One heavy rain — hundreds of liters off the roof. The Amish don't waste well water on irrigation.
System
Gutter → downpipe → filter (mesh for leaves) → barrel. A 200-liter barrel is standard. A 50 m² roof with 25mm rain yields 1,250 liters. One barrel fills in one downpour.
Filtration
First rain after drought washes dirt off the roof. The Amish use a 'first flush' — diverting the first 20–30 liters past the barrel. A mesh screen stops leaves and insects.
Storage
Closed barrel — against mosquitoes and algae. Dark color blocks light (algae won't grow). A tap at the bottom for watering. Overflow pipe at top — so the barrel doesn't burst.
Use
Garden irrigation. Rainwater beats tap water — no chlorine, plants grow faster. Soft water — ideal for laundry. For drinking — only after filtration and boiling.