IBC totes are a popular way to store rainwater for gardens and irrigation. Sizing a system comes down to two numbers: how much water your roof can collect, and how much you want to store.
How much water a roof collects
A common rule of thumb: one inch of rain on 1,000 square feet of roof yields about 623 gallons, before losses. Real systems lose some water to splash, evaporation and first-flush diverters, so plan on less.
How many totes
- A 275 gallon tote holds about the runoff from one inch of rain on 440 sq ft of roof, before losses.
- A 330 gallon tote holds about the runoff from one inch of rain on 530 sq ft, before losses.
- Totes can be linked at the valves so they fill and drain together.
Setting them up
- Use totes whose previous contents were non-toxic, and clean them before use.
- Cover the bottles to block light and slow algae growth.
- Screen the inlet to keep out debris and mosquitoes.
- Set totes on a level base that can carry the full weight — about 8.34 lb per gallon of water.
- Fit an overflow that directs excess water away from foundations.
Check the rules
Rainwater collection rules differ by state, province and municipality. Check current local regulations before you build.