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When operating an HVAC system, maintaining adequate water levels is vital for a system’s efficiency and performance. Also important for efficiency and performance – as well as regulation compliance – is the prevention of backflow from a system’s contaminated fluids into the mains water supply. 

RPZ valves are legally mandated devices that connect to the mains shutoff valve, ensuring that water entering the downstream system is at a lesser pressure than the incoming supply. RPZ valves achieve this by using check valves to monitor the system, and relief valves to maintain pressure.  

Automatic Refill units help to maintain a continuous supply of water to minimize the risk of air ingress into the system, which is a very helpful byproduct of their water level maintenance as air can negatively impact the efficiency of heat transfer and circulation within the system. They also use a physical air gap that guarantees the prevention of backflow. 

Automatic Refill Units:

Also referred to as pressurisation packages, automatic refill units help maintain the correct water pressure and water level in a system by automatically compensating for water losses that can occur due to leaks, evaporation, and air bleeding in a system. They are calibrated to keep an HVAC system within its optimal water pressure range 

RPZ Valves:

RPZ (Reduced Pressure Zone) valves are backflow prevention devices that block a building’s closed loop system from sending contaminated water into the public supply. Including one in your setup is imperative when dealing with a system that has potential to create cross-contamination between the HVAC system’s water supply and the mains water supply. 

Benefits and Challenges: Refill Units

Benefits 

Automatic Operation:

Some refill units operate automatically based on the water volume within the HVAC system. Whenever the water level drops below a set threshold, the refill unit opens, allowing water into the system until the set level is reached. This automation ensures that the system consistently holds the water volume necessary for optimal performance.

Pressure Regulation:

Some refill units are equipped with pressure regulation features. This allows refill units to not only add water to the system, but also regulate the pressure to remain within the recommended range. This is crucial in preventing low pressure, which can affect the efficiency of the system and often leads to damage in the system’s components. 

Water Treatment:

Refill units may include water treatment features, such as the dispersion of inhibitors to prevent corrosion and scale formation within the HVAC system. Maintaining water quality is beneficial to the longevity and proper functioning of all system components.

Challenges

Valve Leakage 

Faulty valves and worn out seals can cause refill units to malfunction, leading to a continuous flow of water into the system. This can cause overfilling, and an increase (rather than maintenance) of system pressure. The best strategy to avoid valve leakage is a combination of using the correct valves for your system, selecting high-quality valves prior to installation, and regular maintenance that involves checking the valves, seals and connections for wear and tear. 

Incorrect Installation 

Improper valve placement, inadequate priming, or incorrect connection to the water supply can cause refill units to fail, resulting in suffering performance, costly inefficiencies and unnecessary delays. 

Benefits and Challenges: RPZ Valves

Benefits 

Backflow Prevention:

Backflow occurs when the flow of water in a plumbing or HVAC system reverses direction, potentially allowing contaminated water to enter the clean water supply. RPZ valves are designed to prevent backflow by creating a barrier that stops water from flowing back into the public water system, saving developers from the hefty costs of repairing a back flowing system and dealing with the associated fines, frustrated stakeholders and time-intensive processes involved in remedying a back flowing system.  

Reduced Pressure Zone Design:

The RPZ valve includes two independently acting, spring-loaded check valves separated by a ‘reduced pressure zone’. In normal operation, the check valves are closed, preventing backflow. If a pressure drop occurs in the public water supply, the pressure in the reduced pressure zone is lower than the supply pressure, opening the check valves and discharging water into the atmosphere, creating a zone of reduced pressure. This helps ensure that any contaminants are pushed away from the public water supply, no matter whether pressure is normal, increased, or decreased. 

Challenges

Compliance with Local Regulations and Codes:

The installation and maintenance of RPZ valves are often governed by local plumbing codes and regulations. Many municipalities require the use of RPZ valves in specific situations to protect the public water supply, so the use of RPZ valves is often a headache-saving decision that ticks compliance boxes, giving you peace of mind. 

Regular Testing and Maintenance:

RPZ valves require more regular testing and maintenance to ensure their proper function when compared to refill units. Periodic testing, typically performed by certified professionals, involves checking the valves for proper closure and verifying that the reduced pressure zone is maintained. If an RPZ valve fails a test, it may need repair or replacement to maintain effective backflow prevention. If your RPZ valve requires testing or maintenance, contact Masterflow today

Moving Forward 

Refill units and RPZ valves are both essential components in HVAC systems, serving slightly different aspects of system functionality—refill units for maintaining water levels and preventing pressure drops, and RPZ valves for backflow prevention, protecting the public water supply.

In the event that an RPZ valve fails, the air gap provided by a refill unit will ensure the continued safety of the system avoiding any leaks into the water mains. 

Whilst there is little product variation between RPZ valves on the market, there are various features which are included in some refill units, and excluded from others. If you’re unsure about which refill units are best for your individual product needs, send Masterflow an enquiry about your refill unit options and one of our experts will be in touch shortly