If you live in one of Delaware County’s older twins, rowhomes, or stone farmhouses, there’s a good chance you’re not dealing with a furnace when the heat dies. You’re dealing with a boiler, and that’s a different animal with its own set of symptoms, noises, and failure points. Here’s how to figure out what’s actually wrong before you decide whether to grab a wrench or pick up the phone.
Why So Many Delco Homes Still Run on Boilers
Walk through Chester, Upper Darby, Media, or any of the pre-1950s neighborhoods in the county and you’ll find block after block of twins and rowhomes built with cast-iron radiators and a boiler in the basement instead of ductwork and a furnace. That’s not an accident. These houses were built before forced-air heat was standard, and running ductwork through a stone farmhouse or a narrow rowhome is often impractical or impossible without major renovation. So the original steam or hot-water system stayed, got repaired, got replaced in kind, and is still heating the house today.
One more thing worth knowing before you start: not every boiler in this county burns gas. Gas service isn’t universal across Delaware County, and plenty of older homes here stone farmhouses especially still run on oil. Most of what follows applies to both, but where the two differ, we’ve said so.
Steam vs. Hot-Water Boilers: A 60-Second ID Guide
Before you troubleshoot anything, figure out which type you have. The fixes and warning signs are different for each.
Steam Boiler
Steam boilers are common in the oldest Delco rowhomes. You’ll see a single pipe going into each radiator (sometimes two), a round sight glass on the boiler itself showing water level, and radiators that hiss or gurgle as steam fills them. There’s no pump circulating water, steam just rises through the pipes on its own. If you hear loud banging or clanking in the pipes, that’s a classic steam-system complaint.
Steam runs at surprisingly low pressure normal operating pressure on a residential steam boiler is roughly 0.2 to 0.5 psi, and half a psi is about the practical maximum. If your steam gauge is reading several psi, that is worth mentioning to whoever you call: it usually means someone has turned the pressure up to force steam past a distribution problem rather than fixing the problem.
Hot-Water (Hydronic) Boiler
Hot-water systems use a circulator pump to push heated water through pipes to baseboard units or radiators, then back to the boiler. You’ll see a pressure gauge (usually reading 12 to 15 psi when the system is cold) and an expansion tank nearby. If your radiators have two pipes going in and the boiler has a pressure gauge rather than a water-level sight glass, you’ve got hydronic heat.
6 Common Boiler Symptoms and What They Mean
- No heat or cold radiators: Could be a tripped breaker, a thermostat not calling for heat, a failed circulator pump (hot-water systems), or a stuck valve. On an oil system, a tripped primary control or a clogged nozzle or fuel filter are common causes. Start with the simple stuff before assuming the worst.
- Kettling or banging noise: In steam systems, banging pipes usually mean trapped condensate hitting steam, often from a pipe that’s lost its pitch or a failing steam trap. In hot-water systems, a kettling or rumbling sound from the boiler itself often points to mineral buildup or sediment on the heat exchanger, especially in older cast-iron units.
- Pilot light keeps going out, or the burner keeps locking out: A weak or dirty thermocouple, a draft issue, or a failing gas valve can all cause this. On an oil boiler there is no pilot light the equivalent symptom is the primary control locking out, often from a dirty nozzle, a failing photocell, or water in the tank. If it happens repeatedly, don’t keep relighting it and hoping, that’s a sign something needs attention.
- Pressure gauge dropping: On hydronic systems, slowly dropping pressure usually means a small leak somewhere in the system, or a failing expansion tank. Repeated pressure loss is not normal and shouldn’t be ignored.
- Short cycling: The boiler fires, runs briefly, then shuts off again and again. This can point to a bad aquastat, a clogged filter, or an oversized unit for the space. It wastes fuel and wears out components fast.
- Visible leaking: Water around the base of the boiler, on pipe fittings, or near the pressure relief valve means something is failing physically. This is one you don’t want to put off.
Safe DIY Checks Before You Call a Tech
Some of the simplest problems look identical to serious ones from the outside. Before you assume the worst, run through these checks:
- Check the thermostat is set to heat and actually calling for it, batteries included.
- Check the breaker for the boiler hasn’t tripped.
- Look for a reset button on the boiler or burner and press it once if it’s tripped. Once, and no more. On an oil burner in particular, every reset press pumps more unburned oil into the combustion chamber repeated attempts can flood it and turn a service call into a much bigger problem.
- Check the pressure gauge on hot-water systems against the table above. If it reads well below 12 psi cold, or anywhere near 30 psi, note that for whoever you call.
- Look at the water level in a steam boiler’s sight glass. If it’s low, that alone can shut the unit down safely as a protective measure.
