New Commercial Plumbing System Installation in St. Louis, MO
Legacy Plumbing installs complete plumbing systems for new commercial buildings, additions, and expansions across the St. Louis metro — underground rough-in through final trim, inspected and turned over on schedule.
Request a New System Bid
Tell us scope, schedule, and site address. We reply within one business day.
What a Full System Install Includes
One licensed contractor for every wet system in the building, coordinated with your GC's schedule and the local AHJ.
Domestic Water Distribution
Copper, PEX, and press-fit mains, risers, and branch piping sized to fixture-unit load with insulation and hangers to spec.
Sanitary & Vent Systems
Underslab and above-ground DWV in cast iron and PVC, tested and inspected before cover and again at top-out.
Storm & Roof Drainage
Roof drains, overflow, and interior storm leaders tied to site storm structures with proper slope and cleanouts.
Natural Gas Piping
Black iron and CSST gas distribution for boilers, water heaters, rooftop units, and kitchen equipment with pressure testing.
Fixtures & Equipment Setting
Commercial fixtures, carriers, water heaters, pumps, mixing valves, and specialty equipment set and started up.
Testing, Inspection & Turnover
Chlorination, pressure and hydrostatic testing, AHJ inspections, and O&M documentation delivered at closeout.
How We Deliver a New System
Takeoff & Bid
We price from your plan set or design intent, flag long-lead fixtures, and identify value-engineering options up front.
Coordination & Submittals
Shop drawings, fixture submittals, and BIM coordination with mechanical, electrical, and structural before anything is fabricated.
Underground & Rough-In
Underslab DWV and water go in ahead of the pour, then above-ground rough-in sequenced against framing and drywall.
Trim, Test & Close Out
Fixtures set, systems tested and chlorinated, inspections passed, and a documented turnover package handed to ownership.
New Plumbing System FAQ
Do you install plumbing systems for additions to occupied buildings?
Yes. We phase tie-ins and shutdowns around your operating hours so the existing building keeps water and drainage while the addition is built out.
Can you work from design intent instead of a finished plan set?
Yes. Our design/build team can develop the plumbing design, stamp it through an engineer of record, and carry it through permit and install.
What areas do you install new systems in?
The entire St. Louis metro — St. Charles, St. Louis City and County, Jefferson, Franklin, Lincoln, and Warren counties, plus a 2-hour radius from O'Fallon, MO.
New Plumbing Systems Across the St. Louis Metro
New plumbing systems have to satisfy whichever AHJ holds the permit — and in Greater St. Louis that changes block to block. We install to the adopted code in St. Louis City, St. Louis County, St. Charles County, and the Jefferson County municipalities every week.
From a Chesterfield office core to a Wentzville warehouse and a Hazelwood clinic, our crews mobilize from O'Fallon and stay staffed through certificate of occupancy.
Don't see your city below? We work the entire metro and a 2-hour radius from O'Fallon, MO. View full service area →
St. Charles County
Warren County
Planning a New Plumbing System in St. Louis?
Send us your plans or design intent — we'll return a scoped, schedule-aware bid.