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San Ramon, Dublin & Pleasanton · ADU Plumbing Specialists

Complete ADU plumbing— considerations for your backyard oasis.

An Accessory Dwelling Unit (ADU) adds valuable living space to your property. Our experienced and licensed plumbers specialize in designing, installing, and maintaining code-compliant water, sewer, and gas systems for backyard cottages, garage conversions, and detached ADUs.

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24/7 responseReach the team whenever a plumbing problem hits
Licensed • Bonded • InsuredCalifornia License #1109508
Workmanship guaranteeWork backed by Prime Time Plumbing
Crews clean up before they leave— reviewers consistently mention it
5.0 on GoogleBased on 66+ customer reviews
Your Backyard Addition Experts

Prime Time Plumbing: Your ADU Plumbing Specialists.

At Prime Time Plumbing, we understand the unique challenges of plumbing for ADUs. Our experienced and licensed plumbers specialize in designing, installing, and maintaining plumbing systems for these backyard additions. We’ll work closely with you to ensure your ADU plumbing meets all code requirements and functions flawlessly for years to come.

DFU + Meter
Engineered Utility Tie-Ins We calculate exact Drainage Fixture Units (DFUs), sewer lateral slope, and water meter distance so your ADU has full pressure and zero drainage issues.
Underground water, sewer, and gas trenching for a backyard ADU project.
Underground water, sewer, and gas trenching for a backyard ADU project.
What’s included

Specialized ADU Services

Every installation, inspection, and repair is performed by our licensed, background-checked Tri-Valley plumbing crew.

Underground ADU slab-on-grade plumbing rough-in by Prime Time Plumbing
Foundation Systems

ADU Plumbing Systems: Slab-on-Grade vs. Crawlspace

Before you break ground, it’s crucial to understand how the type of foundation you choose for your ADU will significantly impact the plumbing system design, material selection, and future maintenance access:

  • Slab-on-Grade: Eliminates the need for a crawlspace. Plumbing pipes are run beneath the concrete slab, requiring careful planning, sleeving, and insulation to prevent freezing—with PEX tubing as a top choice for flexibility and freeze resistance
  • Crawlspace: Offers easier access to plumbing for future repairs and maintenance. Pipes run beneath the floor joists for greater placement flexibility, paired with proper insulation and vapor barriers to prevent moisture issues
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ADU sewer lateral connection trench by Prime Time Plumbing
Main Line Connection

Sewer Lateral Work: Connecting to the Main Line

The sewer lateral is the underground pipe that carries wastewater from your property to the municipal main sewer line. When building an ADU, our team evaluates and manages all three critical lateral factors:

  • Sewer Line Availability: We inspect your existing sewer line to verify if it has sufficient depth, grade slope, and capacity to handle the additional waste from the ADU
  • Tapping into the Main Line: Connecting your ADU to the main sewer line or property lateral with full permitting, cleanouts, and code-compliant fittings
  • Navigating Sewer Impact Fees & Agencies: Helping you navigate local water and sanitary district requirements and compliance inspections
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Finished ADU bathroom vanity and shower fixtures by Prime Time Plumbing
Water, Gas & Fixtures

DFU Pipe Sizing, Water Meter Distance & Finish Trim

While many ADU builders simply branch off the main house’s water and sewer pipes, overlooking Drainage Fixture Units (DFUs) or the distance between the ADU and the main water meter can cause low water pressure or sewer backups. We engineer the entire system from utility tie-in to final kitchen and bath fixtures.

  • Precision DFU calculations to determine whether existing house lines need upsizing
  • Water meter distance & pressure-loss calculations for long backyard trench runs
  • Dedicated compact tankless water heaters (exterior or recessed) for the ADU
  • Complete ADU kitchen, bathroom & laundry rough-in and finish fixture installation
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Materials & Standards

Complete ADU Plumbing Scope—Start to Finish

Join us at Prime Time Plumbing, where expertise meets excellence, and let us take care of all your ADU plumbing needs.

