What is a common cause of leaks in UST systems?

Overfilling tanks is a common cause of leaks in UST systems due to the pressure and overflow that occurs when a tank is filled beyond its capacity. When tanks are overfilled, there is a risk that the product can be forced out of the tank through the venting system, leading to potential spillage and environmental contamination. Additionally, the excess liquid can cause stress on fittings, seals, and other components, heightening the risk of leaks.

The other scenarios, while they may contribute to issues in a UST system, are less directly linked to causing leaks. Using only steel materials might lead to corrosion concerns, but without proper maintenance, it does not inherently cause leaks. Insufficient ventilation can cause pressure build-up or vapors, but it does not directly result in liquid leaks. Temperature fluctuations might cause expansion and contraction of the materials, potentially leading to wear and tear, but do not directly correlate to the immediate cause of leaking as overfilling does.