What is the recommended pipe run length when installing sanitary hot water plumbing pipe?

The UK Water Regulations say that hot water must reach the outlet within 30 seconds, and at a temperature of 50°C or above. The maximum length recommended is 12 metres for 15mm pipe. Therefore care needs to be taken when planning the location of the hot water source and manifolds. When the distances involved are greater, consider installing a ring circuit as a secondary circulating system, with a bronze circulating pump. This should be at least 28mm. Pass this through manifolds, with multiple tee-offs . Locate the manifolds within 12 metres of the outlets it will supply.