An underground propane tank is an ASME tank built and coated for burial, with only a small dome showing, while an above ground tank sits on a pad or blocks. Burial keeps the yard clear and gives a steadier supply in cold weather, but it costs more to install and needs cathodic protection that must be tested on a schedule. Above ground tanks are simpler to install, inspect, move and replace.
The short answer
An underground propane tank and an above ground tank hold the same fuel and, size for size, deliver the same amount of it. The difference is everything around the tank: how it is built, how it is installed, what it costs to put in, and what the owner has to keep up afterwards. Bury a tank and you get a clear yard and a steadier supply in cold weather; in return you take on excavation, corrosion protection and a testing schedule. Keep it above ground and installation is simpler, the shell is easy to inspect, and moving or replacing it later is far less work.
What makes a tank an underground tank
You cannot bury just any tank. Underground service is a design choice made at the factory:
- It must be an ASME tank. NFPA 58, the national LP-Gas Code, says cylinders (the portable DOT type, such as grill and 100 lb cylinders) may be installed only above ground and must not touch the soil. See our guide to ASME vs DOT propane tanks for how to tell them apart.
- It must be marked for underground service. Stationary ASME tanks are marked for aboveground service, underground service, or both. Some manufacturers build dual-purpose "AG/UG" tanks that can go either way.
- It needs a burial-grade coating and cathodic protection. NFPA 58 requires underground ASME tanks to be coated for that service and to include provisions for cathodic protection. In practice that usually means an anode bag, a magnesium or zinc rod in a cloth bag that is wired to the tank and corrodes in place of the steel.
- Only the dome shows. The valves, gauge and fill connection sit inside a dome or housing with a cover, so the delivery driver fills the tank through a lid in the lawn.
Browse underground propane tanks and above ground propane tanks.
Above ground vs underground at a glance
| Factor | Above ground | Underground |
|---|---|---|
| Appearance | Whole tank visible | Only the dome and lid show |
| Base | Concrete pad or concrete blocks | Excavation, bedding and backfill |
| Corrosion protection | Paint, kept in good condition | Burial coating plus cathodic protection (anode) |
| Ongoing testing | No cathodic protection test schedule | Cathodic protection tests on a set schedule |
| Inspecting the shell | Easy to see rust, dents and damage | Shell is hidden; corrosion can go unseen |
| Minimum distance to buildings and buildable property lines (NFPA 58) | 10 ft for 125 to 500 gallons; 25 ft for 501 to 2,000 gallons, reducible to 10 ft for a single tank of 1,200 gallons or less in some cases | 10 ft from any part of the tank, up to 2,000 gallons |
| Cold-weather supply | Follows air temperature | Steadier, because soil temperature is steadier |
| Flood or high water | May need anchoring | May need anchoring against a high water table |
| Moving or removing it later | Lift and haul | Dig it out, or abandon it in place by the accepted procedure |
Code distances depend on the edition of NFPA 58 your state has adopted and on local amendments, so treat these figures as a starting point and let your licensed installer and local authority confirm them for your lot. Our installation page covers siting and preparation in more detail.
Underground: what you gain and what you take on
What you gain
- A clear yard. Nothing to screen or mow around except a lid.
- Steadier performance in cold weather. PERC's technical guide notes that buried tanks see a more constant temperature year-round, which steadies the rate at which liquid propane turns to vapor.
- Tighter setbacks for larger tanks. A buried 500 to 1,000 gallon tank needs 10 ft from buildings and buildable property lines, where an above ground tank of 501 gallons or more starts from 25 ft.
What you take on
- Excavation and site limits. The burial depth and hole size have to be worked out for the tank and the soil. The tank should sit where the delivery truck will not drive over a septic tank or other buried systems, buildings may not be built over it, and in ground with a high water table it may have to be anchored so it cannot float.
- A testing schedule. For underground tanks installed after January 1, 2011, the LP-Gas Code requires cathodic protection, plus testing and records. North Carolina's LP-Gas regulators describe the usual schedule: a test when the tank is buried, a second test 12 to 18 months later, then intervals of no more than 36 months while results stay acceptable. Results of the last two tests must be kept for inspection.
- Corrosion you cannot see. The same regulators warn that buried tanks can corrode and start leaking over time with no visible signs. The anode and the test readings are how you find out.
- Harder to remove. Taking a buried tank out means digging. A tank can also be abandoned in place by an accepted procedure, but the steel eventually corrodes and the ground above it can settle.
Above ground: what you gain and what you take on
An above ground tank sits on a concrete pad or concrete blocks of a suitable size, so installation is mostly site preparation, setting the tank and running the gas line. You can see the whole shell, so rust, dents and damaged fittings are easy to spot, and keeping the tank painted does a lot to extend its life. If you move house, add on, or want a different size later, the tank can be lifted out and replaced without digging. The trade-offs are that it is visible, it follows outdoor temperatures, and tanks over 500 gallons need more room from buildings and property lines.
