Peak demand, not daily consumption
This is the single idea that explains most gas supply surprises, and it is counterintuitive enough that it catches out people who are otherwise well informed.
A gas line is not sized for how much gas you use. It is sized for how much gas could be flowing through it at the busiest single moment, with every connected appliance running simultaneously. That figure is called the connected load, and it is what the pipe diameter and the meter have to satisfy.
So an appliance that uses very little gas over a day can still be a problem, if it draws heavily while it is actually running. A tankless water heater is the classic case: it uses less gas per day than the storage tank it replaces, because it is not keeping a reserve warm around the clock, but while it fires it draws several times the tank's rate.
Add that to a system already carrying a furnace, a range, a dryer and a pool heater and the connected load can exceed what the existing pipe or meter will deliver. Nothing fails dramatically. Things just underperform when several run together.
What it looks like when the supply is short
- A new appliance works perfectly on its own and falters when something else fires.
- Hot water going lukewarm when the furnace kicks in, or vice versa.
- A furnace or heater that short cycles under combined load.
- Yellow, lazy or lifting burner flames where they should be crisp and blue.
- Pilot outages that only happen when other appliances are running.
- An appliance throwing low-pressure or ignition error codes intermittently.
The pattern to notice across all of those is that they are intermittent and correlated. A genuinely faulty appliance misbehaves on its own schedule. A supply problem misbehaves when something else is running, which is why it so often gets misdiagnosed as an appliance fault and why people sometimes replace a perfectly good unit.
The yellow flame item deserves separate attention, because it is not only a performance signal. Incomplete combustion produces carbon monoxide, which has no odour at all. Working carbon monoxide alarms on every level of a building with gas appliances are the practical answer, because they detect what people cannot.
What actually goes into sizing it properly
| Input | Why it matters | Commonly missed |
|---|---|---|
| Every connected appliance's rating | Connected load is the sum, not the biggest | Outdoor kitchens, fire features and generators get forgotten |
| Developed length from the meter | Pressure drops over distance | Long runs to detached structures on large parcels |
| Number of fittings and turns | Each adds equivalent length | Underestimated on complex routing |
| System pressure and allowable drop | Sets the table used for sizing | Assumed rather than confirmed |
| Meter capacity | The supply has to meet the total | Checked last, if at all |
| Future additions | Cheaper to size for now than to redo | Rarely asked about |
Two things large parcels change about sizing
The second and sixth rows are where this area differs from a suburb, and both come down to the size of the parcels.
Run length matters because pressure drops with distance, so the same pipe diameter delivers less at the far end. On properties with detached garages, workshops, barns, well houses and outdoor kitchens, gas runs here are considerably longer than a compact lot would need, and a size that works near the meter may not work out at the far structure.
Future additions matter for the same reason. Upsizing a long buried run across established landscaping is expensive, so being asked what else you might add in the next few years is a sign the person sizing it is thinking properly rather than minimising today's quote.
STUCK ON THIS ONE?
A load calculation before purchase is cheaper than a line upgrade afterward. Call (480) 806-2944 and you will get a range and an arrival window before anyone is dispatched.
The pressure test is where the safety lives
Whatever else happens, a gas system is not returned to service on the basis that the work looked correct. It is tested to hold pressure, and that test is the evidence.
This is the part worth insisting on and worth understanding as a customer. A correctly executed gas job includes a load calculation, pipe sized for the run length, materials appropriate to whether the section is buried, exposed or interior, correct shutoffs and sediment traps at the appliance, and a pressure test before gas returns.
The permit and inspection exist to verify that independently, which is why they are worth wanting rather than avoiding. Arizona sets no statewide code, so the edition depends on your address: the Town of Cave Creek adopts International Codes by reference and moved to the 2024 family and the 2023 National Electrical Code at the start of 2026, while unincorporated Maricopa County works to the 2018 International Fuel Gas Code and the 2017 NEC adopted through its Local Additions and Addenda.
Contractor licensing throughout the state runs through the Arizona Registrar of Contractors. If someone proposes gas work without a permit, without a load calculation, or without a pressure test, those are three separate reasons to stop.
If you ever smell gas
- Leave the building immediately, with everyone in it, including pets.
- Do not switch anything on or off. Not a light, not a fan, not an appliance. A switch contact can spark.
- Do not use a phone inside the building. Make the call once you are outside and well away.
- Do not start a vehicle in an attached garage.
- Call the gas utility's emergency line or 911 from a safe distance. That comes before calling a plumber.
- Do not go back in to check, ventilate or investigate. Wait for the utility.
Natural gas and propane are both odorised specifically so that a leak is detectable by smell. That smell is the safety system working exactly as designed, and the correct response is to act on it rather than to investigate it.
The utility has emergency response for this and can shut the supply at the source. Plumbing work follows making the property safe rather than substituting for it, and the repair conversation is useful once you are outside, safe, and the utility is on its way.
Gas supply questions before adding an appliance
Can I just add a tee off the existing line?
Sometimes, but only after a load calculation says the line will carry the additional demand. Teeing in without that check is how the intermittent problems described above get created.
It is also permitted work in most cases, which means sizing, materials and a pressure test all form part of doing it properly.
Why does my tankless unit need a bigger gas line if it uses less gas?
Because sizing is about peak draw, not total consumption. A tankless unit uses less over a day and considerably more while it is actually firing.
A line sized for a storage heater is frequently undersized for tankless. It is the most common surprise in a conversion and it is far better established before the old unit comes out.
How do I know if my meter has capacity?
The meter has a rating, and whether it is adequate depends on the total connected load of everything on the property.
It is the item most often checked last, or not at all. If the pipe is adequate and appliances still falter under combined load, the meter is the next place to look, and upgrading it is a conversation with the gas utility.
Can gas run to a detached building or outdoor kitchen?
Yes, and on parcels this size it is common. The considerations are run length, which affects sizing because pressure drops over distance, and correct materials and depth for the buried section.
Both are worth getting right first time. A buried gas line that has to be dug up and replaced across established landscaping is an expensive way to learn about sizing.
How long do gas lines last?
Interior runs in good conditions last decades. Buried runs vary more, because soil conditions, material and installation quality all affect corrosion.
The useful practice is responding to signs rather than tracking age: smell, hissing, vegetation dying in a line along a known run, or appliances behaving differently than they used to.
Is a yellow flame something to worry about?
Yes, and it deserves the same seriousness as a gas smell even though it is less dramatic. Burners should run crisp and blue; yellow or lazy flames indicate incomplete combustion.
Incomplete combustion produces carbon monoxide, which has no odour, so detection is the only warning. Working carbon monoxide alarms on every level of a building with gas appliances are not optional in a house with a symptom like that.