Does an outside tap need a check valve?

An outside tap needs backflow protection suited to the contamination risk created by its use. A double check valve is common, but Water Regs UK warns that protection depends on what the hose can contact, so it is not a universal answer for every garden or cleaning setup.

A hose submerged in a pond, bucket, chemical sprayer or other contaminated water creates a different risk from a hose used clear of contaminants. Do not leave a hose end submerged, and disconnect accessories when they are not in use.

Water Regs UK advises checking with the local water undertaker because backflow devices have operating limits and the appropriate arrangement depends on the application. A WaterSafe-approved plumber can assess the intended use, location and freezing protection.

The fitting itself must also be suitable and correctly installed. A product approval or compliance mark does not by itself prove that a particular installation meets every requirement; layout and use matter too.

Describe the intended use when asking for advice: watering plants, filling a pond, using a pressure washer and connecting a chemical applicator do not present identical risks. The hose route, any submerged outlet and the possibility of back pressure all matter. Protect the tap and pipe from freezing and isolate and drain it where the design provides for that. Never assume a small valve built into a hose connector upgrades the whole installation to the protection required by the water undertaker.

Keep the installer's certificate and product instructions for the property, particularly where the outlet serves equipment that may change later.

Sources

• What backflow protection is needed for hose taps? — Water Regs UK, accessed 14 November 2026.
• Compliant water fittings — Water Regs UK, accessed 14 November 2026.

On Leatmere

See outdoor tap kits, check valves and backflow and backflow.