As is per usual for many of the past failed RWH regulations, it is probably traceable to a bureaucrat who's ego overrode the need to seek the appropriate expert advice.
I'm…

The wallopers will just say it's a civil matter.
@ did you get a receipt or was it an agreed "cashie", i.e. no GST?

The damp proof course sits at the bottom of the weep hole.
The location of a damp-proof course or flashing serving as a damp-proof course, must be not less than—
(i) 150…

You just need the gutter and downpipe sizes to be compliant with the NCC for the roof area harvested and have the downpipes connected to a LPOD.
You need to…

Can you hear it from outside the house?

Any thoughts about utilising the roof area? Do the height limits allow it?

Do you envisage any issues with the neighbour's tree in consideration of it being a multi storey development?

It doesn't hurt to ask.

Of interest, how high is the retaining wall?

The bottom of the downpipe has been taped (see the black tape) to seal the necessary gap between the downpipe and the adaptor that would normally prevent the downpipe from…

https://www.vba.vic.gov.au/__data/asset ... rector.pdf

The rainhead's overflow lip at the front has to be a minimum 25mm below the gutter's discharge sole. Hard to tell from the photo if it complies but it looks…

It's a classic example of aesthetics subjugating function where style usurps precedence over practicality.

This is a very challenging situation, made much harder by not being on site.

Firstly, I think that I originally overestimated the % coverage of the additional roof areas to…

Once you know the basics, the rest is easy. Read my post in the thread linked below.
viewtopic.php?p=1919271#p1919271

Unfortunately, you are correct.
Paradoxically, a lot of emergency overflow solutions discharge to atmosphere whereas the Gutter Pumper diverts water.
WA gutters are sometimes fitted with small side spouts colloquially…

It is important to note that while the National Construction Code (NCC) provides minimum guidelines and standards, it does not explicitly mandate following manufacturers’ guides/instructions as this provision was deleted…

A 20 year old Adelaide woman died today after the gum tree she was resting under dropped a branch.
https://www.9news.com.au/national/adela ... 2712fe3d19

I'll comment further on the above.
The contractor is either an idiot or an unethical opportunist!
Water doesn't fall down a downpipe, it flows down the walls but an adaptor's flow transition…

Thank you for the added information and for adding the downpipes to the photo.
I'll give a summary before I give course of action recommendations.
Roof drainage regulations
Victoria has a variation…

I need the answer to a few questions before I can give some advice.
I take it that the only gutters that overflow are those servicing the patio roof.
I notice vegetation…

You don't have a warranty?
What country are you in?

The downpipe just around the cormer is weird as it is connected to another downpipe by plumbing that downpipe across the wall and around the corner. The downpipe around the…

You have changed the numbers on a couple of the pipes.
Just dig at the base of the 3 pipes near the corner to see where they connect.
I also see that…

Pipe 1 is a vertical riser.
A vertical riser rises from a subsurface pipe that is supplied by one or more remote downpipes.
You have a downpipe just around the…

Waiting.....
Information asked for is required before a full answer can be given. There are also other design issues that the owner is most probably not aware…

Thanks for the photos.
Your first two photos show a 'dry' system pipe that discharges into the meshed basket at the top of the tank. This downpipe should not be overflowing.…

Just when you think you have heard of everything.....
Unfortunately, plumbers have no formal training in rainwater harvesting and numerous bad installation practices are endemic.
I…