Receive help from one of our partners
Find an installer nearby
Why is the radiator cold at the bottom? And how to fix it.
If your radiator is hot at the top but cold at the bottom, the fix is often simple. Whether one or several, we’ll help get the warmth flowing again.
What's causing the issue?
Causes and solutions when the radiator is hot at top, cold at bottom.
In most cases of uneven heating radiators it's a matter of either trapped air, build-up of sludge (a mix of rust, dirt, and debris that settles over time), which blocks the flow of hot water or even a faulty pump.
The solutions: Flushing out the sludge or powerflushing your system can restore full heat, this needs to be done by a professional. If trapped air is the issue, bleeding your radiator could be all it takes. This can be done by you. If you’re unsure, it’s always best to contact a professional.
How you can release trapped air by bleeding your radiator
1/4
- 1/4
Turn off your heating and let the radiator cool completely.
- 2/4
Bleed the radiator to remove trapped air. Learn how with our simple radiator bleeding guide.
- 3/4
Check, if the valves are open and operating correctly.
- 4/4
Feel the radiator after bleeding. If the bottom is still cold, sludge is likely the issue. You can book a radiator flushing with an installer partner. Find your nearest here.
After bleeding the radiator
What to do if bleeding the radiator didn't solve it.
If you have done all the necessary steps like bleeding your radiator to solve the issue yourself and they still heat unevenly, it's time for a professional. Let one of our installer partners flush the system for you.
Two ways to get instant help from Vaillant professionals.
Room unevenly heated
Just one radiator cold? Here’s how to fix it.
If only one radiator is colder at the bottom, the issue is likely isolated to that unit. Bleeding it is a good first step, but if that doesn’t solve it, the radiator may need cleaning inside.
Check if the valves are fully open too. A stuck or partially closed valve can restrict water flow, leading to uneven heating. If the problem persists after bleeding and valve checks, it could be time to remove the radiator and flush it manually (let an installer do it).
Stay warm year-round
Prevent cold spots in the future with these simple tips.
- Bleed your radiators regularlyAim to bleed your radiators at least once a year (ideally before winter) to keep them heating evenly from top to bottom.
- Book a professional system flush every few yearsA professional powerflush clears debris out, improving circulation and restoring heat to every part of the radiator
- Check your boiler pressure regularlyIf the pressure drops too low, your system might not heat properly. Keep an eye on the pressure gauge and top up when needed.
- Have your boiler serviced annuallyAn annual service ensures your boiler and system are running efficiently, safely, and with optimal pressure.
