Is It Legal to Collect Rainwater in Wisconsin? Uses and Permits

Yes, it is legal to collect rainwater in Wisconsin. No state statute or administrative rule prohibits capturing rain that falls on your property, and no state-level permit is required to put a barrel under a downspout. What the state does regulate, through its plumbing code, is what happens to that water after you collect it, especially if you want to pipe it into your house.¹

What You Can Use Collected Rainwater For

Outdoor, non-potable uses are the simplest. Watering gardens, irrigating lawns, washing cars, and rinsing outdoor equipment are all allowed without treatment or special equipment. This covers what most Wisconsin homeowners actually want to do with harvested rain, and it is essentially unregulated at the state level.

Indoor non-potable use is allowed but conditional. Wisconsin’s plumbing code permits stormwater reuse for uses like toilet and urinal flushing, provided the water meets the treatment standards in SPS 382.70.² Those thresholds include a pH between 6 and 9, suspended solids no greater than 5 milligrams per liter, and a free chlorine residual between 0.1 and 4.0 milligrams per liter. Meeting them requires a treatment system listed under NSF/ANSI 350 or NSF/ANSI 350-1, or one specifically approved by the Department of Safety and Professional Services.³

Rainwater Cannot Be Used for Drinking

Wisconsin’s plumbing code requires water used for drinking, cooking, and food preparation to come from a source approved under NR 811 (public water systems) or NR 812 (private wells).³ A private rainwater harvesting system doesn’t qualify under either. NR 812 covers drilled and driven wells with construction, testing, and Department of Natural Resources approval requirements that a rooftop collection system cannot meet. If your property has no access to a public water supply, a permitted private well is the approved alternative for potable water, not a cistern.

Connecting a System to Your Home’s Plumbing

The moment rainwater piping touches your home’s plumbing, the rules get stricter. Wisconsin’s code classifies a connection between a potable water supply and piping carrying water from a non-potable source as a high-hazard cross-connection.⁴ That triggers the strictest backflow prevention requirements in the code.

In practice, a dual-plumbed system where rainwater feeds toilets while municipal water feeds sinks and showers needs approved backflow prevention devices, and the two systems have to stay completely separate. Non-potable pipes must carry indelible labels that remain visible after installation, so no one accidentally ties into the wrong line during future work.³ This is licensed-plumber territory.

Local Permits, Zoning, and HOAs

Municipalities set their own rules on top of the state code. Milwaukee requires no permit as long as your system has no underground collection tank, isn’t connected to the public water supply, doesn’t supply water inside the building, and isn’t used for drinking. Cross any of those lines and you’ll likely need a plumbing or building permit. Milwaukee also requires rain barrels to have a securely covered lid, an inlet screen, and an overflow discharge device sized to handle heavy rain.¹

Zoning ordinances can restrict where you place a barrel or cistern, and larger tanks may need structural review. Rules vary by community, so check with your city or county planning and zoning department before installing anything larger than a basic rain barrel.

HOA Restrictions

If a homeowners’ association governs your property, its covenants likely apply. HOAs commonly regulate the color, material, and placement of rain barrels, and some require a modification request before installation. Wisconsin has no statewide law preventing HOAs from restricting rainwater collection, so those covenants are generally enforceable. Read your governing documents before you buy equipment.

Rebates and Free Rain Barrel Programs

Collecting rainwater can save you money beyond a lower water bill. Several Wisconsin municipalities offer stormwater utility credits or rebates to property owners who install rain barrels. Watertown offers a rain barrel rebate through its stormwater utility program.⁵ The Milwaukee Metropolitan Sewerage District provides free rain barrels at workshops for owner-occupied households.⁶ Check with your local stormwater utility to see whether your community offers similar incentives.

Keeping Your System Compliant and Usable

Standing water breeds mosquitoes, and a properly screened barrel is what separates a legal setup from a nuisance. Window-screen mesh with 18 to 20 openings per inch blocks mosquitoes and most flying insects. Screen every opening, including the overflow outlet.

For water quality, flush sediment from the bottom of your barrel after heavy storms that wash debris off your roof. Larger cisterns should be cleaned and drained at least once a year. Check gutters and downspout filters before each rainy season; leaves and organic matter breaking down in standing water clog spigots and degrade water quality faster than anything else you’ll encounter.

1
City of Milwaukee. Rainwater Harvesting Guidelines for Milwaukee Residents and Property Owners
2
Cornell Law Institute. Wisconsin Administrative Code SPS 382.34
3
Wisconsin State Legislature. Wisconsin Administrative Code Chapter SPS 382 – Design, Construction, Installation, Supervision, Maintenance and Inspection of Plumbing
4
Cornell Law Institute. Wisconsin Administrative Code SPS 382.41
5
City of Watertown. Stormwater Utility Charges and Credits
6
Milwaukee Metropolitan Sewerage District. Everything to Know About Rain Barrels