Underground propane storage tanks are long-lasting and environmentally friendly. With proper protection to resist rust and corrosion, they will generally last for 30 to 40 years. In the unlikely event of a leak, propane will not pollute the soil or groundwater because it is non-toxic.Click to see full answer. Moreover, how often do underground propane tanks need to be tested?In many states, if your tank was installed after January 1, 2011, the system must be tested by a qualified service technician within six months of installation and at least every three years thereafter. You will need to keep the results of the last two tests to document that the cathodic protection is working properly.Furthermore, are buried propane tanks safe? Propane tanks, whether buried underground or located above ground, are inherently safe. In the unlikely event of a release, propane is not harmful to soil or water, plus there are strict controls and codes that govern a tank’s placement. how much do underground propane tanks cost? An underground and buried propane tank costs between $1,125 and $5,150 with most homeowners spending $1,870 for a 500-gallon tank, and $4,400 to install a 1,000-gallon tank in metropolitan areas. Tanks from 250 gallons upward can be installed underground, with 500- to 1,000-gallon tanks being the most common.How long will a 15 lb propane tank last?A disposable 14 or 16 ounce propane tank will last about 1.5 to 2 hours. A standard 20 lb propane tank should last about 18-20 hours on most grills. We always recommend that you have an extra tank on hand because you don’t want to run out in the middle of a bbq!