The correct design and installation of water systems help to control the potential for Legionella growth, however, older systems and systems where alterations have been made can increase this potential by having storage tanks that do not comply with current standards, incorrect fittings and the presence of dead legs, blind ends and inadequate back flow prevention.
The findings of a Legionella Risk Assessment may recommend the need to carry out certain remedial works to ensure your water system is up to current standards. BS8580-1:2019 says "During the inspection the assessor is looking for any elements of the design, construction or operation which could lead to conditions under which Legionella would be expected to multiply."