Rainwater treatment starts before water enters your cistern. Use a pre-tank filter to reduce incoming debris, manage sediment inside the tank, and then filter pumped water in this order: sediment, tannin removal when needed, carbon, and finally UV disinfection. These six methods work together, with the exact equipment chosen for your water quality and intended use.
Roof runoff can carry leaves, twigs, shingle grit, and other debris. Keeping that material out of storage is the first step toward a cleaner, easier-to-maintain rainwater system.
Six Rainwater Filtration and Treatment Methods
1. Pre-Tank Filtering
Filter roof runoff before it reaches your cistern to reduce the debris entering storage. WISY is one option, but it is not the only prefilter we offer:
- WISY Vortex roofwasher filter, up to 2,200 square feet and the larger 5,500-square-foot model.
- Single Outlet Monjolin Filter.
- Maelstrom Rainwater Filter with Shark Cage or Plastic Cage.
The right choice depends on your roof area, pipe layout, and tank installation. Browse our roof washers and prefilters or ask us to help match a filter to your system.
2. In-Tank Sediment Management
A calming inlet directs incoming water toward the bottom of the cistern without unnecessarily stirring up settled debris. A floating intake filter draws water below the surface rather than from the sediment layer at the bottom.
These components help manage debris in storage, but they do not replace the filtration and disinfection stages after the pump.
3. Sediment Filtration
After water leaves the cistern, sediment filtration comes first. A sediment filter captures suspended particles before water reaches the remaining treatment equipment.
Select the cartridge rating and flow capacity to suit your system and the requirements of the equipment downstream. Replace cartridges as needed rather than waiting for severely reduced flow.
4. Tannin Removal for Discoloration
Tannins from decomposing plant matter, such as leaves, can give rainwater a yellow, brown, or tea-colored appearance. A tannin removal filter addresses this discoloration.
When tannin treatment is needed, place it after the sediment filter and before carbon filtration. It is a targeted stage for discoloration, not a substitute for sediment filtration or UV disinfection.
5. Carbon Filtration
A carbon block filter follows sediment and any tannin-removal stage. Carbon can help improve taste and odor; specific contaminant reduction depends on the cartridge's specifications.
Choose a cartridge suited to your water and flow rate, and maintain it according to the manufacturer's instructions.
6. UV Disinfection
UV disinfection comes last, after sediment, tannin treatment when needed, and carbon. UV treats microorganisms rather than physically filtering out particles or removing discoloration.
The UV unit must be sized for your flow rate, supplied with water that meets its manufacturer's requirements, and maintained as directed. Clear-looking water alone does not establish that it is safe to drink; drinking-water systems need appropriate treatment design and water testing.
Putting the Stages Together
Start with pre-tank filtering and good in-tank sediment management. After the pump, the sequence is sediment → tannin removal when needed → carbon → UV. Each stage has a different job, and not every system needs a tannin filter.
Need help selecting prefilters or building a treatment system for your cistern? Call or text Rain Brothers at 937-949-1100. We can help you choose equipment for your layout, water quality, and intended use.