Tank price vs installed cost
A tank built for burial usually costs more than the same size above ground, and the hole costs more again. Here are this store's current prices for new tanks at three common sizes, tank only:
| Size | Above ground | Underground |
|---|---|---|
| 250 gallon | 250 Gallon Above Ground Propane Tank: $1,250.00 | 250 Gallon Underground Propane Tank - ASME: $1,700.00 |
| 500 gallon | 500 Gallon Above Ground Propane Tank - ASME: $1,650.00 | 500 Gallon UG Propane Tank - ASME: $3,800.00 |
| 1,000 gallon | 1000 Gallon Above Ground Propane Tank: $3,500.00 | 1000 Gallon Underground Propane Tank (NEW): $4,550.00 |
Installation is a separate cost that depends on your site, soil, permits and how far the gas line has to run. On some tanks you can add installation at checkout, carried out by a licensed installer we arrange locally; each product page shows whether it is available and what it covers. Tanks ship empty by freight; see shipping and delivery. For a fuller breakdown of what goes into the total, see propane tank cost, and for budget options look at used and refurbished tanks, such as the 120 UnderGround Propane Tank ASME.
Ownership matters more when the tank is buried
Whoever owns an underground tank owns its cathodic protection and its test records. North Carolina's regulators note that propane companies handle these requirements for tanks they own, while customers who buy their own tanks are responsible for having the tests done and keeping the documentation. They also note that buried tanks end up owned by the homeowner more often than above ground tanks, though not always. If you would rather not track test dates, leasing from a supplier has real advantages; if you want to choose your supplier and pay for the tank once, owning has advantages too. Our guide on whether to buy or lease a propane tank covers both sides.
How to decide for your property
- Size the load first. Placement does not change how many gallons you need. Start with the propane tank size chart, or our guide to a propane tank for a generator if backup power is the main use.
- Check the ground. Rock, a high water table, a septic field or buried utilities in the only legal spot can rule burial out or raise the cost sharply.
- Check the distances. On a tight lot, the 10 ft underground setback can fit where a 25 ft above ground setback for a 500 to 1,000 gallon tank will not.
- Decide who handles upkeep. Underground means a cathodic protection test schedule for the life of the tank.
- Think ahead. A planned addition, pool or driveway near the tank site should shape where, and how, the tank goes.
Who does the work
Whichever you choose, installing a propane tank is not a homeowner job. Siting, excavation, setting the tank, fitting the regulator and gas line, leak testing and the first fill are for a licensed installer and your licensed propane supplier, working to NFPA 58 and your local code. If you are unsure which placement suits your site, contact us with your tank size and what it will run.
Common questions
Can any propane tank be buried?
No. Only an ASME tank built and marked for underground service, or a dual-purpose aboveground/underground tank, can be buried. It needs a coating suited to burial and provisions for cathodic protection. DOT cylinders, including DOT grill, 100 lb and 420 lb cylinders, may be installed only above ground and must not sit in contact with the soil. Check the tank's nameplate or product listing for its service rating before planning a burial.
How often does an underground propane tank need to be tested?
Underground tanks installed since 2011 need their cathodic protection tested on a schedule: at burial, again 12 to 18 months later, then at intervals of no more than 36 months while readings stay acceptable, as North Carolina's regulators describe it. A failed test means the system must be repaired and the schedule restarts. Keep the results of the last two tests, and ask your supplier or local authority which schedule applies in your state.
How far does an underground propane tank have to be from my house?
Under NFPA 58, no part of an underground ASME tank of up to 2,000 gallons may be closer than 10 feet to a building or to a property line that can be built on. Fill and relief connections also need distance from ignition sources and air intakes. States adopt different code editions and local rules can add requirements, so your licensed installer and local authority confirm the final position.
Can I drive over or build over an underground propane tank?
You should not build over one, and you should not plan to drive over one. NFPA 58 prohibits constructing buildings over underground propane tanks, and PERC's technical guide advises keeping propane tanks away from vehicle traffic and siting buried tanks so the delivery truck does not cross a septic tank or other buried systems. If a driveway or parking area is planned, tell your installer before the tank location is chosen.
Does an underground propane tank work better in winter?
It can hold up better in cold weather. Soil temperature changes less than air temperature, so a buried tank sees a steadier temperature year-round, which PERC says stabilizes the rate at which the propane vaporizes. Above ground tanks lose vapor output as the air gets colder and the liquid level drops. Correct sizing for your load and climate still matters more than placement.
What happens to an underground propane tank when it is no longer needed?
It is either dug out or abandoned in place following an accepted procedure. If a propane company owns it, contact them, since nobody else should remove it. North Carolina's regulators note that a tank left in the ground eventually corrodes and the surface above it may settle, so removal is often the better long-term choice. A licensed professional should empty and disconnect the tank either way.