Asked Questions: Boiler Repair & Maintenance in Denver, CO
Why does my boiler keep losing pressure?
A small leak somewhere in the piping, a relief valve that weeps, an expansion tank that has lost its air charge or a fill valve that is not doing its job are the usual causes. Many homes run somewhere around 12 to 15 psi when the system is cold, though the right figure depends on how tall the house is. If you have to keep topping it up, have it checked before the low pressure causes a lockout.
Do radiators need to be bled?
If a radiator is warm at the bottom and cold at the top, trapped air is the likely cause and bleeding it will help. Many newer systems have automatic air vents, but older radiators still have small bleed valves. If the same radiators keep collecting air, the system may be drawing it in through a leak or a failing vent.
Is a kettling boiler dangerous?
Kettling is the rumbling sound of water boiling in spots inside a scaled-up heat exchanger. It is not usually an immediate danger, but it wastes fuel and stresses the boiler. If the pressure keeps rising or the relief valve starts discharging, turn the boiler off and call for service.
Can you service radiant floors and baseboard systems?
Yes. We work on the whole hydronic system, including radiant floor manifolds and mixing valves, baseboard and cast-iron radiators, circulator pumps and zone valves, along with the boiler that heats it all.
Does Denver's altitude affect a boiler?
Gas boilers at this elevation are derated like any other burner, so combustion needs to be set up for the altitude. Condensing boilers also depend on cool return water to run at their rated efficiency, so the controls and water temperatures matter as much as the boiler itself.
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