Hello, Large low risk office, 68,000 square feet. 500 employees, water tank fed and mains hot and cold water to toilets etc. Typical stuff, nothing out of the ordinary. We have a company who have carried out a legionella RA for us, control measures include, monthly outlet temp testing, flushing of single shower, annual clean of water tank and calorifiers etc. However there is no testing or sampling done of the water to determine levels of legionella bacteria. I would have thought there should be some periodic sampling done to ensure the controls in place are working etc? looked at L8 and it only seems concerned with high risk suff such as colling towers and spas etc.. So question should a large office need sampling done and if so how often? Im think six monthly as a reasonably timescale...

I suggest you've answered your own question. Low risk premises - no sampling required. I would hope your specialist contractor would confirm that. See also para 68 of the 2013 L8. Sampling isn't the norm.

Pretty simple justification for not sampling actually - check the guidance document HSG274 Part 2 - Paragraph 2.119 onwards. This covers sampling (or the lack of need to) in domestic hot and cold water systems. In essence it states, no need to do it unless you can have some reason to start doing it. The default position is 'no to sampling' as opposed to higher risk systems such as cooling towers where the default position is very much 'yes to sampling'.