Emergency Boiler Repair in Sidcup (DA14)

More than a third of DA14 households live in purpose-built flats, 3,568 of them or 36.4% in the 2021 Census, the third highest share of the 18 districts. The buildings are mostly older than the boilers inside them. The Valuation Office’s 2026 count of homes by the decade they were built finds only about one home in eight built after 1999, and since April 2005 the Building Regulations have required a replacement gas or oil boiler to be a condensing one in all but exceptional cases. So in most DA14 homes with a condensing boiler, flats included, the boiler arrived long after the building did, and its drain had to be found in a layout never planned for one.

Where no drain could be reached, a pump went in.

Condensate pumps in boiler cupboards

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A condensing boiler produces water as it runs, and the water has to go somewhere. The industry’s guidance is for it to fall by gravity to a drain inside the home: an internal soil stack by preference, otherwise a kitchen, bathroom or shower waste. In a flat that is not always possible. The drain may be higher than the boiler, there may be a doorway between the boiler cupboard and the nearest waste, or the pipe would have to run a very long way, and in each of those cases the guidance says a condensate pump should be used. A pump like the Grundfos Conlift is a small separate unit with its own power lead. Grundfos designs it for no more than 60 starts an hour. The boiler’s water runs down into its tank, a float switch starts the pump when the level reaches one point and stops it when the level falls to another, and the water is pushed along a thin hose to the drain. The Conlift also has an overflow switch that can be connected to the boiler and set to stop it if the tank reaches its alarm level. Everything turns on that word can. If the switch is wired in, a pump that fails stops the boiler and the house goes cold. If it is not, the boiler carries on making water for a tank that cannot empty. There is a thermal switch as well, which stops the motor if it is overloaded and restarts it once it has cooled.

Not to be confused with a frozen condensate pipe outside.

Start with what you can see without opening anything. Is the boiler showing a fault, and is the pump making an alarm? Is the pump’s power on at its plug or switch? Grundfos’s fault table gives four reasons for a pump that will not run: no power, a blown fuse, a damaged cable, or the thermal switch having tripped. Only the first is yours to put right. The rest are inside the unit, and Grundfos says the power must be off before any work on it. Do not tip the tank or pour anything into it either: Grundfos describes boiler condensate as very aggressive.

We start with the pump, not the boiler. Power and its fuse, then the float, then the hose and the non-return valve, because Grundfos lists a squeezed or broken outlet hose and a non-return valve that will not open among the causes of a pump that runs without shifting water. The tank gets cleaned if it needs it, and we find out whether the overflow switch is wired to the boiler, so you know which kind of failure to expect next time. Then the boiler is reset the way its own instructions say. Whether that is the end of it depends on the pump: some come back with a clean, some need replacing, and you hear which before anything is ordered.

The pump failing is no reason to scrap the boiler, but if yours is due anyway, we also arrange boiler installations, and a replacement is when to ask whether a new one needs a pump at all.