New Construction & ADU Plumbing in the Las Vegas Valley

New construction plumbing is the full water, drain, waste and vent system for a building that does not exist yet, installed in phases: underground lines before the slab, rough-in inside the framed walls, and trim once finishes are in. ADU and casita plumbing adds a second dwelling to a lot that already has one, which means tying into an existing water service, sewer lateral and often a gas line. The work is permitted and inspected at each phase by the building department for the address.

Plumbing a new building starts before anything is visible. Drain lines rely on fall and venting rather than pressure, so where the waste line can run decides where kitchens and bathrooms sensibly go, and that is far easier to settle on the plans than in the field. On an ADU or casita the questions widen: whether the existing water service and sewer lateral can carry a second dwelling, how the new waste line reaches the main with the slope it needs, and whether a gas appliance means talking to Southwest Gas about meter capacity.

Underground work in the valley often runs into caliche, a cemented calcium-carbonate hardpan that makes trenching slower and costlier and can abrade a pipe laid against it. Lines are bedded and backfill is compacted properly, because poorly compacted fill settles under a pipe over time and pulls it out of grade. Supply lines are sized for real demand, and under the 2024 Uniform Plumbing Code with Southern Nevada Amendments, gas piping under a slab has to be removable without disturbing the slab, so it runs in conduit or a listed system.

Each phase is inspected by the building department for your address before walls close or concrete goes down. If the existing house needs work to support the new unit, Whole-House Repipe or Sewer Line Repair & Replacement can be planned in the same project. Call Active Plumbing at (702) 438-3357 to walk through your plans.

Bathrooms placed where the waste line cannot get the fall it needs without raising a floor or breaking a beam. An existing water service or sewer lateral sized for one dwelling being asked to serve two. Gas appliances planned for an ADU without checking meter capacity with Southwest Gas. Rough-in that lands after the slab is poured or the drywall is hung. Underground lines laid on poorly compacted backfill that later settles and leaves a belly in the drain.

New construction plumbing typically runs $8,000 to $20,000 in the Las Vegas Valley. That is a typical range, not a quote. Square footage, fixture count, the length of the underground run, caliche in the trench, gas piping and any upgrades the existing house needs all move the figure. We can give a general idea on the phone and a written price before work starts. Timelines follow the build: underground before the slab, rough-in after framing, and trim after finishes, each with its own inspection by the building department for your address.

Underground drain and supply lines are laid to grade on proper bedding, with backfill compacted to limit settling. Rough-in covers supply distribution, drain, waste and vent piping, and stub-outs at each fixture, using materials approved under the local plumbing code, with PEX common in new construction. Supply sizing follows the adopted code, including Appendix M, the peak water demand calculator. Fixtures are trimmed to the Southern Nevada Amendments, including WaterSense lavatory faucets, showerheads and toilets, and gas piping under a slab runs in conduit or a listed system. New construction and ADU work uses PEX including Uponor, with Watts valves and regulators.

Call Active Plumbing at (702) 438-3357 with your plans or your build schedule. We will review the layout, flag anything that will cause trouble at inspection, and give you a written price before work starts.