Five Things You Need to Know About Secondary Hot Water Systems

In this blog, we’ll break down five key things you should know about these systems and pumps, and how to get the best performance and peace of mind.

1. Optimisation is key

As an installer, you play a critical role in influencing customer purchasing decisions and sharing best practice. That’s why you might want to start (if you’re not already) advising homeowners and building owners about why effective hot water pumps are critical to a hot water recirculating system’s performance and safety. To do this well, you must understand the role of optimisation and why it’s important.

Secondary hot water pumps need to be optimised for a range of reasons. Firstly, to ensure they are as energy efficient as possible and are providing your customers with the best value for money and energy savings.

Optimisation also makes sure the system provides a consistent temperature and means occupants within the home or building get instant hot water at the tap, helping to save water. By maintaining a constant flow of water between 50°C and 60°C, water is not stagnating within pipework, and therefore bacteria, such as Legionella, cannot grow - providing customers with added peace of mind.

It’s key to highlight that the hot water pump is like the ‘beating heart’ of a secondary hot water return system. If it is not set correctly or is old and in need of replacement, then it could be causing a strain on other equipment, such as the boiler, making it work harder. This in turn leads to poor energy efficiency and a shortened lifespan, both for the boiler and the pump itself.

The solution here is to fit new, adjustable speed pumps, such as Wilo’s Yonos PICO-Z range. The pump’s speed (flow rate) and pressure (head) can be changed to suit the needs of the building and means that it works only as hard as it needs to.

This also allows for better energy efficiency, as the Yonos PICO-Z can operate from as little as four watts of power to a maximum of 40. This results in less energy wasted, and the running of secondary hot water systems can be reduced by up to 70% when compared to outdated bronze pumps.

2. The end of the bronze age

Put plainly, bronze fixed speed pumps are antiquated. The systems are ancient in terms of their technology since they only offer up to three fixed speed settings which can draw as much as 100 watts, making them energy intensive.

Compared to modern adjustable speed pumps which offer a range of flow rate settings and pressure controls, it’s easy to see why manufacturers, such as Wilo, are saying goodbye to bronze pumps for good. That’s right, despite its popularity. From August 2025, Wilo’s SB30 will be discontinued, as we make a stand for better energy efficiency and sustainability.

3. Say yes to stainless steel

Stainless steel pumps are quickly becoming the more popular choice among the plumbing and heating industry. Pumps like the Yonos PICO-Z offer better energy efficiency and flexibility giving users complete control over how they want the pump to perform. There are 42 incremental adjustments for flow rate, and the same for pressure, meaning the pump can be set up more precisely to meet the demands of the system it is being used in.

Three pre-programmed speeds also allow for easy set-up and commissioning – making your life easier.

Stainless steel pumps are commonly found in commercial applications such as hospitals, schools, food manufacturing and industrial HVAC systems. However, thanks to growth in product ranges, they now cater for domestic hot water applications and are available in the small sizes required for homes. This means they can be used as a retrofit pump in residential properties, or in new-build homes giving you more flexibility over the projects you can work on.

4. How to change an existing hot water pump

If you’re facing a secondary hot water pump job and an existing pump that needs swapping out, then here are seven simple steps to follow to change it over to a Wilo Yonos PICO-Z pump:

1. Turn power off and check there is no power going to the pump

2. Isolate the pump at the gate valves

3. Remove the old pump

4. Install the new pump (make sure to use the new washers supplied with the pump)

5. Lag the pump with the thermal insulation shell supplied

6. Re-connect the electric connection to the new pump using the Wilo-Connector

7. Commission the pump (choose flow rate and pressure that will meet the demands of the building)

For a more detailed step-by-step guide, take a look at our other blog here.

5. How to vent and de-block the pump

You might encounter airlocks in a hot water system which reduce its efficiency if not cleared. Thankfully, you don’t have to worry about this with Wilo’s Yonos PICO-Z. Its automatic and manually triggered venting and deblocking functions make it much easier to maintain and keep hot water systems performing at their most efficient.

Ultimately, the latest secondary hot water pumps do most of the heavy lifting for you. Whether its adjusting settings or beating bacteria without you knowing, you can pass on peace of mind by simply making the switch from antiquated bronze pumps to more modern stainless steel counterparts and sharing best practice and tips with your customers and other installers.

Discover more about the Yonos PICO-Z range.