Sizing the Infiltrator Below-Ground Tank
Infiltrator tanks do not require gravel backfill or other soil amendment, provided that the soil is no more than 70% clay. Interconnect the tanks with 1" - 2" flexible PVC.
This means that you will need a manhole for each tank. If you have 3-5 tanks and don't want so many manholes, then choose a single, larger, Purain HD for direct burial.
ConveyancePipe from the downspouts to the tank location with SDR 35 pipe. If you have multiple filters, you'll need a header at the tank to distribute the water.
PumpingA submersible pump with a floating filter intake will send the water to your irrigation system. A pressure-activated pump will start whenever the irrigation heads open, and also if you have a hose connection. They will also start and run continuously if you have a leak in your irrigation system. We can also synchronize the pump start with the irrigation controller. We can put a timer switch next to a hose connection. We like the second method a little better, but either can be best.
The pump will need a floating filter intake, as shown in the photo, to maximize water quality.
Standby ConnectionTwo common methods are a pressure regulating valve (PRV) or a solenoid valve. Either is acceptable in residential systems. Solenoid valve systems cost a little less conserve city water pressure better; PRV's are more readily available, last longer, and easier to service.
Standby Connection ProtectionMost municipalities are currently requiring an RPZ backflow preventer or air gap at a standby connection, unfortunately. We have new evidence that the rainwater does not contain any known contaminants, and would love to discuss this with your plumbing inspector. We would recommend a dual check valve, if that is typically an acceptable level of protection for a residential irrigation system. Dual check valves can be buried, which makes them easier to install. RPZ backflow preventers must be installed inside, or in an above-ground insulated and heated enclosure. Air gaps require re-pumping and therefore waste energy.
Georgia Water Tanks provides design assistance and on-site installation supervision for all packages.