Quick answer: A Maryland ADU does not automatically need its own water connection or water meter. Under Maryland’s statewide ADU law, a utility may not require a new or separate water or sewer connection when the existing connection serving the primary home has adequate capacity for the ADU. When the ADU is integrated into an adequate existing connection, the utility may not charge a connection fee associated with that integration. A person developing an ADU may also elect to use a water meter shared with the primary dwelling.
That does not mean utilities can be ignored. Capacity, septic or well constraints, plumbing design, electrical service and local permitting can still affect whether a particular property is ready for an ADU.
What Maryland’s statewide ADU law actually says
Maryland enacted HB 1466 as Chapter 197 in 2025. The law took effect October 1, 2025 and requires covered counties and municipalities to adopt local ADU legislation by October 1, 2026. The law includes specific protections concerning water and sewer connections for ADUs.
1. A separate connection is not automatically required
If the primary dwelling’s existing water or sewer connection has adequate capacity to serve the ADU, the utility may not require a new or separate connection solely because the ADU is being added.
2. Integration should not trigger a connection fee
When an ADU is integrated into an existing connection that has adequate capacity, the statewide law prohibits a utility from charging a connection fee associated with that integration.
3. A shared water meter is allowed
A person developing an ADU may elect to use a water meter shared with the primary dwelling to track water delivered by a utility. Maryland law therefore does not create a blanket requirement for every ADU to receive a separate water meter.
The key phrase is “adequate capacity”
This is the part homeowners should not skip. The protection against a separate water or sewer connection depends on the existing connection having adequate capacity. A property-specific review may therefore still be necessary.
Before assuming your current service can handle an ADU, verify the applicable utility provider, available water and sewer capacity, required plumbing plans and any local permit conditions. For properties using private wells or septic systems, the analysis is different and may depend on health-department requirements and the capacity of the existing system.
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. 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.
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