Bronze pumps are commonly used as hot water circulation pumps in secondary hot water systems. Many traditional bronze models use fixed-speed operation, which means they run at a constant speed and offer limited adjustment options.

Stainless steel pumps are used for the same type of application, but newer models are often designed with additional control functions. Depending on the model, these can include selectable flow or pressure settings, which may allow the pump to be adjusted more closely to the requirements of the system.

In addition, stainless steel is widely used in applications involving potable water because of its corrosion resistance and suitability for such environments.

Both bronze and stainless steel pumps can be used in domestic and commercial secondary hot water return applications.

Bronze pumps are often found in existing or older residential hot water systems. For example, the Wilo SB30 has been used in a range of residential applications to circulate secondary hot water through a system.

Stainless steel pumps are also used in domestic and commercial settings, including applications such as hospitals, schools, food manufacturing facilities and HVAC systems, subject to the requirements of the installation. Many stainless steel pump ranges are now also available in sizes suitable for residential properties, including retrofit and new-build applications.

The main limitations depend on the specific model. Many older bronze pumps use fixed-speed motor technology and offer limited adjustment options. In practice, this can mean the pump runs continuously at one of a small number of preset speeds, regardless of changes in system demand.

Some older models may also have higher power consumption than newer electronically controlled pumps. In addition, fixed-speed pumps are generally less flexible to commission because they do not offer the same range of control settings as pumps with adjustable operating modes.

This does not mean that bronze as a material is unsuitable. The suitability of any pump depends on the application, the system requirements and the product specification.

From August 2025, Wilo will discontinue the sale of its SB30 Bronze Pump and instead focus on alternative hot water pump solutions within its portfolio.

Stainless steel is commonly selected for potable water applications because of its corrosion resistance and suitability for use in such environments. Installers should always ensure that the selected product is compliant with applicable local regulations and product requirements, including Regulation 4 of the UK Water Supply (Water Fittings) Regulations 1999 where relevant.

From an operating perspective, newer stainless steel pump models may include electronically controlled motors and selectable settings that allow operation to be aligned more closely with system requirements. Depending on the pump model, installation and commissioning, this can help reduce unnecessary electricity consumption compared with fixed-speed alternatives.

Any assessment of product durability, service life or material-related benefits should be considered in the context of the specific application, water quality, operating conditions and maintenance regime.

Fixed-speed pumps operate at their selected set point continuously and do not automatically adapt to changing demand within the system. In some applications, this can result in higher electricity consumption than necessary.

By contrast, pumps with selectable controls can be configured more precisely for the system they serve. Depending on the model and settings chosen, this can allow the pump to operate at a lower output where full performance is not required at all times.

For example, the Wilo Yonos PICO-Z range offers multiple selectable flow settings and a constant pressure setting. This enables installers to match pump operation more closely to the needs of the system.

Depending on the application, commissioning and comparison baseline, electricity consumption may be reduced compared with older fixed-speed pump models. Any percentage saving claim should always be understood in the context of the specific comparison conditions.

Ease of installation and maintenance depends on the pump design and the installation conditions. In many cases, newer hot water pumps are designed with features intended to simplify handling, electrical connection and servicing.

Compared with some older pump designs, newer models may be lighter, more compact or easier to orient during installation. Some models may also include features such as tool-free electrical connection, venting functions or service-support features to assist installers.

For example, the Wilo Yonos PICO-Z range includes features such as the Wilo Connector, rotatable pump head and functions for venting and de-blocking. Certain models are also supplied with insulation accessories. These features can help simplify installation and maintenance, depending on the specific application.

If error indication features are included, these may also support faster diagnostics during servicing.

Programming and commissioning methods vary by manufacturer and model, so installers should always follow the product instructions supplied with the pump.

For the Wilo Yonos PICO-Z, settings are adjusted using the control interface on the pump. Depending on the application, installers can select from a range of flow settings or use the constant pressure function to align pump operation with system requirements.

The correct setting will depend on the system design, required flow and pressure conditions, and the installer’s commissioning assessment.