Short answer: the sand inside the bag.
It's true; sand-filled sandbags can stop flooding and water.
What allows sandbags to stop flooding and water is the sand contained inside the sandbag.
The sand is fine enough that it can stop individual water molecules from going through.
The bag itself does not stop water.
However, it is important to note that the polypropylene, the type of plastic material used to make the sandbag, is not what stops water.
When sandbags are filled with a coarser material such as gravel, gravel-filled sandbags do not stop flooding or water.
Filling bags with gravel is great for preventing sediment from entering storm drains while allowing water to pass through.
Our customers have found that the water permeability of the plastic allows water that gets in the sand to be released from the bag, so the sand doesn't stay soggy.
Choose a sandbag size to learn more
Be sure to fill either one of these sizes of sandbags with sand to protect your property from flooding.
14" x 26" (most popular)
18" x 30"