Property feasibility
ADU Utility Connections
An ADU needs the same services as a house: sewer, water, power and usually gas. Where those lines are, how far they must run and what the providers will allow can decide where the unit goes.
Ask a builder what makes one backyard ADU cost more than another on a similar lot, and utilities will be near the top of the answer. A unit near the street with the sewer running past it is a short connection. The same unit at the back of a lot, downhill from the sewer line, is a different project. This page covers the questions that apply to every utility. The detail guides cover ADU sewer and water and ADU electrical service.
What connecting an ADU involves
- Sewer.A line from the unit to the house's lateral or the public main. It usually runs by gravity, so depth and slope matter most. The lateral is the private pipe from the house to the main.
- Water.A branch from the house's service line, sized so both homes have enough flow and pressure.
- Electrical.A feeder from the house's panel, or a larger service if the panel cannot carry the added load.
- Gas.A branch line if the unit uses gas for heat, water heating or cooking. Holladay's utilities page, for example, lists Enbridge Gas.
For an internal or basement ADU, these are mostly changes inside the house. For a detached unit, each is a trench across the yard, and the routes have to work around trees, fences, other utilities and the setbacks.
Sharing the house's services
The Salt Lake City and South Salt Lake ADU handbooks say the same thing: the existing sewer and water service to the property may be used for the ADU, but site conditions and the age and condition of the existing services may require additional work or separate connections. Salt Lake City's handbook lists drain grade and slope as a major up-front issue. In practice, the questions are whether the old lateral is in good enough condition to take more flow, and whether a new line from the unit can reach it with enough fall.
Separate meters, city by city
State law lets a city prohibit a separate utility meter for an internal ADU. Most cities we cover prohibit separate meters for every ADU:
| Jurisdiction | Separate meters for an ADU | Source |
|---|---|---|
| Millcreek | Prohibited. The city's ADU page says secondary meters may be allowed to monitor usage | 18.71.060; city ADU page |
| Salt Lake City | Not addressed in the ADU sources we reviewed; confirm with Public Utilities | ADU Handbook |
| Murray | Prohibited | 17.78.040, 17.78.050 |
| South Salt Lake | Second or separate meters cannot be added | City ADU page |
| Holladay | May not operate on separate meters; the tenant must have unobstructed access to utility connections | 13.14.031 |
| Sandy | Separate utility connections or meters prohibited; private meters behind the primary meters and inside the dwelling may be allowed | 21-11-1 |
| Cottonwood Heights | Prohibited | 19.75.050 |
| Unincorporated county | Internal: not allowed. Detached: allowed if the owner is billed for both | County Code 19.15.140 |
One meter means one bill. If you plan to rent the unit, decide early how utilities will be shared, and whether a private submeter is allowed where you live.
Getting the providers to say yes
Cities increasingly want a provider's confirmation in hand before a permit. Cottonwood Heights asks for will-serve letters from the water and sewer providers for ADUs that involve construction. Unincorporated Salt Lake County will not issue an ADU building permit until the water supplier confirms in writing that the ADU meets its requirements, and it asks for water and sewer availability letters. Millcreek asks anyone adding a building or square footage to contact the utility companies to confirm that service can be provided. Murray's first step is a meeting with Planning that covers utility connection requirements, and South Salt Lake's predevelopment checklist asks for proof of sewer service.
The state is moving the same way. Since October 1, 2026, Utah Code 10-21-304 lets a city prohibit a detached ADU that lacks adequate utility access or where system capacity is insufficient.
Fees that come with connections
State law bars impact fees for an internal ADU within an existing primary dwelling (Utah Code 11-36a-202). There is no matching exemption for detached ADUs. South Salt Lake's handbook says applicable impact fees and utility connection fees apply. Whether a given sewer district or water provider treats an ADU as a new unit is set by that provider, and most have not published an ADU rule. One that has is Mt. Olympus Improvement District, covered on our sewer and water page. Our ADU cost guide explains how these fees fit the budget.
How utilities shape the plan
Utilities are one of the reasons we look at a lot before anyone draws. The sewer connection sets how low the unit's floor can sit and how far back it can go. A long trench across a finished yard adds cost and disturbance. A full electrical panel may mean a service upgrade. Sometimes the answer is to move the unit closer to the existing lines, or to choose an internal ADU instead.
Next steps
Work through the other questions in Can I build an ADU?, then locate where your sewer, water and power enter the house. Our ADU feasibility review traces the likely routes and flags which provider questions to ask first. To start, See What Your Property Can Support.
Questions about ADU utility connections
Can an ADU have its own utility meters?
In most of the cities we cover, no. Millcreek, Murray, South Salt Lake, Holladay, Sandy and Cottonwood Heights all prohibit separate utility meters for an ADU. Millcreek's ADU page and Sandy's code allow a private or secondary meter to track usage in some cases. In unincorporated Salt Lake County, a detached ADU may be separately metered if the owner is billed for both.
Can an ADU share the house's sewer and water lines?
Often, yes. The Salt Lake City and South Salt Lake ADU handbooks both say the existing sewer and water service may be used for the ADU, but that site conditions and the age and condition of the existing services may require additional work or separate connections. The provider for your address has the final say.
Do ADUs pay utility impact fees?
It depends on the ADU type and the provider. State law bars impact fees for an internal ADU built within an existing primary dwelling. There is no matching exemption for detached ADUs, and South Salt Lake's handbook says applicable impact fees and utility connection fees apply. Ask each provider how it counts an ADU.
Who confirms that utilities can serve an ADU?
The providers themselves. Cottonwood Heights asks for will-serve letters from the water and sewer providers when an ADU involves construction, unincorporated Salt Lake County requires written confirmation from the water supplier before a permit, and Millcreek asks applicants for new buildings to confirm with the utility companies that service can be provided.