Accessory Dwelling Units (ADUs) — also called granny flats, in-law units, or backyard cottages — have exploded in popularity throughout Riverside County over the past few years. New state laws have made ADUs easier to build, and many Murrieta, Temecula, Menifee, and Perris homeowners are adding them for rental income, multi-generational living, or home office use. Davis Plumbing and Heating Inc. handles all the plumbing and HVAC work for ADU construction and conversions throughout Riverside County.

ADU Plumbing Requirements in California

Every ADU that includes a kitchen, bathroom, or laundry facility needs its own plumbing system — or an approved connection to the main home’s existing system. California law and local Riverside County municipalities require:

  • Separate water and sewer connections (or approved shared connections, depending on local ordinance)
  • Properly sized water supply lines to handle the additional fixtures
  • All drain lines properly sloped and vented per California Plumbing Code
  • Permits for all plumbing work, inspected by the local building department

Plumbing Services for ADUs We Provide

  • New construction rough-in plumbing — Supply lines, drain pipes, and vent stacks installed in new ADU construction before walls close.
  • Garage conversion plumbing — Adding a bathroom and kitchenette to an existing garage requires tapping into existing sewer lines and running new supply lines.
  • Water heater installation for ADUs — Standalone tankless water heaters are ideal for ADUs — they’re space-efficient and provide endless hot water for a second household.
  • Utility connections — Water meter sharing or sub-metering (where required), and sewer line connections to the main lateral.

Heating and Cooling for ADUs

A ductless mini-split heat pump is the ideal climate control solution for most ADUs — it requires no ductwork, provides both heating and cooling, and is highly energy-efficient. Davis Plumbing and Heating installs all major mini-split brands throughout Riverside County.

Permits — Don’t Skip Them

All plumbing and HVAC work in an ADU requires permits in Riverside County. Davis Plumbing handles the permit process for our customers and ensures all work is inspected and code-compliant. This protects your investment and ensures you can legally rent the unit or sell the home without issues.

ADU Plumbing Consultations in Riverside County

Planning an ADU? Davis Plumbing and Heating offers free plumbing consultations for ADU projects in Murrieta, Temecula, Menifee, Perris, Lake Elsinore, Wildomar, San Jacinto, Sun City, and surrounding areas. Call (951) 657-0393 or contact us online to get started.