Our model DC15F257 Pipe Interrupter was specifically designed to be installed on the outlet of a laboratory tap that has the removable nozzle taken off, providing the highest level of protection against back siphonage, as required under the Water Regulations. This model now has an integral clutch mechanism, which locks the device in place once fully screwed on. This makes it much more secure and prevents any chance of it from being removed after installation — ensuring the Fluid Category 5 protection is always in place.
Why Laboratory Taps Require Fluid Category 5 Protection
Laboratory environments present some of the most serious contamination risks in any building. Sinks and water outlets in labs can come into contact with biological agents, chemical compounds, and other substances that represent a severe danger to human health. Under the Water Supply (Water Fittings) Regulations 1999, these outlets are classified as Fluid Category 5 — the highest risk category — and require the highest level of backflow protection.
Back siphonage can occur when mains pressure drops unexpectedly, creating a negative pressure that draws fluid back up through the outlet and into the supply pipework. In a laboratory setting, this could result in hazardous contamination of the wider water system — a scenario the Regulations are specifically designed to prevent.
How the DC15F257 Works
The DC15F257 DC Pipe Interrupter fits directly onto the outlet of a laboratory tap once the removable nozzle has been removed, using a standard half-inch BSP thread. It operates as an atmospheric vacuum breaker: if back siphonage conditions arise, the device opens to atmosphere, breaking any siphon before contaminated fluid can travel back into the supply.
The integral clutch mechanism introduced in the current version is a significant improvement for compliance assurance. Once the device is screwed fully onto the tap outlet, the clutch engages and prevents removal without a deliberate override — meaning the protection cannot be inadvertently or deliberately defeated during normal use.
WRAS Approval and Regulatory Compliance
The DC15F257 is approved for use under the Water Regulations and meets the requirements for Fluid Category 5 back siphonage protection in open outlet applications. Arrow Valves recommends that all laboratory tap installations are reviewed by a competent person to confirm the correct device is specified for the specific risk present.
For a full overview of Arrow Valves DC Pipe Interrupter models — including variants for urinals and outside taps — contact our technical team.
