Carnation DADU Water and Sewer: Do You Need a New Meter?
Carnation’s ADU FAQ says an ADU does not automatically need its own water meter. It also describes a connection-charge condition where water and sewer use the primary home’s service line without a new meter. Get the actual service arrangement approved before budgeting around that condition.
Sources checked November 5, 2026. Confirm the requirements for your parcel with its permitting authority.
What does the published guidance say about a separate meter?
The city FAQ states that an ADU does not have to have a separate water meter. Its fee section says no general facilities charge applies when both services can use the primary home’s service line and no new water meter is required.
That is a conditional service outcome. It does not mean every site can share its existing connection or that all public charges disappear. Identify the proposed arrangement in the availability requests and obtain the city’s response for that design.
Official guidance: City of Carnation ADU questions and application steps.
Which documents establish the service approach?
- Water availability certificate for the proposed dwelling.
- Sewer availability certificate for the proposed dwelling.
- A plan locating the existing and proposed service routes.
- A written description of whether a new meter or connection is proposed.
Keep the provider’s response with the building package. If the cottage moves, check whether the approved route still matches the drawing. An availability certificate should be read together with its conditions and the work needed on the property.
How should you compare a shared and a new connection?
| Question | Existing-service option | New-service option |
|---|---|---|
| Public approval | Can the proposed use rely on the existing service? | What certificate and installation approvals apply? |
| Private work | What routing or modification is needed? | What excavation, route and restoration are needed? |
| Budget | Which charges are waived or still payable? | Which meter, connection and other charges apply? |
Use the same cottage design for both comparisons. This makes it easier to identify whether a difference comes from the home itself or from the service work.
Which fee figures should you use?
The linked FAQ is a published city handout, not a current project invoice. Confirm the applicable schedule and the service decision with the city when preparing the estimate. Keep public charges separate from private excavation and installation so the two are not confused.
At a free TimberworX consultation, bring existing utility records and any certificates received. Detailed utility coordination, design and budgeting are paid preconstruction work. The estimate should identify which service scenario it assumes.
A few things to know
Does using an existing service eliminate every permit fee?
No. The FAQ’s condition concerns general facilities charges, not every approval or construction cost.
Should I copy another city’s separate-meter rule into Carnation?
Use Carnation’s service review and the requirements for the actual property.
Keep planning
Carnation DADU Permits: What You Need to Submit
Carnation DADU permit requirements: water and sewer certificates, site plans, parking, walkway and building drawings for a backyard home.
Woodinville DADU Permits: Where to Apply
Find the correct Woodinville DADU permit office, application documents and utility approval path for your property.
Can a DADU use septic or existing utilities?
Check septic capacity, sewer availability, water service and utility routes before committing to a DADU design in King County.