The situation
Illustrative example. Not a real job or customer.
A family in a single-story 1960s slab-on-grade home has a gas tank water heater on a stand in the garage corner, with a metal flue through the roof. The tank is near the end of its life and the family wants to free up floor space and stop running out of hot water when two showers run.
- They fill in a readiness worksheet: the gas line looks small, the range, furnace and dryer are also gas, and there is no outlet near the tank.
- They invite two licensed plumbers for site visits and verify both licenses at cslb.ca.gov.
- Both plumbers measure the gas run from the meter and total the appliance load.
Both conclude the existing gas line cannot supply a tankless unit at full fire alongside the other appliances.
What the two quotes proposed
| Item | Plumber 1 | Plumber 2 |
|---|---|---|
| Gas | New dedicated line from the meter | Upsize part of the existing run |
| Venting | Condensing unit, side-wall vent | Condensing unit, side-wall vent |
| Old flue | Removed and roof patched | Capped at the roof; furnace flue checked separately |
| Electrical | New outlet by an electrician | New outlet by an electrician |
| Valves | Service valves with flush ports | Service valves with flush ports |
| Permit | Included | Included |
How the job went
- Week 1
- Family chooses a plumber after comparing the scopes line by line.
- Week 2
- Permit applied for by the contractor.
- Install day
- Tank drained and removed, gas line installed and pressure tested, unit mounted, vent and condensate drain run, valves fitted.
- End of day
- Unit fired at low and high flow; family shown the shutoffs and inlet filter.
- Later
- Inspection completed; flushing interval written on the family's calendar.
What the example shows
In this made-up case, the unit itself was the simplest decision. The gas line, the vent route and what to do with the old flue were the questions that shaped the job. The furnace sharing the old flue was an easy detail to miss, and one plumber flagged it during the visit.
The family also learned that the conversion did not end on install day. With Fullerton's hard water, the flushing schedule they set afterward is what will decide how well the heat exchanger holds up.
Questions this example raises for your own house
- Does any other appliance share my water heater's flue?
- How long is the gas run from my meter to the heater?
- Where could a side-wall vent exit with proper clearances?
Common questions
Is this a real Fullerton job?
No. It is an invented example written to explain a typical process.
Would every 1960s home need a new gas line?
Not necessarily. It depends on pipe size, length and total load, which a plumber has to check.
Why was an electrician involved?
In this example there was no outlet near the heater, and the gas unit needed power for its controls.
General information for Fullerton, not a quote or professional advice. In an emergency, call 911.