Quick answer: Do not assume a Maryland ADU either requires a separate water or sewer connection or has a statewide right to share the existing one. Ask the serving utility and permitting authority to confirm capacity, connection design, meter arrangements and charges for your property.
Correction — October 10, 2026: An earlier version of this guide incorrectly described proposed utility provisions as enacted HB 1466 protections. The separate-connection limitation, connection-fee prohibition and shared-water-meter election in proposed §4-507 were deleted before enactment. They are shown struck through on page 9 of Chapter 197. This guide has been corrected; those deleted provisions are not a basis for assuming a fee waiver or shared-service entitlement.
What Maryland’s enacted ADU law establishes
HB 1466 became Chapter 197 of the 2025 Laws of Maryland, effective October 1, 2025. Its local-law adoption deadline was October 1, 2026. The current Land Use §4-504 requires ADU construction to meet public-health, safety and welfare standards, including relevant building codes and adequate-public-facilities provisions. It does not contain the deleted §4-507 utility guarantees.
The 2026 HB 1538 record also describes proposed utility-fee and shared-service changes, but the official record checked October 10, 2026 does not show enactment. A proposed effective date is not proof a bill became law.
Confirm the actual utility arrangement before design
Identify the water and sewer providers separately, then describe the proposed ADU type, location, sleeping capacity and expected use. Request a written answer identifying:
- whether the existing service has adequate capacity;
- whether shared or separate service connections and meters are accepted or required;
- the applicable utility rule, permit process and drawings;
- connection, capacity, permit, inspection and ongoing service charges, itemized separately; and
- who will complete the work and which approvals are needed before construction.
Adequate capacity is an important engineering and utility-review question. It does not, by itself, establish a statewide fee exemption or right to a shared connection. Keep unresolved utility work visible in the budget until the provider confirms the scope and charges.
What about private wells and septic systems?
The statewide utility protections should not be read as automatic approval for a private septic system or well to serve an additional dwelling unit. Septic capacity, bedroom count, reserve area and well requirements can become major feasibility constraints.
We cover those issues separately in our Maryland ADU septic and well guide.
Does an ADU need a separate electric meter?
Do not assume the statewide water-meter rule answers the electricity question. HB 1466’s specific shared-meter language concerns water supplied by a utility. Electrical service design can depend on the serving utility, the existing panel and service capacity, the ADU design, electrical code requirements and local permitting.
For planning purposes, ask an electrician whether the existing service can support the additional load before treating a service upgrade or second meter as either required or unnecessary.
What homeowners should verify before budgeting
- Is the property on public water and sewer, or private well and septic?
- Who is the actual water/sewer utility or authority?
- Does the existing connection have adequate capacity for the proposed ADU?
- Will the plumbing design integrate the ADU into the existing service?
- Does the electrical service or panel need an upgrade?
- Are there utility-related permit, inspection or capacity-review charges that are different from a prohibited connection fee?
- What does the county or municipality’s current ADU ordinance require?
Maryland is still in the 2026 local implementation period
HB 1466 is enacted statewide law, but Maryland jurisdictions have until October 1, 2026 to adopt the required local ADU legislation. That makes the distinction between statewide protections and current local procedures especially important in 2026.
Start with our Maryland ADU Rules Tracker and Maryland ADU Jurisdiction Finder to identify the rules and agency that apply to your property.
Bottom line
For a Maryland ADU on public water or sewer, do not start with the assumption that you must buy a completely separate connection. Maryland law protects the use of an adequate existing connection and allows a shared water meter. Metering is separate from whether the unit receives its own mailing or emergency-response address; see the Maryland ADU address, mailbox and 911 guide. But the word adequate matters: confirm capacity and the current local process before finalizing your ADU budget or design.
Primary source
This guide is based primarily on Maryland HB 1466 / Chapter 197 (2025), including the enacted utility provisions. Because local implementation is evolving during 2026, verify property-specific requirements with the applicable county, municipality, utility and permitting authority.
Maryland ADU Guide is an independent homeowner planning resource and is not a government agency, utility, engineering firm or law firm. This article is general information, not legal or engineering advice.
What to do next
Start by finding the office that reviews your property. A mailing city or a county guide does not establish your parcel’s authority.
- Find Who Reviews My Property.
- Obtain your parcel identifier, survey, floor plans and utility records.
- Ask the reviewing office which current rules, supporting documents and approvals apply.
- Continue to your planning workspace.
Enable JavaScript to prepare a downloadable next-step brief. Planning guidance is not permit approval.