A tankless water heater heats water on demand — no tank to run out of, no standby energy loss keeping 40–50 gallons hot around the clock. STL Plumbing Pros installs gas and electric tankless units with proper gas line sizing, venting, and condensate drainage. We size the unit to your household's actual demand so you get consistent hot water at every fixture.
Benefits of Going Tankless
Endless hot water — heats on demand, never runs out during back-to-back showers.
24–34% energy savings — no standby heat loss from keeping a tank of water hot 24/7.
15–20 year lifespan — nearly double a traditional tank water heater.
Space savings — wall-mounted units free up floor space in utility rooms and basements.
Reduced water damage risk — no 40–50 gallon tank that can leak or fail catastrophically.
Gas vs. Electric Tankless
Gas Tankless
Higher flow rates (8–10 GPM), ideal for whole-house applications. Requires proper gas line sizing (typically 3/4") and dedicated venting. Most St. Louis homes with existing gas water heaters are good candidates for gas tankless conversion.
Electric Tankless
Lower flow rates (3–5 GPM), best for point-of-use applications or smaller households. No venting required but may need an electrical panel upgrade. Lower upfront cost than gas units.
Our Installation Process
Site Evaluation & Sizing
We assess your household's hot water demand, inspect the gas line size, evaluate venting options, and recommend the right unit. You get a complete quote before any work begins.
Installation
Remove the old tank unit, mount the new tankless, connect gas (with line upgrade if needed), install venting and condensate drain, connect water supply and hot water distribution.
Testing & Walkthrough
We test hot water delivery at every fixture, verify gas connections with a leak check, confirm venting operates correctly, and walk you through the unit's controls and maintenance schedule.
Tankless Water Heater Pricing
| Service | Price | Details |
|---|---|---|
| Gas tankless water heater (supply & install) | $3,000–$5,500 | Includes unit, gas line sizing, venting, and condensate drain. |
| Electric tankless water heater (supply & install) | $1,800–$3,500 | May require electrical panel upgrade — electrician coordination included. |
| Tank-to-tankless conversion | $4,000–$6,500 | Includes gas line upgrade, new venting, and removal of old tank unit. |
| Annual tankless flush service | $150–$250 | Descaling with food-grade vinegar to maintain efficiency. |
Why Choose STL Plumbing Pros?
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Properly Sized, Every Time
We size the unit to your actual demand — not the minimum. An undersized tankless unit delivers lukewarm water during peak use.
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Gas Line Expertise
Tankless installations often require gas line upgrades. We handle the complete gas line work — no need to coordinate a separate contractor.
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Maintenance Plans Available
Annual tankless flushing is essential in St. Louis's water conditions. We offer maintenance plans to keep your unit running at peak efficiency.
What Our Customers Say
"Switched from a 40-gallon tank to gas tankless. Never running out of hot water is life-changing. Installation was clean and professional."
"They properly sized the unit for our 3-bathroom house and upgraded the gas line. Everything works perfectly — consistent hot water at every fixture."
"Appreciated the honest assessment. They explained that for our small household, a traditional tank might be more cost-effective. No upselling. We went tankless anyway for the space savings."