Why are my radiators cold at the top but hot at the bottom?

Fixing Radiators Cold at the Top

This is the most common radiator problem and is easy to fix yourself in most cases.

Why It Happens

Air naturally enters your heating system over time through:

• Topping up system pressure
• Small leaks in the system
• Hydrogen gas from corrosion (in older systems)
• Air dissolved in water being released when heated

How to Bleed Your Radiators

What You'll Need:

• Radiator key (from any hardware store, about £2)
• Old towel or cloth
• Small container to catch water

Step-by-Step:

1. Turn on heating - Let radiators warm up fully to push air to the top
2. Turn off heating - Wait 10 minutes for pressure to stabilise
3. Start upstairs - Air rises, so bleed top floor radiators first
4. Place cloth under valve - The bleed valve is at the top corner
5. Insert key and turn anti-clockwise - Just a quarter turn
6. Listen for hissing - This is air escaping
7. Close when water appears - Don't let much water out
8. Check boiler pressure - Top up via filling loop if below 1 bar

How Often to Bleed

• Once at the start of each heating season (October)
• Whenever you notice cold spots
• After any system repairs or pressure top-ups

When to Call a Professional

• You need to bleed radiators frequently (monthly or more)
• Water coming out is black or rusty
• Boiler pressure keeps dropping
• Multiple radiators have problems

For persistent radiator problems in Wolverhampton, Walsall, or Cannock, call NK Gas Services on 07404 922458.