Tankless Water Heater Gas Line Upgrades in Fort Worth, TX

Why a tankless burner needs so much more gas

A tank heats its water slowly and stores it, so a small burner does the job: a typical 40- or 50-gallon gas tank is rated around 35,000 to 50,000 BTU per hour. A tankless unit heats water while it flows, from cold to shower temperature in seconds. Federal efficiency programs count a gas tankless heater as residential below 200,000 BTU per hour, and most whole-house models run roughly 140,000 to 199,000. Natural gas carries about 1,000 BTU per cubic foot, so a 199,000 BTU unit at full fire pulls close to 200 cubic feet an hour.

Sizing the line by length and total demand

Pipe sizing here follows the 2021 editions of the International Fuel Gas Code and the International Residential Code, as Fort Worth amended them. The standard low-pressure table in those codes for steel pipe shows capacity falling as runs get longer:

• Half-inch: about 118 cubic feet per hour at 20 feet and 95 at 30 feet.
• Three-quarter-inch: about 247 at 20 feet and 199 at 30 feet.
• One-inch: about 466 at 20 feet and 374 at 30 feet.

So a half-inch branch may deliver half what a big tankless unit wants. The code adds every appliance's full input as if all run at once, and its longest-length method sizes each section from the longest run, meter to farthest outlet. The furnace, range and dryer share the first stretch off the meter, so that section often has to grow too. A starved line shows up as error codes when a second shower opens, or water swinging between hot and lukewarm.

Your meter and Atmos Energy

Atmos Energy owns the meter; the piping from it to your appliances is yours. A meter set for a furnace, range and tank heater may not handle another 150,000 BTU or so, and only Atmos can change it. If totals look tight, we flag it during sizing so you can contact Atmos early.

Venting and condensate drain changes

A standard gas tank vents up a metal flue on natural draft. A tankless heater pushes its exhaust out with a fan, and the fuel gas code leaves its vent design to the manufacturer's instructions, so expect new vent pipe and routing.

• Non-condensing models typically use stainless steel vent pipe built for hot exhaust.
• Condensing models wring extra heat from the exhaust with a second heat exchanger, cooling it enough for plastic vent pipe such as PVC.

Fort Worth's code amendments keep water heaters out of residential attics but make an exception for tankless units, and the city's gas inspection checklist wants any attic or roof gas valve approved for temperatures above 145 degrees.

Condensate drain on condensing models

That cooler exhaust condenses into water that can be acidic. It has to run in corrosion-resistant pipe, sloped downhill, to an approved drain, and Fort Worth's amendment sets a three-quarter-inch minimum drain size. Some manufacturers require a neutralizer, and a line through a garage or attic needs a route that won't freeze.

Permit, pressure test and inspection

Fort Worth requires a plumbing permit to change or install a water heater, and gas piping, the gas test and condensate drains are line items on the city's plumbing permit application with Development Services. The usual sequence:

1. Model first. Share the make and model so sizing starts from its real input rating.
2. Measure. A plumber checks the meter, traces the pipe and measures the longest run.
3. Rough-in. New pipe goes in with a shut-off valve at the heater and a sediment tee after it; inspectors check for both.
4. Pressure test. The capped piping is held under test on a diaphragm gauge, and Fort Worth's amendment sets a 15-minute minimum. See gas pressure test.
5. Hook-up. If Atmos shut off the meter, it restores service after the city's gas release. Then the heater is connected, purged, leak-checked and run at full flow.

Part of your water heater installation

Water connections, the relief valve and removal of the old tank are covered on our water heater installation page; a tankless unit also needs service valves for descaling and an outlet for its fan. Compare tankless with other types on the water heaters hub. Offers, with terms on the coupons page: $150 off a new water heater, $50 off for new customers, and 10% off for seniors, military and first responders.

Plumber 24 Fort Worth holds Texas plumbing license # M-27587 and works from Riverside across Fort Worth, Haltom City, North Richland Hills and other nearby towns. In older Riverside, Oakhurst and Six Points houses the gas piping predates tankless heaters, so every section gets checked.

Tankless gas line questions

Talk through your tankless gas line

Call (817) 755-5621 and tell us which tankless unit you have your eye on. We'll check the meter, pipe and vent route. Installs are booked at a time that suits you. Smell gas? Leave the building first, don't flip switches or light anything, call 911 or Atmos Energy from outside, then call us at any hour and we send our on-call plumber right away.

Office hours 8 AM–11 PM daily · 24/7 emergency service