ADU Utilities: Sewer, Water & Power Connections
By Eric Dexter, Owner & Builder ·
A detached ADU is a full, independent home — which means it needs its own connections for sewer, water and power. This utility work is essential, and it's one of the biggest reasons two identical-looking DADUs can cost very different amounts to build. Here's what's involved.
What utilities an ADU needs
- Sewer — a side-sewer connection to the public main (or an approved septic system).
- Water — a supply line, often with its own meter for a rental.
- Power — an electrical service to the unit, either new or extended from the main house.
The side sewer is the wildcard
Connecting to sewer is often the least predictable piece. If the main is close and the run is simple, it's straightforward; if it's far, on a slope, or under existing hardscape, the trenching and restoration add cost. It's exactly the kind of thing a feasibility study catches early — see can I build an ADU on my lot?
Why utilities drive the budget
Utility runs are part of site development — and on a tight or sloped lot they can be a big share of the total. That's why an honest quote prices them up front instead of leaving them out; see our realistic costs page.
Permits
Utility connections require their own permits — side sewer, water and electrical — alongside the building permit. DIGS manages all of it as part of the build; see the DADU permit guide.
We do the utility work in-house
Utilities are one of our core trades, not a subcontractor handoff — which keeps your project coordinated and on schedule. Estimate your build with the cost calculator, or tell us about your lot.
