Wilo TOP-Z 1 phase hot water bare pump bronze

Hot water pumps, also called hot water circulators, keep domestic hot water moving round a loop of pipework from the cylinder or water heater to the taps and back. This means hot water reaches outlets quickly instead of running cold first, and it helps keep the whole loop up to temperature. They are used on hot water systems in homes and in commercial buildings.

Materials and model codes

Pumps for domestic hot water have stainless steel or bronze housings, rather than the cast iron used for many heating circulators, so do not swap one type for the other. Some manufacturers use a model code that gives the port size in millimetres and the maximum head, with letters for the housing material and connection, for example N for stainless steel and F for flanged. Larger pumps have flanged connections, while smaller ones have threaded ports; check whether unions or flanges are included or need ordering separately. The pumps in this range run on a single-phase supply.

Choosing and controlling a pump

To replace a pump, match the port size, connection type, length and duty of the old one. A time switch can limit running to the hours when hot water is normally used, to cut energy use, and some pumps detect a thermal disinfection cycle. To control legionella, hot water should be stored at 60°C or more and reach at least 50°C at outlets within a minute of running, so the circulation loop must keep water hot. Pumps on drinking water must be suitable under the Water Supply (Water Fittings) Regulations 1999, and electrical connection should be made by a competent person.

For heating pumps and cylinders, see circulation pumps and cylinders and water heaters.