How does a hot water recirculating system work?

We are well aware that water is a precious resource and designers, installers, and all professionals in the AECO sector play an important role in reducing water waste and therefore in safeguarding this resource.

During the design phase, many choices are made aimed at water saving. Among these, there is certainly the possibility of equipping the system with a hot water recirculating system.

Let’s discover together this simple yet ingenious method to reduce waste and increase comfort, while also recommending the use of a specific hydraulic systems design software that will help you make the right decisions for the project and the environment.

What is a hot water recirculating system?

To begin with, it is important to specify that for domestic hot water, indicated simply by the acronym DHW, we mean the water intended for domestic use within a home or building, from kitchen use to personal hygiene. DHW, which can be heated through various systems, allows daily operations to be carried out safely and without the risk of coming into contact with viruses or bacteria.

Optimizing the supply of domestic hot water is an important goal in terms of bills and environmental impact. This is where a hot water recirculating system comes into play.

The hot water recirculating system (DHW) is a mechanism, a circulator more specifically, that is connected to an additional line parallel to the hot water line.

Equipping the plumbing system of a home or building with a recirculating system allows you to:

• ensure immediate availability of hot water at various points of use, even if the point is far from the boiler or heat source;
• minimize heat losses along the pipes;
• reduce water and energy waste;
• increase user comfort.

Due to the purpose for which a DHW recirculating system is designed, this system, although clearly optional, is particularly recommended for long pipe runs.

How does a DHW recirculating system work?

The mechanism behind these systems is ingenious yet simple: it involves constantly circulating hot water through the pipes so that it is readily available near showers and faucets.

The steps of this recirculation process are:

1. heating the water with a heat source;
2. sending the water to the dispensing points through the pipes;
3. unused hot water in the pipes is sent back to the heating system through a return circuit.

It is estimated that, especially on long pipe runs, the arrival of hot water at the most distant dispensing points from the heat source can take over a minute. Equipping the system with a return circuit helps reduce these waiting times to around a maximum of 15 seconds.

How are recirculating networks classified and what are the types of recirculating systems?

Recirculating networks are classified based on the connection point with the domestic hot water supply pipe. This distinction allows us to identify three types of DHW recirculating networks:

1. user or collector recirculation: this type of recirculation is the most branched and expensive as it reaches directly the user withdrawal points. It ensures a high level of comfort and is therefore mainly used in hotel and healthcare facilities, but it presents the disadvantage of imbalance in the flow, especially on long networks;
2. floor recirculation: this second type of recirculation reaches the distribution manifolds of the accommodations, allowing a good level of comfort with lower costs. It is the solution most commonly used in residential buildings with predominantly horizontal distributions;
3. column recirculation: this third type, finally, reaches the supply pipes at the top of the risers. As easy to understand, it is the simplest of the three types in terms of implementation and allows the correct balancing of water flows thanks to the insertion of specific devices.

Types of hot water recirculating system

What are the advantages of a hot water recirculating system?

We know well that water is a necessary and precious resource, and the last thing we would want is to use it unreasonably without worrying about limiting waste.

Among the practices aimed at reducing water waste, we find the hot water recirculating system which, as we have anticipated, allows us to reuse hot water already heated and not waste it, while increasing the comfort of users who see a significant decrease in the waiting times for water at the desired temperature.

So, we could summarize the advantages of a hot water recirculating system in:

• economic advantage: thanks to the reduction of water and energy waste;
• environmental advantage: as we ensure a reduction in resource consumption and greenhouse gas emissions.

Of course, we must not forget the purpose of this system, which represents an advantage in itself, namely the practically immediate availability of hot water at all dispensing points, leading to greater user comfort.

Environmental sustainability and energy efficiency make the hot water recirculating system an interesting system to propose and implement.

Let’s remember that sustainability and energy efficiency can be achieved through the correct sizing of the systems.