Combi Boiler Problems

white radiator image by Ekaterina Sidorenko from

Combi boiler systems provide a heating source in many household and small industry environments, particularly in the United Kingdom and other European countries. Replacement costs for combi boilers are expensive, so the identification and resolution of common problems can be vital components of cost-effective use.


Hard water can cause scaling on the heat exchanger, and this can prevent the combi boiler from operating efficiently. In turn, any water circulated through the system will leave mineral deposits inside pipework and radiators. The cost of replacement components can be quite high, but plate-to-plate heat exchangers will usually help to alleviate the problem.


Many home and businesses owners assume that combi boilers provide instant hot water, but this is not the case. Combi boilers actually fire up once there is a demand for water, and it can often take up to a minute for hot water to reach taps. As well as being inconvenient, latency is one of the few areas where water wastage occurs in combi boiler installations.

System Pressure

During periods of low demand, combi boiler systems hold pressure fairly well. However, periods of high demand can often lead to drops in pressure throughout the system, particularly during summer months when neighbours are using hoses or sprinkler systems in their gardens. This can be particularly frustrating, and it is often difficult to get warm water in daytime hours during these periods.