I have replaced an outside tap which did not have a NRV. There is a service valve under the sink which has an arrow. Is this a NRV? Original was fitted 1989 by builder during extension work.
The arrow on the SV merely indicates direction it should be fitted, it doesn't have an NRV.
You van buy outside taps with inbuilt double check valves that comply with regs.
1. The regulations only allow ones with a built in check valve to be used to replace an outside tap that already had one.
2. A non-return valve has a hexagonal bolt head on the outside, usually in the centre of the body.
3. The service valve is not likely to incorporate a non-return valve. If it does, it will have a hexagon on it per 2. above.