Accessory Dwelling Unit plumbing requires connecting new water and sewer lines to the primary residence while maintaining proper slope and pressure. You must secure local San Diego permits and ensure the main sewer line has the capacity for increased wastewater volume.

The rough-in phase installs all underground pipes before the concrete foundation is poured, ensuring all utilities meet municipal building codes.

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The Bottom Line for San Diego Homeowners

Adding an ADU or a new room is a massive investment. The plumbing foundation dictates the success of the entire build. You cannot simply attach new pipes to old ones without calculating water pressure and drainage slopes.

If your primary home has aging pipes, you might need repipe services before the ADU can be safely connected. Properly planning the rough-in phase, especially for complex additions like laundry room plumbing, prevents costly tear outs after the drywall is already up.

Key Technical Details

• Verify sewer capacity: The existing main line must handle the combined load of both dwellings.
• Separate metering: Consider installing sub meters to track the ADU water usage independently.
• Trenching requirements: New sewer lines require precise trenching to maintain a quarter inch per foot slope.
• Permit compliance: All rough-in work must pass a municipal inspection before framing begins.

How the Process Works

During the rough-in phase, plumbers dig trenches to lay the foundational sewer and water supply lines. These lines are routed to the exact locations where future sinks, toilets, and showers will sit.

The system is then capped and pressurized with air or water to test for leaks. A city inspector must sign off on this work before the general contractor pours the concrete slab.

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Frequently Asked Questions

Can an ADU share a sewer line with the main house?

Yes, an ADU can typically tie into the main house sewer line, provided the existing pipe is structurally sound and meets current building codes for capacity.

Do I need a separate water heater for an ADU?

Yes, building codes generally require a dedicated water heating source for an ADU to ensure adequate hot water supply.

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Call us at 1-800-388-8149 or Reach out at plumber@plumbtechpros.com