Pull a SPU Water Availability inquiry

Why this is the cheapest move you'll make

Seattle Public Utilities (SPU) issues a Water Availability Certificate that tells you whether the water main on your street can serve a new unit. Free inquiry, written answer in 1-3 weeks.

For most parcels the answer comes back "available, no conditions" or "available with a small upgrade." On a small number of streets — usually older, smaller mains — SPU says service requires a main upgrade. A 2023 Urbanist op-ed documented a Phinney Ridge ADU where the upgrade quote came in around $750,000. That's the tail of the distribution, not the median. The free inquiry tells you which side you're on, and it costs nothing to ask.

How to do it

Email SPU's New Service Connections team or use the Seattle Services Portal. Give them the parcel address and a one-line description of the planned use ("adding a 700 sq ft DADU on existing parcel; one new dwelling unit").

You'll get a letter back in 1-3 weeks. Three possible outcomes:

• Available, no conditions — you're good to go.
• Available with conditions — usually a fire-flow remediation or small upgrade you can budget for.
• Not available without main upgrade — read carefully and book a meeting with SPU before doing anything else.

The one-meter rule

Even when water is available, SPU's standing rule is one domestic water service per parcel. Your DADU shares the existing meter by default. A separate metered service for the cottage is rare and expensive. What most owners do instead: install a private submeter inside the cottage (electrician installs, owner reads, lease reconciles) — no second SPU permit needed.