Slab-on-Grade ADU Plumbing

Sub-slab DWV layout, protective pipe sleeving through footings, and insulated PEX-A water manifolds.

Crawlspace & Garage Conversion ADUs

Under-joist suspended piping, structural grade-beam coring, and compact wet-wall layouts that maximize living space.

Sewer Lateral & Ejector Systems

Gravity sewer connections to the main lateral, or sealed sewage ejector pump basins when the ADU sits lower than the street main.

Water & Gas Utility Trenching

Single-trench or separated utility runs for water, natural gas (poly pipe), and sewer from the main house or street meter.

Space-Saving Tankless Water Heaters

Exterior wall-mounted tankless units that free up valuable interior closet space inside your ADU.

Permits & Agency Compliance

Full support with local Tri-Valley building departments and water/sanitary districts from rough-in test to final sign-off.

Full-service plumbing

Explore All 6 Plumbing Services

One licensed Tri-Valley team for water, sewer, remodels, gas, new construction, and ADU plumbing.

Water Systems & Water Heaters

Water Systems & Water Heaters

Expert water line repair, tankless & tank water heaters, water softeners, whole-home filtration, and shower/shut-off valves in San Ramon, Dublin & Pleasanton.

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Drain & Sewer Specialists

Drain & Sewer Specialists

Compliant sewer lateral replacement, HD sewer camera inspections, backwater valves, cast iron/PVC/ABS/clay/Fuse Seal repiping & Certificates of Compliance in San Ramon, Dublin & Pleasanton.

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Repairs & Custom Remodels

Repairs & Custom Remodels

Luxury bathroom and kitchen plumbing remodels, freestanding tubs, custom showers, double vanities, rough-in to final fixtures, and 24/7 plumbing repairs in San Ramon, Dublin & Pleasanton.

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Licensed Gas Line Specialists

Licensed Gas Line Specialists

Licensed gas plumbing in San Ramon, Dublin & Pleasanton: MegaPress, Black Iron & Poly underground gas lines, fire pits, outdoor kitchens, pressure testing & leak repair.

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New Construction Plumbing

New Construction Plumbing

Complete new construction plumbing in San Ramon, Dublin & Pleasanton: custom homes, ADU builds, slab & crawlspace rough-ins, DFU pipe sizing & water meter calculations.

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ADU Plumbing Specialists
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ADU Plumbing Specialists

Specialized ADU plumbing in San Ramon, Dublin & Pleasanton: slab-on-grade vs crawlspace systems, sewer lateral tie-ins, DFU sizing, water meter upsizing & permits.

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Local service area

Proudly serving San Ramon, Dublin, Pleasanton & Surrounding Areas.

Based at 2010 Crow Canyon Place in San Ramon and serving homeowners, businesses, and builders across the Tri-Valley and East Bay.

San Ramon
Dublin
Pleasanton
Common questions

ADU Service FAQs.

Can my ADU connect to my main house’s existing sewer and water lines?

In many cases yes, provided the existing pipes have enough capacity (Drainage Fixture Units / DFUs), proper slope depth for gravity drainage, and sufficient water meter pressure for the added distance. We inspect and calculate all of these before trenching.

Which is better for ADU plumbing: slab-on-grade or crawlspace?

Both work great when properly engineered. Slab-on-grade is very popular and uses durable sub-slab piping and PEX tubing, while a crawlspace foundation makes future access or layout adjustments under the floor joists easier.

What if my backyard ADU sits lower than the main sewer line at the street?

If gravity drainage isn’t possible due to elevation, we install a quiet, sealed commercial-grade sewage ejector pump system that pumps wastewater up to the main sewer lateral reliably.

Do you handle the plumbing rough-in and final fixtures for garage conversion ADUs?

Yes! We saw-cut the existing garage slab cleanly, tie into the sewer/water/gas systems, run new bathroom, kitchen, and laundry lines, pass city inspection, and install all final fixtures.

Get the plumbing problem off your plate.

Start with a free quote. Prime Time Plumbing will take it from there.

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