Radiators in Torrevieja and the Costa Blanca

The radiator hot at the bottom and cold at the top

It’s the most common radiator complaint we get in Torrevieja, Orihuela Costa and around. The lower section is hot but the top is lukewarm or even cold. The cause is almost always the same: air trapped inside the radiator. Air gets into the circuit for several reasons (pressure top-ups, microscopic valve leaks, incorrect maintenance) and, being less dense than water, settles at the highest points of the system, typically the radiator’s upper part. That air stops hot water flowing across the whole surface and dramatically cuts radiator output, which means rooms heat slowly and the gas bill goes up because the boiler works harder to compensate.

The fix is bleeding, an operation anyone can do with the radiator bleed valve, but it needs to be done in the right order. Start with the lowest radiator in the house and work up floor by floor. Switch the boiler off and let the circuit cool. Open the bleed valve slowly, wait for all the air to come out and steady water to flow, then close. Repeat on each radiator. At the end, check circuit pressure and top up if it’s dropped below 1 bar.

When the problem is more serious

If after bleeding the radiator still heats poorly, more serious causes are possible. Sludge build-up is the first. Over years, heating-circuit water generates oxides and mineral residues that settle in radiators, especially in the lower section. That sludge reduces the useful flow cross-section and creates cold zones. The fix is full chemical flushing of the circuit with a specific descaling product introduced with the boiler off, circulated for a few hours, then fully drained before refilling with new water dosed with corrosion inhibitor.

The second common cause is a stuck or failed thermostatic valve. Modern TRVs have an internal pin that can seize after months of disuse (which happens every Costa Blanca summer when heating isn’t used). To prevent it, cycle the TRV heads max and min every couple of months in the off-season. If the valve is stuck, remove the head and free the pin with a very gentle tap, or replace the whole valve.

Replacing old radiators

Cast-iron radiators in older homes still work but have lower thermal efficiency than modern steel or aluminium. Their thermal mass makes them slow to heat and cool, penalising temperature-by-temperature regulation. For a home with intermittent central heating use, swapping to modern aluminium can significantly improve thermal response.

Low-water-content aluminium radiators are the most efficient for most modern installations. Heat fast, cool fast, allow fine hourly programming without comfort penalty. Steel panel tubular is a common alternative with good price-to-quality ratio. For bathrooms we recommend towel rail radiators combining room heating with towel drying.

Individual TRVs per radiator

A very profitable upgrade is fitting thermostatic heads on each radiator. Each room has its own independent temperature control, allowing different setpoints by use (warmer living room when occupied, cooler unused guest room) and saving energy without losing comfort. Install is simple when radiators already have conventional valves: just swap the manual head for a thermostatic one.

For apartments with central communal boilers, combining TRVs with individual consumption meters lets each home pay for the heating actually used, much fairer than proportional split by surface area when there are no meters. It’s a mandatory upgrade in many communities under European regulation.