Gaithersburg, MD Landscaping Rules: Rainwater Harvesting (2026)

Maryland has no restrictions on residential rainwater collection, placing it firmly in the permissive category among states. The state actively encourages rainwater harvesting through tax incentives and rebate programs as part of its Chesapeake Bay Total Maximum Daily Load (TMDL) compliance strategy, which requires significant reductions in stormwater runoff carrying nitrogen, phosphorus, and sediment into the Bay. The Maryland Rain Barrel Tax Credit, established under the Tax-General Article, provides a subtraction modification on state income tax for the cost of purchasing and installing a qualifying rain barrel during the tax year. The credit covers the purchase price of the barrel and basic installation materials. Standard residential rain barrels (typically 55 gallons) require no building, plumbing, or environmental permit and can be connected directly to gutter downspouts using basic fittings. Most rain barrels include an overflow connection that should be directed away from the home's foundation and toward a pervious area of the yard. Larger cistern systems (typically 200 gallons or more) may require a plumbing permit if they connect to indoor plumbing for non-potable uses such as toilet flushing or laundry, and a building permit may be needed for structural cisterns built above or below grade. Montgomery County charges a Water Quality Protection Charge (WQPC) on all properties based on the amount of impervious surface area. This charge funds the county's stormwater management and watershed restoration programs. Property owners who install qualifying on-site stormwater management practices -- including rain barrels, rain gardens, dry wells, permeable pavement, green roofs, and conservation landscaping -- can apply to the county Department of Environmental Protection for a WQPC credit that reduces their annual charge. The county RainScapes Rebate Program provides direct financial incentives of up to $2,500 per residential property for the design and installation of stormwater management practices. Eligible projects include rain barrels (rebate covers a portion of the cost), rain gardens (the most popular project type), conservation landscaping using native plants, permeable pavement for patios and walkways, green roofs, and dry wells. The program provides free site consultations, design guidance, and a list of approved contractors. Applications are accepted year-round and reviewed on a first-come, first-served basis. Gaithersburg residents can also purchase discounted rain barrels through periodic county-sponsored rain barrel sales, typically held in spring.