The Federal Emergency Management Agency (FEMA) cautions homeowners that unanchored fuel tanks can be easily moved by flood waters, posing serious threats to you, your property, public safety and the environment. An unanchored tank outside a home can be driven into the walls of a house by flood waters, or it can be swept downstream, damaging other houses.

When an unanchored tank in a basement is moved by flood waters, the supply line can tear free and the basement can be contaminated by oil. Even a buried tank can be pushed to the surface by the buoyant effect of soil saturated by water.

One way to anchor a fuel tank is to attach it to a large concrete slab that weighs enough to resist the force of flood waters. That method, according to FEMA, can be used for all above-ground tanks. Homeowners can also anchor an outside tank by running straps over it and attaching them to the concrete slab by using turnbuckles.

Propane is stored in pressurized vessels as liquefied petroleum gas (LPG), which can be extremely volatile and potentially explosive if the tank is ruptured and the escaping LPG is ignited by a spark.

An inexpensive way to secure a horizontal outside propane tank is to install four ground anchors connected across the top of the tank with metal straps, according to FEMA. Secure a vertical tank (120-gallon, 420-pound size) with two ground anchors. Set each anchor on opposite sides of vertical tank. Attach a strap from each anchor to the collar secured around top of the tank. Attach another metal strap connected from one anchor to the other through tank base. The ground anchors and straps are the same products that are required by building codes to tie down mobile homes.

The products are available from suppliers and installers that service the manufactured housing industry. Similar products can be used to anchor an outside heating oil tank.

Remember to extend all filling and ventilation tubes above the 100-year flood level so that flood waters cannot enter the tank, and close all connections when flood warnings are issued.

According to FEMA, anchoring a 1,000-gallon fuel tank to a concrete base will cost approximately $300 to $500.