Quick answer
Usually, yes. A 199,000 BTU tankless water heater draws about five times the gas of the 40,000 BTU tank it replaces, and the 1/2-inch branch line that fed it cannot carry that much. Many conversions in Burlington, Oakville and Hamilton need a new 3/4-inch or 1-inch run from the meter, and some homes need Enbridge to upsize the meter. Expect the line work to add $400–$1,200 to the install.
Whether a tankless water heater needs a bigger gas line comes down to arithmetic that every TSSA-licensed gas fitter runs before quoting: total connected load, length of pipe from the meter, and the pipe diameter already in the wall. In a lot of Burlington and Oakville homes the answer is that the existing line is fine for the furnace and range but was never meant to feed a burner the size of a tankless.
Why tankless needs so much more gas than a tank
A standard 40- or 50-gallon gas tank has a burner rated around 40,000 BTU per hour, and it runs at that rate for long stretches to slowly reheat the stored water. A whole-home tankless has no storage, so it has to heat water as fast as you use it — a 199,000 BTU input at full fire, with mid-size units around 150,000–180,000 BTU. The unit modulates down when demand is small, but the gas piping must be sized for the moment everything is on.
Pipe capacity falls quickly with length and diameter. The sizing tables in CSA B149.1, the gas installation code Ontario enforces through the TSSA, are built on exactly those two variables. A 1/2-inch line that comfortably carried 40,000 BTU across a basement will not deliver 199,000 BTU over the same run at the pressure the appliance needs, and a starved burner means error codes, lukewarm water and a unit that drops out whenever the furnace fires.
How a gas fitter decides if the line is big enough
- Add up every gas appliance: furnace (often 60,000–100,000 BTU in a typical detached home), range, dryer, fireplace, barbecue stub and the new tankless. That total is what the meter and the main trunk line must carry.
- Measure the developed length from the meter to the farthest appliance, including fittings. A meter at the front of a 1970s–90s two-storey and a mechanical room at the back can be a 20-metre run before any branches.
- Check the system pressure. Older homes run a low-pressure system (about 7 inches of water column) throughout. Some 2000s-plus builds were piped as 2 psi systems with a pounds-to-inches regulator near the appliances, which lets smaller pipe carry far more gas; if your Alton Village or Orchard home has one, the existing line sometimes passes without change.
- Read the tables. If the 1/2-inch or 3/4-inch line cannot carry the total at that length, the fix is a new dedicated run — typically 3/4-inch or 1-inch black iron, or CSST flexible stainless tubing — straight from the meter to the tankless.
Does Enbridge need to change the meter?
Sometimes. A residential meter and its regulator are rated for a maximum flow, and adding a 199,000 BTU appliance to a house that already has a big furnace, a gas range, a dryer and a fireplace can push the total past what the meter delivers. In that case the contractor submits the load to Enbridge Gas and they swap the meter for a higher-capacity one; the house piping is our side of the meter, the meter itself is theirs. This shows up more in larger Millcroft and Glen Abbey homes than in a 1950s Aldershot bungalow with a furnace and a tank.
What upsizing a gas line costs
When the existing line does not pass, upsizing the run adds $400–$1,200 to a tankless conversion, depending on the distance and how much finished ceiling has to be opened. It is a normal line item in a professional quote, not a surprise at the end. A conversion that includes this work still lands in the $3,500–$6,500 range, with the most common 199,000 BTU Rinnai or Navien install at $4,200–$5,000. Our gas line installation page and tankless cost guide break out the pieces, and how much gas line installation costs covers runs for ranges and barbecues too.
Can I skip the gas line work?
Not safely, and not legally. In Ontario, gas piping must be installed by a TSSA-licensed gas technician, and an undersized line is not a cosmetic problem: a burner starved of gas runs poorly and can soot up the heat exchanger. Two honest alternatives exist if the line work is expensive in your house. A smaller 150,000–160,000 BTU unit may fit the existing pipe in a one-bathroom home, and a power-vent tank keeps the gas load close to what you have now while still moving the exhaust out through a side wall.
ZK Mechanical runs the load calculation on every tankless quote and includes the line work in the written price before anything is cut. If you are in Burlington, Oakville, Hamilton or the wider GTA and want to know whether your gas line passes, start with our tankless water heater service or ask for a free assessment.