Legionnaires risk

[MK22]

Hi all, a bit of a strange one and getting conflicting advice here, so any thoughts please share.
Where our kitchen used to be is now our living room, but we have a water stop tap coming from the concrete floor which used to feed the kitchen. Ideally we want rid of this stop tap, but we can’t locate where it branches from the main cold water feed to cap it there. I’ve been told you can’t cap it as there will be a risk of legionnaires, so we have to run something from it ie outside tap through the external wall. Others saying don’t worry about legionnaires , risk is minimal, it’s an underground cold water mains feed the temperature should never get warm enough to grow bacteria. So what do we do?! Box it in the best we can and make it look pretty with an outside tap we run once in a while, or cap it and don’t worry about bacteria? Different plumbers saying different things…

 

[CountryFan]

Ideally it should be removed altogether, if this isn’t practicable then no greater than twice the diameter of the pipe, so on a main could be 20mm mdpe so 40mm is the maximum, but if you’re digging it up anyway to cap then best to be removed, to prevent bacteria growth. What you can’t do, is leave the tap in without it being used which is called a dead leg.

 

[Wayners]

There are lots of houses with dead leg pipes that never get a problem but it's poor practice.
Any good plumber would advise all dead leg pipes should be removed.
A cold water pipe will be around 12 degrees centergrade in winter but could rise in summer. A dead leg with water in sat for years will become a problem with bacteria.

As for putting an outside tap on, that's a good idea although still not great because it can be unused.