Upgrading Your Gas Line for a Tankless Water Heater in Upper St. Clair, PA
If you’ve been thinking about switching to a tankless water heater, you’re not alone. Homeowners across Upper St. Clair and the South Hills are making the move for endless hot water, lower energy bills, and the 30% federal tax credit still available on qualifying units. But there’s one thing a lot of contractors don’t tell you upfront — your existing gas line might not be big enough to handle it.
Gas line upgrade in Upper Saint Clair, PA 15241
Why Gas Line Size Matters for Tankless Units
Traditional tank water heaters are low and slow — they heat a 40 or 50 gallon reservoir over time using a relatively modest BTU input. Tankless water heaters work completely differently. They fire on demand at very high BTU rates — often 150,000 to 199,000 BTU/hr — to heat water instantly as it flows through. That means they need a significantly larger gas supply than what was feeding your old tank. If the existing line is undersized, you’ll get error codes, inconsistent water temperature, or the unit simply won’t fire at full capacity.
What the Upgrade Looks Like
When our team came out to this Upper St. Clair home, the existing gas supply line to the water heater location was too small for the new A.O. Smith ProLine XE tankless unit being installed. We ran new, clean square-cut black iron pipe from the main supply to the unit — you can see it in the photo above. Everything is cut clean, threaded tight, and properly supported. We also installed a new quarter-turn ball valve shutoff right at the unit, giving the homeowner a dedicated, easy-to-reach shutoff that meets current code requirements.
The finished installation is neat, professional, and built to last. The PVC concentric vent pipes running up through the floor above handle combustion intake and exhaust in a sealed, direct-vent configuration — no atmospheric drafting, no backdraft risk.
Don’t Let an Undersized Line Kill Your Investment
A tankless water heater is a significant investment — typically $1,500 to $3,000+ installed. Getting the gas supply right from the start protects that investment and ensures the unit performs the way it was designed to. If your contractor isn’t talking to you about gas line sizing before the install, that’s a red flag.
At Pittsburgh Water Heater Solutions, we assess your existing gas supply as part of every tankless installation quote — no surprises, no shortcuts.
Call or text us at (412) 206-9649 for a free estimate.
Areas We Serve Near Upper St. Clair:
Upper St. Clair, Bethel Park, Mt. Lebanon, Peters Township, McMurray, Canonsburg, Cecil Township, South Park, Library, Venetia, Finleyville, Bridgeville, Carnegie, Castle Shannon, Brentwood, and throughout Allegheny and Washington County.