Currently all downpipes on our house are plumbed to a single drainage trench in our backyard, I'd like to collect solely from our garage roof (independent structure to house) and utilise a wet system design to store in 2x 4000L tanks, from there it would be connected to a pump which supplies a single tap for hose connection, and a manifold and sprinkler system for automated garden watering.
I'm a DIY enthusiast and plan to do most of the work myself, with sign off/final inspection from certified tradespeople. I plan to hire a trench digger for running all piping so I should get a pretty consistent grade along the drop for all pipes.
My garage roof is 9x5m=45m2 collection area, and I plan on installing a new downpipe for the system (and closing off the previous downpipe) on the south-west corner of the building. The eave height above ground level at this point is 3m and I understand I should install my leaf and mosquito screening at this point. I would then trench down to tank-1 in the southern corner of my yard (taking care not to interfere with the waste line running parallel).
The underground run from down pipe to tank 1 is approximately 14m, and I have measured fall as 1" over 2' - meaning a total fall of around 13cm over the length of the run. I plan to install a sediment trap per viewtopic.php?p=1193459#p1193459 - https://forum.homeone.com.au/viewtopic.php?f=35&t=92701&p=1844675#pImg977558 as well as low restriction inlet to tank 1.
These are the tanks that I'm planning to use - https://www.bushmantanks.com.au/product/4000-litre-domed-squat-rainwater-tank/ - this is dictated by the largest size that I can get through the garage for installation.
I'm currently planning to take overflow from the 2nd tank and dig a new drainage trench in my yard - run it to an agi-pipe with sock buried in the ground surrounded by gravel and geomesh fabric. My pump would also be connected to tank2 approx 150mm from the bottom of the tank, and use a floating pickup tube on the inside to take water from around 200mm below the surface layer.
- System purpose: vegetable irrigation only, non-potable use however will likely provide drinking water fill up for chickens
- 2x 4000L tanks -- should I connect in series, or parallel? - https://www.bushmantanks.com.au/product/4000-litre-domed-squat-rainwater-tank/ - https://www.bushmantanks.com.au/wp-content/uploads/2019/06/TXD910-Tank-Drawing-NSW.pdf
- Tank Inlet height 1300mm (bottom of strainer); tank height 1457mm
- Catchment area of 45m2 - postcode 2800
- Single downpipe (can add an extra one if it helps) with gutter sole height of 3000mm
- Wet line run of approx 14000mm with drop 1":2' -- I assume 100mm DWV pipe?
- DIY sediment trap and DIY waterbouy
- Low restriction inlet to water tank
Please let me know your thoughts on my system and help me with some further indication of what calculations I need to make, and sizing for my piping.
Yard diagram showing existing house waste collect (lines with measurements close to house) and sewer line (red line along the western boundary) is shown below. Coloured sections are my planned irrigation zones (my veggie patches). Diagram is north oriented.
Thank you so much for taking the time to read my thread.