ADU Plumbing Cost across San Diego County
ADU plumbing rough-in and finish runs $12,000-$30,000 in San Diego County, covering the kitchen, bathroom, and water heater connections a full ADU needs, with cost driven mostly by how far the new lines have to run from the existing house connection.
What moves the price
- Distance from the garage to the nearest sewer and water main
- Whether a new water heater is added or the ADU ties into the existing one
- Slab trenching required to run new supply and drain lines
- Full ADU kitchen and bath vs. JADU efficiency kitchen, with sanitation shared or separate
What's included
- Supply and drain line extension to the converted space
- Kitchen and bathroom rough-in
- Fixture installation and finish plumbing
- Water heater installation or connection
- Permit-required plumbing inspections
Common questions
Why does plumbing distance matter so much for cost?
Every additional foot of new supply and drain line means more slab trenching, which is disruptive and labor-intensive. A detached garage far from the house connection point costs meaningfully more to plumb than an attached garage next to an existing bathroom wall.
Does a JADU need less plumbing than a full ADU?
Yes. California JADU law allows sharing the main home's bathroom, which can eliminate the need for a new bathroom rough-in entirely, cutting plumbing cost significantly compared to a full ADU.
Can the ADU share the main home's water heater?
It depends on the existing water heater's capacity and distance. A tankless water heater dedicated to the ADU is common when the existing unit cannot support the added demand or the distance is too far for adequate hot water delivery.
Need a written plumbing cost for your project?
Insured local crews across San Diego County put the scope in writing.