The service call: the water-heater swap. Episode seventy-one of the Gas Service Animated series.

A forty-gallon atmospheric water heater, twelve years old, weeping from the tank. The customer wants 'the same thing, today.' Simple job — and simple is exactly where corners get cut. A swap is five systems: gas, vent, air, water, and proof. Walk them all, every time.

Before wrenches: survey what you're inheriting. Gas line: half-inch to the heater off a three-quarter trunk — check. Vent: the heater shares a masonry chimney with an eighty-percent furnace — flag that, it matters later. Combustion air: utility-room door has louvers — check their free area. And the drip leg, the shutoff, the connector all get eyes.

Gas off at the appliance valve, line disconnected, old heater drained and out. New forty-gallon in place — same input, forty thousand. Because input is unchanged, the half-inch branch stands per the sizing table — but you still check the whole picture, because 'same Btu' is a claim, and the nameplate is the fact.

Reconnect like the code reads: new listed connector — the old one never gets reused — drip leg upright, joint compound on male threads only, connector arrows with the flow if it carries a device. Gas on, and every joint you touched gets the bubble test at operating pressure. Tight. That's the leak-check rule after any interruption, in miniature.

Now the flag you planted: the vent. Same-size heater back on the same chimney with the same furnace — the common-vent tables still have to bless it, and this is where orphan logic lives: had this furnace been condensing and gone, this heater alone on that big cold masonry flue would be the classic orphaned water heater — undersized draft, condensation, spillage. Today the pair still works per the table. Check it anyway, every swap.

Combustion air: the louvered door's free area still covers both appliances' input — confirmed against the standard-method numbers. Then startup by the book: purge at the pilot, light per the label, thermostat set, and the draft check — flame at the hood after five minutes of main burner with the room at worst case, doors shut, fans on. It draws.

The water side gets its due: temperature-and-pressure relief piped down, full-size, unthreaded end, air gap at the pan. Set the dial modest, brief the customer on scald and vacation settings. The gas tech who ignores the T-and-P is signing someone else's incident report.

Proof and paper: clocked input matches the nameplate. Draft proven. Joints tested. Combustion air verified. Old unit hauled, permit noted where required, and the customer shown the shutoff, the pilot label, and the relief. A swap done like this is boring — which is the highest compliment in gas work.

The swap in one breath. Survey what you inherit — especially a shared chimney. Same input isn't assumed, it's read. New connector, tested joints, tables re-checked, air confirmed, five-minute draft proven, T-and-P respected, paper done. 'Simple' means all of it, every time. Next call: the new-install walkthrough.