Yes. Rainwater collected from a clean surface and stored covered works well for Kratky. It’s naturally low in minerals, so your nutrients make up most of what’s in the solution. You still need to add a complete hydroponic nutrient.
Why Rainwater Works
Tap and well water can contain a lot of dissolved minerals, which add to what the nutrients supply and affect pH. Rainwater starts with very little, which makes mixing a predictable solution easier.
Collecting It Cleanly
- Collect from a roof and gutters that are clean. Some roofing materials and treatments can add contaminants.
- Let the first rain after a dry spell wash the roof before you collect, or use a first-flush diverter.
- Strain out leaves and grit.
Storing It
Keep stored water covered and dark. That stops algae and keeps mosquitoes from breeding in it.
Check the pH
Rainwater can be slightly acidic. Mix your nutrients first, then test the pH of the finished solution with drops or strips and adjust if needed.
Related guide: growing Kratky off-grid.
