If I was to print that rubbish out off the internet and submit it to the council for approvals they would laugh at me.
A plumber wouldn't quote on that sketch, nor should you accept an PS estimate based on that.
I'm laughing at it. Absolute amateurs!
Norts33...when you reply to a quote, can you please write your reply outside the box at the bottom?
Their 'sealed system' is a charged wet system. No big deal.
Re those diagrams, is there mosquito proof gutter guard? Lol.
If the diverters shown on the infeed pipes are first flush diverters, they are in the wrong positions! For example, the next time it rains, the one at the top of the vertical riser will only fill with the settled water that was retained in the riser after it last rained while the 'new' first flush will still be in each downpipe!
If you have recycled water connected, you do not need a water tank connected to the toilets and laundry to comply with the Victorian 6 Star standard.
You need to ask the builder whether the tank is a detention tank and if so, what is the council's Permissable Site Discharge (PSD). It is very strange that the council didn't know anything about it when you spoke to them when the builder has told you that it is a council requirement.
If there is a PSD because of the flood overlay which seems not only reasonable but the only logical explanation, then I am surprised that the tank's required capacity is only 2,000 L. Something isn't right here. What is your roof area?
Re the +$3,000 for a 2,000 L tank, check out the link below that has a 2,000 L tank for $625. The business has branches that service your area.
https://www.asctanks.com.au/product/urb ... ater-tank/
Maybe there is a hidden hydraulic assessment floating around somewhere but I can't possibly see a hydraulic assessment for a detention system with a limited PSD only having a 2,000 L tank.