Boronia et al – It’s actually worse than that.
In order to keep muddy water out of the stormwater system, the all so practical EPA (NSW) has in the past advised Councils to require the wash water from residential carwash bays to be directed to the sewerage system via a coalescing plate oil/water separator set below-ground.
All that does of course is to load-up the sewerage system with even more stormwater during rain events (that dump rainwater on the carwash bay), so the Sewerage Authorities then required carwash bays to be bunded and covered by a roof with a 20° overhang, and for that separator to be totally emptied every 3 months.
For what purpose I ask? When society has resolved all of its real pollution problems, maybe then it can focus on the muddy water generated by people washing their cars; as if Owners Corporations don’t have enough maintenance responsibilities already!
My advice, don’t have a carwash bay and either wash cars on the grass, or spend $10 on the high-pressure washer at the local servo.
Gees….. I feel better now!