PHAM NEWS | MARCH 2026 20 Heat Pumps
Why anti-freeze valves should never be optional
a system is damaged during a cold snap, the first question asked is whether adequate frost protection was in place. A correctly specified anti-freeze valve provides a clear and defensible answer.
Protecting installations Heat pump technology is under intense scrutiny as the UK transitions toward low-carbon heating. Every failure, leak, or damaged system risks reinforcing scepticism among homeowners and undermining confidence in the technology as a whole. For installers, the stakes are
high. Delivering reliable systems that perform not just in ideal conditions, but in worst-case scenarios, is key to building trust and securing repeat business. Anti-freeze valves may not
be the most visible component of a heat pump system, but their impact is significant. In a market where reliability and professionalism matter more than ever, they represent a small addition that delivers substantial peace of mind.
With colder winters, increasingly volatile weather patterns and a growing reliance on electrically driven heating systems, installers are facing a new reality as frost damage poses a growing risk to heat pump systems. Ed Morris from Altecnic explains.
around system efficiency is gradually being joined by the more urgent topic of system protection. With colder winters, increasingly volatile weather patterns, and a growing reliance on electrically driven heating systems, installers are facing a new reality as frost damage is now a real and growing risk. At the centre of this issue is the
A
anti-freeze valve. Once considered an optional extra, particularly in milder regions, high-temperature anti-freeze valves are fast becoming a non-negotiable component of best-practice heat pump system design.
Hidden vulnerability Unlike traditional boilers, air source heat pumps are inherently exposed to outdoor conditions. The hydraulic circuit between the outdoor unit and the heating system is vulnerable whenever water temperatures fall and circulation stops. This can happen more easily than many homeowners realise, such as during power cuts, control faults, standby periods, or extended shutdowns. When temperatures drop
below freezing and water remains static in the system, the consequences can be severe.
s air source heat pump installations continue to accelerate across the UK, the conversation
Frozen pipework can split, heat exchangers can crack, and entire outdoor units may be rendered unusable. The resulting repair costs are significant, often running into thousands of pounds, and are rarely covered by manufacturer warranties if frost protection has been inadequately designed. For installers, this doesn’t just
mean an unhappy customer, but also could lead to reputational damage, call-backs and potential liability.
Ed Morris Technical manager at Altecnic
Anti-freeze valves operate
independently of electricity, controls, or system logic. They respond purely to temperature, making them
reliable even during complete power failure.
Beyond software Many modern heat pumps include software-based frost protection, typically activating circulation pumps or electric heaters when low temperatures are detected. While these systems are effective under normal operating conditions, they rely on the critical assumption that there will be a continuous power supply. In the event of a power
outage, a scenario most likely during extreme winter weather, software protection is instantly disabled. With no circulation and no active heating, water in exposed pipework can freeze rapidly. This is where mechanical
protection becomes essential. High-temperature anti-
freeze valves provide a simple, passive safeguard against freezing. Installed in the
outdoor hydraulic circuit, these valves open automatically when the water temperature drops to a critical threshold, typically around 3°C. By safely discharging water from the system, they prevent internal freezing and the destructive expansion that follows. Crucially, anti-freeze valves
operate independently of electricity, controls or system logic. They respond purely to temperature, making them reliable even during complete power failure. For installers, this adds a layer
of protection that cannot be achieved through software or other components alone.
Best practice changes As heat pump installation scales up, expectations around installation quality are rising. Specifiers, manufacturers, and insurers are increasingly aligned on the need for robust frost protection strategies, particularly for systems installed in exposed locations or regions prone to sub-zero temperatures. Including anti-freeze valves
as standard is quickly becoming part of professional best practice rather than an upsell. It demonstrates foresight, technical competence, and a commitment to long-term system reliability. Importantly, it also protects installers from disputes. When
p The iStop Anti-Freeze Valve provides reliable mechanical frost protection for heat pump systems
pump systems. These valves open at around 3°C to discharge water, closing again once temperatures rise to about 4°C, all without needing electrical power or control signals. They provide mechanical frost protection precisely when software-based strategies are unavailable or powerless at low temperatures. We offer several configurations
in this range suitable for different system requirements, such as the iStop PLUS compact for space-restricted installs, and the iStop Anti-Freeze Valve with swivel connection. ◼
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The iStop A strong example of this hardware-based protection strategy is Altecnic’s Series 108 iStop Anti-Freeze Valve range, designed specifically for heat
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