The numbers you look up on a driveway. Save this page to your home screen.
Cathodic protection, the 15 install stages, clearances, buried-tank rules and what to do with another company’s tank — two pages, made to live in the truck.
| Passing reading | −0.85 volts DC or more negative, against a copper/copper-sulfate half cell. −0.92 passes. −0.78 fails. |
| Typical range | Readings run about −1.80 to 0.00. Anything between −1.80 and −0.85 is protected. |
| Test schedule | At installation · again 12–18 months later · then at least every 36 months. Shorter if the AHJ says so. |
| If it fails | Re-test first (wet the soil, check the cell, check contact) → look for a short to other buried metal → anodes → repair as soon as practical → retest and restart the schedule. |
| Records | Keep at least the last two inspections on file. |
Nameplate always wins. These are for sizing conversations before you have one.
| Appliance | Typical BTU/hr |
|---|---|
| Range / cooktop | 65,000 |
| Tankless water heater | 150,000 – 199,000 |
| Tank water heater (40 gal) | 40,000 |
| Pool heater (400k) | 400,000 |
| Standby generator (22–24 kW) | 250,000 – 300,000 |
| Fire pit / bowl | 65,000 – 150,000 |
| Linear fire feature | 90,000 – 200,000 |
| Outdoor grill (built-in) | 60,000 – 90,000 |
| Clothes dryer | 35,000 |
| Fireplace insert | 40,000 |
| Tank | Usable at 80% | Usually suits |
|---|---|---|
| 120 gal (420 lb) | 96 gal | One or two appliances — cooking, dryer, tankless |
| 250 gal | 200 gal | Small whole-home, pool heater |
| 500 gal | 400 gal | Whole home, generator, pool |
| 1000 gal | 800 gal | Large estate, commercial, multiple heavy loads |
Tanks fill to 80%. A gauge percentage is a percentage of that usable volume — a 500 at 90% holds about 360 gallons.
| Pressure test | Record the test pressure and how long it held. “Held with no drop” is the only pass. |
| Leak check | Every joint and fitting. Anything found gets repaired before you leave or written up as a return visit. |
| Regulator | Record the reading in inches of water column. Vent clear and pointed down. |
| Clearances | Check distances to doors, windows, ignition sources and equipment — and that nothing has grown or been built into the space. |
| Photos | Tank, regulator, anything you found. They attach to the job for the office. |
Leave the area immediately and call 911. Don’t switch anything on or off on the way out. Once clear, call us. Never tell a customer to go back in and check something.
