Plumbing SOP Example

Tank Water Heater Replacement — 50 Gallon Gas

Gas water heater swap in utility room with new flex connectors, proper venting, and 120°F setpoint.

1. Shut down & drain existing unitTurn off gas supply at the unit shut-off valve — confirm with combustible gas detector. Set thermostat dial to PILOT or OFF to allow burner to cool. Close cold water inlet valve. Connect a garden hose to the tank drain valve at the base and route to a floor drain, utility sink, or exterior. Open a hot-side faucet in the building to break the vacuum and allow the tank to drain. Expect 45–60 minutes to drain a 50-gallon tank fully.
2. Disconnect & remove old unitWith tank drained, disconnect gas line at the union — immediately cap the building stub with an approved gas cap. Disconnect flue vent — inspect vent pipe for corrosion and set aside if reusing. If water connections are soldered copper, cut pipe 2" from tank nipple using pipe cutter and deburr cuts. If threaded, use pipe wrench at union. Dolly old unit out for haul-off. Inspect gas line sizing, shut-off valve operation, and vent condition before installing new unit.
3. Position new unit & make water connectionsPosition new 50-gallon heater in same location — ensure unit is plumb and level (check with level on both axes). Install new dielectric unions on both hot and cold nipples — these prevent galvanic corrosion between steel and copper connections. Connect new braided stainless flex connectors from dielectric unions to existing copper supply lines. Cold connection goes to cold inlet nipple (marked blue or with arrow indicating direction of flow). Hand-tighten, then snug with channel-lock pliers — 1/4 to 1/2 turn past hand-tight only.
4. Gas connection & vent reconnectionReconnect gas line using new union and approved gas pipe dope (no Teflon tape on gas connections — Teflon can migrate into valve seats). If flex connector is used between rigid line and unit, ensure it is listed for gas use and is not routed through any enclosed space. Reconnect flue vent — ensure male end of vent pipe points in direction of draft (toward unit, not chimney). Verify proper draft slope and that no section has a sag that could trap condensate. Secure all vent connections.
5. Fill tank & leak testOpen cold water inlet valve slowly. Open a hot-side faucet in the building — leave open until water flows steadily with no air or sputtering (typically 5–8 minutes for a 50-gallon tank). Close faucet. Inspect all water connections for drips — check dielectric union, flex connector fittings, and tank nipples. Tighten any dripping connections 1/4 turn at a time. Do not proceed to gas until water connections are confirmed dry.
6. Light & verify operationRestore gas supply at shut-off valve. Relight per manufacturer label instructions — modern units have electronic ignition; older units require manual pilot lighting procedure on label. Set thermostat dial to 120°F (hot water scalding prevention standard). Verify burner ignites and the unit cycles through a full heat cycle. Confirm no gas odor with detector at all connections. Verify draft by holding smoke match or stick near draft hood — smoke should be drawn up into the vent.
7. Documentation & homeowner instructionsPhotograph completed installation showing all connections, gas line, vent, and equipment label/serial number. Record installation date, unit model, and serial number in project file. Explain thermostat location and 120°F setting to homeowner. Review anode rod inspection timeline (every 3–5 years). Leave warranty card and installation documentation with homeowner. Advise homeowner to call immediately if they detect gas odor.