Central heating systems, radiators and controls in Croydon

That is sludge, not air. Magnetite is iron oxide worn off the inside of steel radiators and pipework, and it is heavier than water, so it settles along the bottom of the radiator while the hot water flows over the top of it. Bleeding will do nothing, because there is no air in there to let out. The fix is cleaning the system, either chemically over a few weeks or with a power flush, then fitting a magnetic filter and dosing inhibitor so it stops building up again.

That one is air, and bleeding it usually sorts it out. The better question is where the air keeps coming from if you find yourself doing it every few weeks. Repeated air means a leak drawing air in, an expansion vessel that has lost its charge, an open-vented system pulling air down the vent pipe, or corrosion generating hydrogen inside the radiators. We would rather find the cause than leave you bleeding radiators every month for the next ten years.

Our full central heating systems start at £3,400, which covers the boiler, radiators, pipework, controls, a system clean and a filter in a straightforward house. What moves the figure is the number and size of radiators, whether the pipework can be reused or has to be renewed, how far the boiler is moving from where it sits now, and whether the gas supply pipe from the meter is large enough. We give you a fixed written price after the survey, not a range.

If the radiators heat evenly, the pipework is sound and the layout suits how you live, a boiler replacement from £1,950 is usually the sensible choice and we will say so. A full system earns its cost when the pipework is old microbore that has silted repeatedly, when radiators were sized for a house that has since been insulated, when you are adding rooms, or when you want zoning the existing wiring cannot deliver. Part of the survey is telling you honestly which of those you are in.

Water takes the easy route, so left alone the radiators nearest the boiler take most of the flow and the far ones get whatever is left over. Balancing means throttling the near radiators at their lockshield valves until every radiator drops roughly the same temperature between flow and return, usually around 11°C. It takes a couple of hours with a clamp thermometer and costs nothing in parts. It is the cheapest heating improvement most Croydon houses have never had done.

Only if the system needs one. A power flush is the right answer where there is genuine sludge: radiators cold across the bottom, black water when you bleed, a pump or motorised valve clogging up. It is not a sensible routine annual purchase, and on old microbore pipework it needs a careful hand, because forcing debris through 8mm pipe can block it rather than clear it. We look at the system water first and will tell you if a chemical clean over a few weeks would do the same job for less.

Yes, and we wire it in properly rather than leaving batteries and double-sided tape to do structural work. Most Croydon houses running a seventies or eighties system have no thermostat cable to the hall, so a wireless stat with a receiver at the boiler is normally the answer. If you want room by room control we can pair smart TRVs to it, though it is worth knowing that per-room control works far better on a system that has been balanced first.

Usually not. The pin under the TRV head seizes in the open or closed position after a summer of never moving, and freeing it with a little penetrating oil and some patience fixes it more often than not. If the pin is corroded away or the valve body is weeping, the valve gets replaced, which on a sealed system means draining that part of the circuit down. We would rather replace a failing valve than hand back one that will seize again next autumn.

Every radiator except the one in the room where the room thermostat lives, usually the hall or the living room. If that radiator has a working TRV too, the two controls fight each other: the TRV closes the radiator, the room cools, the thermostat calls for heat, and the boiler runs against a system with nowhere to send it. That radiator should sit on plain valves and be set once. It is a five minute correction and we find it on a lot of systems.

A full system in a typical three bedroom Croydon semi takes two to four days, depending on whether floors have to come up and how much pipework is being renewed. A boiler-only replacement in the same position is usually a single day. You will be without heating and hot water for the working part of that, and we plan the drain-down and refill so nobody is left cold overnight. You get the actual dates before we start.

It is worth chasing, yes. A healthy sealed system holds its pressure for months, so a gauge that falls every week means either a leak somewhere in the pipework or radiator valves, or an expansion vessel that has lost its charge. Beyond any water damage a hidden leak can do, every top-up carries fresh oxygen and fresh hard water into a circuit that was never meant to see either, and that is what eventually becomes sludge. Leak tracing is quoted on the job once we have seen it.

We work across Croydon and the CR postcodes from our base on Highbury Avenue in Thornton Heath, so Norbury, Selhurst, South Norwood, Addiscombe, Shirley, Purley, Sanderstead, Selsdon, Coulsdon, Kenley and New Addington are all routine for us. Normal hours are Monday to Saturday, 7am to 8pm, and we keep emergency cover running 24/7 for no heat in cold weather. Call 07534 841885 and tell us what the radiators are doing.