Structural composite retention tanks are designed For durability, dependability and resistance to corrosion. They're also constructed to provide optimal contact time For chemical treatment applications. Because they are lightweight, these seamless retention tanks are easily installed, making them ideal For both new installations, and as replacement tanks. In residential applications, contact tanks are often used in order to store water post chlorine treatment. The storage of the water and chlorine in the contact tank allows For adequate reaction time before particulate filtration and use.