Douche / shattaf & water regs

[WWilts]

Jeremy Harris wrote:

"It's a hand-held, trigger operated shower head, with a tightly concentrated spray, often referred to as a shattaf."

(our plumber here calls it an arse washer - AW)

Will a double check valve suffice to bring an AW within the water regs? Unvented system.
Our plumber says Building Control can impose £15k fine if an AW is fitted in an unvented system. Risk of contamination.