For homeowners who heat with fuel oil, adding a second storage tank can provide significant cost savings. Buying a full winter fuel supply during summer when heating oil prices are lowest is a smart financial strategy.
Why Add a Second Oil Tank?
Heating oil prices fluctuate seasonally. Prices are lowest in summer when demand is minimal and highest in winter during peak heating season.
| Season | Typical Price/Gal | Single Tank (275 Gal) | Dual Tanks (550 Gal) |
|---|---|---|---|
| Summer fill | $2.80 | $700 | $1,400 |
| Winter top-off | $3.50 | $875 | $0 |
| Total annual cost | $1,575 | $1,400 | |
| Annual savings | $175 (11%) |
System Design: Parallel Feed
The simplest and most reliable configuration connects both tanks to a common feed line. Both tanks feed the furnace simultaneously, eliminating the need for manual switching valves or level monitoring.
Components Required
- Second 275-gallon tank on stable level platform
- Steel fill and vent piping with threaded connections
- 3/8-in. soft copper tubing for supply lines
- Full-port ball shutoff valves at each tank
- In-line oil filters for each tank
- Copper tee fitting to join supply lines
Installation Steps
1. Position the Second Tank
Place it in a location allowing access for filling and inspection. A full 275-gallon tank weighs approximately 2,100 pounds. The surface must support this weight.
2. Install Fill and Vent Pipes
Each tank requires its own fill and vent pipe through the exterior wall. Use steel pipe with threaded connections. The vent must terminate at least 12 inches above grade and 2 feet from any window.
3. Connect Supply Lines
Turn off the valve on the existing tank and disconnect the supply line. Install a copper tee fitting. Connect one branch to the existing tank through its valve and filter. Connect the other branch to the new tank. Use flare fittings for all connections.
4. Valve and Filter Configuration
Each tank must have its own shutoff valve and in-line oil filter. Label each valve clearly so either tank can be isolated for maintenance.
Operation: Let Both Tanks Feed Simultaneously
Leave both valves open. Both tanks will drain at approximately the same rate. Do not install automatic switching valves or attempt manual switching. Parallel operation is simpler and more reliable.
Safety Considerations
- Check local codes for permits and specific requirements
- Use only approved oil-rated copper tubing or steel pipe
- Install whistle vents for audible fill indication
- Keep a spill kit accessible
- Inspect tanks and lines annually for leaks
Conclusion
Adding a second oil tank reduces annual heating costs through off-peak fuel purchasing. A properly designed parallel supply system with independent valves and filters for each tank provides automatic, reliable operation.