I'm currently building a 75000 L potable rain harvesting system in rural Oregon. Due to many building mistakes (that's a whole other nightmare) I've had to move my (4) 18927 L tanks farther down hill from my house. This has now raised many questions I wasn't originally figuring into the design.
I've been reading the posts here for the last few months as I try and deal with the many questions I have and was hoping some of the experts here could help me with a few of the remaining questions.
Below is my current design setup: (i've tried to keep it metric but excuse me for any mistakes)
- 167 sq.m house with 185 sq.m roof
- 1:20 ARI for this area is about 177 mm in 24 hour period
- (4) 18927 L x 3.65 m high tanks on an 203 mm thick concrete slab
- The tanks and slabs are roughly 122 meters from the house downhill with drop of about 6 - 8
meters. The top of the 3.65 m tank is roughly 2 - 3 meters below the bottom of the gutters.
- This is going to be a dry system. I've glued and buried 76 mm pvc running from each of the 6
downpipes,three on each side of the house.The left and right side of the house converge into a
76 mm DWV Y pipe and then a single 76 mm pipe feeds into a 1.2 m x 305 mm inground diverter
then into the top 76 mm inlet of the 4th tank.
- 4 of the downpipes will have leaf filters connected right below the downspouts
- All 4 tanks are to be connected to each other with the following scenario: Tank 4 fills first
and overflows via a 76 mm connection at the top to tank 3. There will be a water quieter
attached to the bottom of the pipe in tank 3. Tank 3, 2, 1 will be connected by the bottom
inlets via a 50 mm pvc pipe. Tank 1 will be the tank connected to the pump and pressure tank,
it will also have a 100 mm overflow pipe.
- Regardless if I use flexible or rigid pvc at the bottom of the tanks, each tank will have it's
own discharge pipe that will be operated by independent ball valves and will discharge over
the hill in front of the tanks. My thought here is that in the event I need to empty a tank
due to contaminants etc. I want to be able to still access and fill the other tanks. (See
1. I know it's best to have flexible connections at the base of tanks, but I'm having a heck of
a time trying to find potable, flexible, weather resistant tubing. What do you guys use? If I
were to use 50 mm rigid PVC for the connections they would be on the cement slab, so I
believe the only thing that would break or upset them would be a jolt from the cascadia fault
Oregon is next to.
2. Since the top of my inlet tank is about 2 - 3 meters below my gutters I've figured I should
have enough head pressure to fill the tank?
3. Will the 50 mm pipe connecting tanks 3,2,1 be large enough to accommodate the 76mm inflow
from tank 4?
4. I was planning on having my 450 L pressure tank, pump and pressure switch in the pump house
right next to the tanks. Would it be better to have the pressure tank and pressure switch in
the house which is 122 m up the hill or should I leave the pressure switch next to the pump
and put just the pressure tank in the house?
I'm attaching a hand drawn schematic of my proposed setup. Hopefully it works.
https://www.dropbox.com/s/9u7ivvajqtdw3 ... p.JPG?dl=0