Define "backflow prevention".

'Air gap'?

'High loop'?

'Check valve'?

If it does not define "backflow prevention" as one of those three, then anything which the HI considers to be helping restrict backflow could meet that, and, if it does define backflow prevention as just one of those and gives no alternative(s) - then a recognized alternative would need to be written up as a deficiency in need of repair ... and how stupid would that make the HI look?

HI: 'Dishwasher does not have an air gap - install an air gap.'

Plumber: 'Does not require an air gap, it has a high loop, which the manufacturer allows as does the code.'

HI: 'Dishwasher does not have an air gap - I am required to report that by TREC as a deficiency requiring repair.'

Plumber: 'Man, you guys sure have stupid laws, making you write something up for repair which meets code and manufacturer's installation instructions and does not need to be repaired.'

HI: 'I know, but I am still required to do so. Dishwasher does not have an air gap and needs to have an air gap installed.'

I feel for you guys.