If none of these get the heat back on, you’re probably looking at something mechanical that needs a professional eye. Our no-heat troubleshooting guide covers a lot of the same thermostat and power checks in more detail if you want a deeper walkthrough before calling anyone.
Stop and Call Immediately: Gas Smell or CO Warning Signs
None of the troubleshooting above applies if you smell gas, smell oil, hear a hissing sound near the gas line, or notice symptoms like headaches, dizziness, or nausea that improve when you leave the house. Those are signs of a gas leak or carbon monoxide issue, and they override every other step on this page. Get out of the house, call your gas utility or 911 from outside, and don’t go back in until it’s been cleared.
This applies to oil systems too. Oil-fired boilers produce carbon monoxide just as gas ones do, and a cracked heat exchanger or a blocked flue is just as dangerous regardless of what the burner is burning. Older boilers with aging flues and venting are more prone to these issues than newer sealed-combustion systems, which is exactly why annual inspection matters for a house with original equipment.
Repair or Replace? Signs Your Boiler Is on Its Way Out
Boilers, especially the cast-iron units common in Delco’s older homes, can run for decades with proper maintenance. But age alone isn’t the only factor. A unit that’s needed multiple repairs in the past year, is showing rust or leaking at the heat exchanger itself (not just a fitting), or is becoming harder to find parts for is telling you something.
If a repair estimate starts approaching a significant chunk of what a new high-efficiency unit would cost, that’s usually the point to seriously weigh replacement, especially since newer systems can cut your fuel use noticeably compared to a 30 or 40-year-old boiler. If you’re weighing that decision, it’s also worth checking our HVAC rebates and tax credits guide to see what might offset the cost of an upgrade.
Typical Delaware County Boiler Repair Costs by Fault Type
Repair costs on a boiler vary a lot depending on what’s actually broken, and no two Delco basements are quite the same. As a general rule, the simpler the part, the simpler the fix. A failed low-water cutoff or a thermocouple replacement tends to sit on the lower end of the cost spectrum since they’re straightforward swaps with widely available parts. A circulator pump replacement on a hot-water system runs a notch higher, since it involves draining and refilling part of the system and verifying proper flow afterward. Control board or aquastat failures tend to land on the higher end, since diagnosing them correctly takes more time and the parts themselves cost more. And if the issue turns out to be a cracked heat exchanger or a leaking boiler body, you’re generally looking at replacement territory rather than repair, since that’s not something you patch.
None of this is a substitute for an actual diagnosis. The honest answer is that the fastest way to know what your specific repair will cost is to have someone look at the unit, because symptoms can overlap between a cheap fix and an expensive one. That’s true of every boiler page you’ll find for this county, and it’s true of ours too, but at least now you know what questions to ask when someone gives you a number.
Why Delco Homeowners Trust Frontline HVAC
We work on the kind of houses this guide is written for, pre-1950s twins, rowhomes, and stone homes across Delaware County with steam and hot-water systems that most techs today barely see anymore. We’d rather walk you through what’s actually happening with your system than just quote you a number and a truck roll. If you’ve gone through the checks above and you’re still staring at cold radiators, reach out through our contact page and we’ll get someone out to take a real look. You can also browse our full heating services or learn more about our team before you call.
Frequently Asked Questions
Why is my boiler running but the radiators are cold?
On a hot-water system this usually points at circulation rather than heat: a failed circulator pump, a closed or stuck zone valve, or air trapped in the lines. Air is the most common and the easiest to deal with bleeding the radiators often brings a cold zone straight back. On a steam system, cold radiators while the boiler runs usually mean steam isn’t reaching them: a stuck air vent, a failing steam trap, or a pipe that has lost its pitch so condensate is blocking the run.
What pressure should my boiler be at?
It depends which type you have, and the two scales are nothing alike. A hot-water system should read about 12 psi cold and around 20 psi once it’s running, and anything approaching 30 psi is a problem that’s where the relief valve opens. A residential steam boiler runs far lower, roughly 0.2 to 0.5 psi. If a steam gauge is reading several psi, someone has likely turned it up to push steam past a fault rather than fixing the fault.
Is it safe to keep pressing the reset button?
Press it once. If the boiler locks out again, stop. This matters most on oil burners: each reset attempt sends more unburned oil into the combustion chamber, and repeated presses can flood it turning a routine service call into a far more expensive cleanup. A boiler that trips its reset more than once is telling you something is wrong that pressing a button won’t fix.
How long does a boiler last?
Cast-iron boilers of the kind common in older Delco homes routinely run 30 years and often more with regular maintenance considerably longer than a furnace. Modern high-efficiency units typically last 15 to 20. What usually ends a boiler’s life isn’t the boiler itself but the heat exchanger cracking or the body leaking, neither of which is repairable. Parts availability matters too: once a line is discontinued, a cheap fault can become an expensive one.