Commercial Water Heater Repair & Installation in St. Louis
No hot water closes restaurants, clinics, and locker rooms. Legacy Plumbing services and replaces high-volume tank, tankless, and recirculating water heating systems across the St. Louis metro with minimal downtime.
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Commercial Water Heater Repair and Installation
Commercial water heater repair and installation covers the equipment that makes hot water for a whole building: high-volume storage tanks, commercial tankless water heaters, and the recirculation, mixing and safety valves that deliver it at the right temperature. Repair often starts with descaling, anode replacement, combustion tuning or a failed valve. When a unit is leaking from the tank, undersized or failing repeatedly, we size a replacement to the building's real peak demand and compare tank and tankless options before you decide.
Hot water is critical for restaurants and commercial kitchens, healthcare and dental offices, multifamily buildings, schools, industrial facilities and property managers who answer tenant calls when it runs out. We service equipment we didn't install and handle the permit on replacements.
Legacy Plumbing serves St. Louis City, St. Louis County, St. Charles County and Jefferson County from our O'Fallon, MO shop, and has since 1996, with UA Local 562 crews. Service is scheduled Monday–Friday, 7am–4pm.
Related: Commercial Service & Repair · Preventive Maintenance Plans · Backflow Testing & Certification · commercial plumbing contractors in St. Louis
Service areas: St. Louis · St. Charles County · Jefferson County
Water Heating Systems We Handle
Sized to real demand, vented to code, and installed so the next service call is easy.
High-Volume Tank Heaters
Gas and electric commercial tanks, storage tanks, and multi-unit banks sized to peak demand.
Tankless & Condensing Systems
Rack-mounted condensing tankless installs with cascade controls, proper venting, and condensate neutralization.
Recirculation Systems
Pumps, aquastats, balancing valves, and timers so hot water arrives fast without wasting energy.
Mixing & Safety Valves
Thermostatic mixing valves, T&P relief, expansion tanks, and scald protection to code.
Scheduled Replacement
Replacement service scheduled Mon–Fri 7am–4pm, with temporary hot water arranged where the operation can't wait.
Scale & Efficiency Service
Descaling, anode replacement, and combustion tuning that extend life and cut gas spend.
Commercial Water Heater Types
The right system depends on peak demand, available space and fuel. Start with our sizing calculator, then we confirm the numbers on site.
Tank Water Heaters
Gas and electric commercial tanks for high simultaneous draw and simpler controls.
Tankless Systems
Rack-mounted tankless units where footprint and continuous demand matter most.
Boilers with Indirect Storage
Boiler-fed indirect storage tanks for buildings with large, steady hot water loads.
High-Efficiency Condensing
Condensing units with proper venting and condensate neutralization to cut gas use.
Planned Replacement vs. Waiting for a Failure
Our service hours are Mon–Fri 7am–4pm, so the best replacement is one you schedule. Planning ahead lets us size the unit, order equipment and arrange temporary hot water before the old heater quits.
Capacity
Peak demand sets the tank size or input rating, not the nameplate on the old unit.
Venting
Switching to condensing or tankless can change venting materials and routing.
Gas or Electric
Fuel type affects equipment choice, gas piping and electrical work.
Access
Rigging the old unit out and the new one in depends on the mechanical room.
Permit
Replacement is generally permitted through the local building department.
How It Works
Load Sizing
We calculate real peak demand instead of matching the nameplate on a unit that was undersized to begin with.
Equipment & Options
Tank vs. tankless comparison with install cost, gas usage, footprint, and expected life for each.
Rig & Install
Old unit removed, new equipment rigged in, gas, water, venting, and controls tied in and permitted.
Start-Up & Documentation
Combustion testing, temperature verification, and an O&M package with warranty registration.
Commercial Water Heaters FAQ
What are the signs a commercial water heater needs repair?
Running out of hot water at peak demand, slow recovery, temperature swings, leaks at the tank or fittings, a relief valve that discharges, or scale buildup. Commercial water heater repair often starts with descaling, anode replacement, combustion tuning or replacing a mixing or safety valve.
When should a commercial water heater be replaced instead of repaired?
Replacement makes sense when the unit is leaking from the tank, undersized for real peak demand, or repeatedly failing. We calculate the building's actual demand and compare tank and tankless options with cost, gas usage, footprint and expected life before you decide on a replacement.
Is a commercial tankless water heater a good choice?
Tankless wins on footprint, efficiency and continuous demand, while storage tanks win on high simultaneous draw and lower up-front cost. We size both options for your building and show you the numbers before you decide, so the choice is based on how the building actually uses hot water.
Do I need a permit to replace a commercial water heater?
Generally yes. Commercial water heater replacements are usually permitted through the local building department, and Legacy Plumbing handles the permit as part of the job. Capacity, venting, fuel type and mechanical-room access also affect the scope, so we price the work after a site visit.
Do you repair commercial water heaters you didn't install?
Yes. We service all major commercial water heater brands, including equipment another contractor installed, and can add the unit to a scheduled maintenance plan. Call 636-978-0120 Monday–Friday, 7am–4pm to schedule repair anywhere in St. Louis, St. Charles or Jefferson County.
Related reading
For examples of this work, see Facility Water Heater & Backflow Program (Regional Portfolio).
Commercial Water Heaters Across the St. Louis Metro
Restaurants on The Hill, dental groups in Kirkwood, schools in Francis Howell and Fort Zumwalt, and locker rooms in Chesterfield and Wentzville all live and die on hot water availability.
We stock and install commercial water heating across the St. Louis metro, with scheduled service from 7am–4pm Mon–Fri when a unit goes down.
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
Water Heater Failing at Your Facility?
Send the model and building type — we'll size the replacement and quote it.
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