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Radiator Heat Common Problems and Simple Fixes

Rather than forcing heated air through a system of ducts like a conventional furnace, you may have a steam or hot water radiator that warms your home through a series of pipes. Radiators were invented in the mid-1800s and many older homes still have them. 

Cost-effective and energy-efficient home radiators are starting to make a comeback in some areas. There are even portable electric radiators, such as the DeLonghi Dragon4Digital Programmable Portable Radiator Heater, that use a special diathermic oil to radiate heat into just one room.

Like any heating system, a radiator may need to be fixed. They can develop problems that range from simple to complex and must be maintained regularly. Here are some general maintenance tips, along with common problems and how to fix them.

General maintenance tips for radiator heat

Steam radiators typically require the most maintenance. Once a week, flush the low-water cutoff in the boiler. Once a month, with the system on and hot, check the safety valve to ensure that steam can freely escape (be careful, as the escaping steam will be extremely hot).

During your monthly check, open the valves on both sides of the water level gauge. Turn off the system, let it cool, and add water if the level is low—or invest in an automatic water valve that will slowly add water as needed. Take a frequent peek at the steam gauge. If it falls outside the normal range turn the system off and call a professional immediately.

Hot water radiator heat is not quite as complex to maintain, but it’s important to keep up with it. Other than occasionally lubricating the circulating pump motor with lightweight oil, the biggest maintenance issue is purging the system (unless your system has an automatic purge). To do this, open the valves until water comes out and then close them again. This removes any air from the system. Then drain the boiler according to the manufacturer’s instruction. Do this in the fall, shortly before heating season, and periodically throughout the season.

Also, keep an eye on the pressure gauge and, unless your system has an automatic pressure-regulating valve, release air as needed. Call a professional if you have any trouble getting the system to maintain the proper pressure.

Once a year, have an HVAC professional check both steam and hot water radiators. Turn the system on at least once during the heating season if it isn’t in regular use.

Electric oil-filled radiators don’t require regular maintenance. Keep an eye on them, though, as they can develop electrical problems like any other heater, or even spring a leak. Problems with these radiators typically require professional assistance.

Common radiator heat problems

All heating radiators, whether steam or electric, can develop some relatively common problems. Among these are:

No heat/radiator feels cold to the touch:

This is often due to an electrical problem or a clogged pump. Make sure you haven’t blown a fuse or tripped a circuit breaker and that the thermostat is operating normally. If the electricity is functional, clean the pump according to the manufacturer’s instructions, and release any excess air that may have gotten trapped inside. You can also flip the diverter valve beside the boiler off and back on. If none of that works, contact an HVAC professional. Replacing the pump can cost several hundred dollars depending on your geographic area and the specifics of your system.

Cold top, warm bottom:

If the radiator feels cold at the top but warm at the bottom, it may need to be “bled.” Turn off the pump, put a bucket down to catch water, and open the valve with a radiator key. When water starts flowing into the bucket, close the valve.

Warm top, cold bottom:

A radiator that is warm at the top but cold at the bottom can mean lots of things. Try removing the radiator from the wall and flushing it with water. If that doesn’t work, call a professional. It’s hard to predict these repair costs because it depends on what the problem is and how long it takes to diagnose and fix.


A radiator leak can be tricky to DIY when the source isn’t obvious. Unless you’re extremely handy, it’s generally best to call a professional. Repair prices vary dramatically based on how long it takes to diagnose and whether the problem part can be repaired or needs to be replaced.

Simple radiator fixes

For both steam and hot water radiators, there are some basic steps you can take to fix annoying issues and keep them working their best:

Check the slope.

Radiators work best when they are set at a slight slope toward the inlet pipe. If you need to create one, add a 1/4-inch wood piece under the vent. It can go a long way toward reducing knocking noises.

Replace blocked vents.

Over time, paint and corrosion can block radiator vents, trapping air inside. An easy fix for old radiators that aren’t heating properly is to swap out the vent for a new one. They’re usually attached by a couple of screws and most hardware or big box stores carry new ones. Just make sure you buy the proper size.

Open or close valves.

Radiator systems have numerous valves, which sometimes end up in a partially-open/partially-closed position. If you’re hearing odd noises or notice uneven heating, check all the valves. Make sure those that should be open are completely open and those that should be shut are completely closed.

Fix valve leaks.

While a radiator leak can be tough to trace and repair, valve leaks are relatively easy. Most of the time, a valve leak is actually coming from the large-cap nuts at the vertical or horizontal connections. Use two big wrenches to tighten these nuts. If necessary, remove the valve head and tighten the gland nut just underneath.

Improve aesthetics.

If you have a radiator that works well but is showing its age, consider investing in a radiator heat cover. Heat covers were originally used to moderate the heating output of oversized radiators. Modern thermostats take care of that problem, but heat covers are a great way to give aging radiators a makeover. Choose from simple wooden cabinets, ornate metal patterns, or even custom entertainment centers.

The bottom line

Radiators are an older, but energy-efficient option for home heating. Like any heater, they require regular maintenance and are prone to occasional issues. But with a little know-how, you can fix many common radiator problems yourself.

Frequently asked questions


How do you turn a radiator on and off?


It’s important to know how to turn on a radiator and how to turn off a radiator. You do both tasks with the valve at the bottom. Turn it clockwise to turn the radiator off; and counterclockwise to turn the radiator on.


Why would a radiator not heat up?


There could be an electrical issue or a clogged water pump. See above for how to check and fix these issues.


Why are my radiators cold when the heating is on?


If the top is cold, but the bottom is warm, you may need to bleed the valve. See above for information on how to do that. If the top is warm but the bottom is cold, you may need to call for a professional heating repair.


What to do if a radiator is not working?


If a single radiator is not working, it may contain trapped air. Use a radiator key to release the air.

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