I'm finalising the stormwater for our new house in Adelaide, and would like input on how it's going. This is the basic plan as designed by our builder and their engineers. The red is the charged system, and green the dry. It includes some yard drains for surface water.
So far, the downpipes are in, but I have yet to do the underground work. I've been following a bit of SaveH2O's advice from various forums, but the design I have in mind is a bit of a compromise. I don't see this being used for drinking water, so while I want to do it well, there's a limit to the expense and trouble I want to go to.
I'm looking at installing the Leaf Eater Ultra leaf diverters. It seems they can be mounted right under the gutter, and so preserves as much head as possible. The ground at the base of the tank is about 2.6m below eaves level, and the tanks I'm looking at have inlets at around 2200. Currently the downpipes are 75mm, but I'm thinking to change them to 90mm on the charged system, mainly because 75mm is such an odd size, and fittings are hard to come by. Then I'm thinking to go to 100mm before entering ground level.
The site is on reactive soil, so is there an advantage in using flexible couplings at any point?
I have in mind to add a silt trap as suggested. How do you normally mount the outlet of this? I can picture a poly pipe emerging from the ground - do you then tie it to a stake or something like that? Perhaps there's an advantage in running it into a yard pit so that it has a better chance of draining the wet system?
Then there's the low restriction inlet. I assume with this that you need a valve on the tank inlet, so you can close it off to open the sediment purge? One thing I wonder is if using the 100mm Tee section, the geometry could be awkward around the tank. The riser would be close to the tank, so the base of the tee is going to be headed away from the tank - can you than have sharp bends to bring it back into the base of the tank?
One thing I am wondering is with the low restriction inlet, is there still need for the riser? Is that for high rainfall events? but even then I'm thinking that the filled 40mm pipe may have about a s much capacity as the overflow anyhow?
What's the best way to get the extra drillings into the tank? Is that something you order the tank with, or drill them through later? Are some tanks easier than others to do this?