cold water pipework lengths

[bossmillie]

Is there a maximum length that a cold water pipe can be run as a single length, where it can be used for drinking water? I'm sure I heard that over a certain length it had to be pumped and on a recirculation loop, to prevent bacterial build up during periods of inactivity.
If this is the case what are the applicable regulations or guidlines.

many thanks for your help

[happybaggy]

The regulations to which you refer apply to domestic hot water draw off pipework, not cold water.
Mains cold water for drinking purposes can be any length but if it is fixed too close to heating or domestic hot water pipework it should be insulated; not to keep heat in, but to keep heat out, so that when the pipe is not being used the water does not warm up to the point where bacterial growth is possible.
The only exception to the length of a cold water pipe is if it is an unused dead-leg which is capped off. In this case the dead-leg must be cut back and capped where the pipe branches off the main water flow, otherwise an air lock could form at the end of the pipe and as air expands more than water, the build-up in pressure could burst the pipe.
Hope this helps.

[bossmillie]

many thanks happybaggy for your prompt reply, that makes it very clear.