http://www.tankworks.com.au/Create-a-Tank.aspx
http://www.tankworks.com.au/Our-Product ... Tanks.aspx (click on the second photo)
1. First flush is fitted at the top of the vertical riser!!! Wet systems remain full of water to the level either at the top of the riser or the first flush pipe fitted to the riser as in these examples. When plumbed as per the photos, the first flush pipe will fill with the water in the riser while the first flush is still in the downpipe at the other end of the wet system.
2. Unless there is very heavy rain, the velocity of water up the wet system's vertical riser will not flush debris from the underground vertical pipe and wet systems are renown for accumulating sediment and stagnating. There has been no provision made for a low restriction flow path.
What I was trying to explain was that in Victoria, if recycled water is connected to the estate, it must be connected to the toilets, even when a tank is optioned. However, having recycled water connected negates the Victorian requirement to option either the mandatory solar HWS or the rainwater tank.
I don't know your BASIX requirements but I was suggesting that if BASIX also had a similar mandate to connect recycled water to the toilet, then perhaps they also have the provision that having a tank was no longer necessary. It would however seem not to be the case but I would still check with BASIX.
If there is no provision, then it is unfortunate as the BASIX requirement for a rainwater tank is all about water conservation and the recycled water would satisfy that criteria if connected to sanitary flushing. Opting out of having a tank would save people a lot of money and they could always get one much more cheaply later on if they wanted. The Victorian experience however is that not all builders are savvy to such regulations and it never hurts to make your own inquiries.
There are things that you can make sure are done correctly such as ensuring that a submersible pump is properly installed. I also see a lot of pressure pumps that have failed because the suction pipe was connected directly to the pump with a 90 degree elbow, causing cavitation. A bit hard for the untrained eye to pick up.
Good luck with everything.