I have needed to upgrade my (currently dry) rainwater harvesting system to a wet one. My household is using more water than we collect. I'm pretty sure I have ample roof catchment but not enough downspouts. Like everyone else, I've gone pretty deep on rainwater research and basically from the forum god saveH2O I've learnt that even our local plumbers have no idea what's going on (and this can be seen from all my neighbours' archaic designs in their newly built homes).
I have hit a bit of a brick wall in understanding how to calculate the required number of downspouts (DPs) and the subsurface pipe sizes in order to achieve adequate flushing velocity, along with the diameters of the pipes along the run and into the tank.
I've tried to illustrate very clearly my current existing infracstructure, along with the placement of two new gal (with internal poly) 22.5k tanks. My initial idea is that I would link them so I am drawing from both.
I also would like a bit of a quick sketch diagram on setting up the modern style rainwater tank design with a diverter into the base to achieve a dynamic head according to the current water level. I'm planning on drawing water from the top of the tank via a floating filter but first I need to figure out the pipework.
Helpful information:
- 2x 22.5k tanks at same level
- 90mm tank overflow capacity
- Flat roof on tank (40 mm from peak to sides to allow for rain runoff)
- Gutters are about 125h x 125w with weep holes halfway on the sides
- Roof pitch 20-25 deg* (guestimate)
- Head from bottom of lowest house gutter to tank base about 4m (around 1.6m to top of tank)
- 259mm 1:20 ARI (4.31mm/min)
- Existing design is using 90mm downspouts which drain dry to existing tank (to be changed to wet pipes).
- Rain from the gutters on the far side of the house (DPs 5 & 6 and any new ones) need to be piped via the new wet pipes to the opposite side of the concrete driveway (shown in grey).
- I haven't shown where the current placement of pipes are as I am creating a wet system and redoing/upgrading the pipework so I figured it would be confusing.
Main Question:
- How to calculate my roofs LPM and M/S in order to know how many DPs I need for the upgrade, each at what diameter and then what diameter subsurface pipe do I need to get me to the tanks. Also, what I need when I go back into the tanks, along with the pipe/s sizes I need for the overflow.
I can illustrate a quick idea of how I want to pump into/from and link up my tanks but for now this is the part that I feel really stuck on. Would appreciate any help, especially from saveH2O!
Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅
Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Link to higher resolution of images here: https://www.dropbox.com/s/up2l87i65szcr ... 1.pdf?dl=0