When your radiators aren’t getting hot all over, it can be a frustrating and chilly experience! Winter has truly hit the homes of Milton Keynes and there’s nothing worse than expecting a warm glow that doesn’t ever come. Here are some common causes, things you can check, and how Lime Heating can help restore consistent heating.
Common causes of cold or poorly heating radiators
1. Trapped air
Air gets into the heating system during top-ups or servicing. Because water is denser than air, the air rises to the top of the radiator, stopping hot water from filling it properly. This results in cold spots at the top while the bottom stays warm.
2. Sludge, rust or debris build-up
Over time, metallic debris, rust and sludge can build up inside the radiator or pipework. That sludge settles in flow paths and blocks hot water from circulating, especially towards the bottom or middle of the the radiator, causing cold patches that don’t warm up, despite bleeding your rads.
3. Stuck or faulty radiator valves
If thermostatic radiator valves (TRVs) or lockshield valves are seized or not adjusted properly, they block or restrict the flow of hot water into the the radiator. Even brand-new radiators can suffer if valves are incorrect or improperly installed.
4. Unbalanced heating system
In some systems, one radiator might heat up faster or hotter than others. Radiators further from the boiler or on different floors may get less hot water flow. Balancing the system ensures each radiator gets its fair share of hot water. Pro tip: our Lime Care packages including radiator balancing and bleeding
5. Boiler or pump issues
If the boiler isn’t producing enough hot water or the pump is weak, flow might be insufficient. This means radiators further away might struggle to get hot water.
DIY checks you can try
Here are some things homeowners can check before calling in a professional:
- Bleed your radiators: turn off heating, let radiators cool, then open the bleed valve at the top corner until water flows, releasing trapped air. Check out our handy video on how to do it here.
- Check radiator valves: ensure both inlet (TRV) and lockshield valves are open. If a TRV is stiff, remove the head and check the pin for movement.
- Look out for cold patches: feel for cold spots at the top, middle, or bottom — they give clues about the issue (air, sludge, or flow restriction).
When you should call a professional
Some issues are best left to qualified heating engineers, especially when:
- Sludge or rust is blocking multiple radiators — a full power flush might be needed.
- Valves are seized or need replacing / rebalancing across the whole system.
- Boiler or pumps need diagnosing or replacement.
- You want to install a magnetic filter or inhibitor to prevent future build-up.
How Lime Heating solves the problem
At Lime Heating, we help homes in Milton Keynes get their radiators working as they should:
- We perform professional power flushes to remove sludge and debris from your entire heating system.
- We rebalance the system so each radiator gets even heat, reducing cold spots and energy waste.
- We install magnetic filters and inhibitors to protect your system long-term.
- Our Gas Safe engineers ensure your boiler and rad system is safe, efficient, and ready for cold weather.
Don’t let cold radiators cost you comfort or money. Book a radiator health check or power flush with Lime Heating to restore efficient warmth to every room.
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