In frequent scenarios, lift stations are subjected to varying peaks of inflowing water and wastewater. There are different reasons for why these varying flow rates occur, but one simple and widespread solution is the overflow tank. Romtec Utilities works with customers to find the best approach for their packaged lift station project to select and purchase an appropriate overflow tank.
Overflow tanks are relatively simple components. Some engineers will simply refer to them as storage tanks, and from a design point of view, that is pretty much the only function. If the wet well is overcome because of a major event or a component breakdown, the overflow tank will begin to fill. This storage provides lift station operators with time to diagnose and correct any problems before a real overflow occurs.
Typically, Romtec Utilities will propose a design with a secondary concrete vault if the overflow tank does not have a large storage requirement. The concrete vaults are more economical for smaller overflow tanks because it is a less expensive material and weight is not a drastic factor.
Romtec Utilities will propose a design with a secondary vault made of fiberglass when there are larger storage requirements, as shown above . The fiberglass tanks are lighter and easier to install, lowering the price compared to concrete as the tank size increases.
With both types of structural sump materials, it will always be more economical and cost feasible to install an overflow tank as opposed to increasing the volume of the wet well. There are several reasons that this is the case. Primarily, a lift station should be designed to meet a specific condition. Unusual conditions, such a surge in the flow, should not implicate the design of the primary systems. This best practice reduces maintenance issues and lengthens the life-cycle of a station.
Another reason that overflow tanks are more economical than increasing the sump size is that as the sump increases in volume it becomes more expensive to fabricate. So, two small and shallow sumps (a wet well and an overflow tank) are actually more affordable than one really large sump. The other aspect of this is that really large sumps must use larger pumps, which are also more expensive.
With this knowledge, it is easy to understand why the addition of overflow tanks is such a common practice when there are concerns about varying peak inflows. Contact Romtec Utilities today to discuss your project or to get more information on our package lift stations. To get pricing information, visit our simple request a quote form to get an estimate on your project.