Yes. Rainwater collection is fully legal in Maryland, with no state limits on how much you can collect from your roof.
What Maryland law says
Maryland places no state-level restrictions on residential rainwater harvesting. You can install as many barrels or cisterns as your property supports, and no permit or registration is required. Encouraged. Some counties, including Howard and Montgomery, offer rebates. As always, check for HOA covenants or local ordinances before installing a larger system.
How much water a Maryland roof can collect
Maryland averages about 44 inches of rain per year. On a typical 1,200 square foot roof at 85% collection efficiency, that works out to roughly 27,900 gallons a year currently running into your storm drain. A single one-inch storm delivers about 635 gallons, enough to fill 13 standard 50-gallon barrels.
Average annual rainfall in Maryland.
Gallons per year from a typical 1,200 sq ft roof.
Approximate annual value at municipal water rates.
Your roof and rainfall will differ; run your exact numbers in the rainwater calculator.
The right setup for Maryland’s climate
At roughly 44 inches of rain a year, Maryland is a wet-climate state; your barrel will refill constantly. Prioritize a sealed, mosquito-proof design and plan the overflow path. A 50-gallon barrel with a diverter that returns excess water to the downspout is the right call.
Rain Wizard 50 + Diverter Kit, reviewed against our independent testing criteria. See all six models side by side.
Common questions
Is it illegal to collect rainwater in Maryland?
Do I need a permit for a rain barrel in Maryland?
Does Maryland offer incentives for rainwater harvesting?
Sources
- Rainplan, 50-State Rainwater Collection Guide (2026)
- State statutes and water agency guidance for Maryland
- NOAA National Centers for Environmental Information, annual precipitation normals
- US EPA WaterSense, Outdoor Water Use fact sheet
Educational content, not legal advice. Laws change; confirm current rules with your state water agency.