A water storage tank collects water and stores it for later use- as and when required. Residential water tanks are required to store water for many purposes like drinking, harvesting, gardening, fire safety, household usages, irrigation etc.   There are many kinds of water storage and supply systems. The most common ones are the elevated water tanks (overhead water tank), ground tank and underground water tank. They differ in their placements, supply systems and the materials they are made up of. The materials that depends on the locality, weather, size and their usage. 

Apart from the differences in their sizes and materials, they can also differ on the basis of the way they supply water for the household use. There are majorly two types:

1.Pressure tank

A compressed air is used to create pressure in the water stored into it. It is constructed with an air chamber with a pre-existing pressure. So now, when the water gets filled, due to the weight of the water the pressure increases. When one requires water in the house, like when the flush is pressed and the outlet opens, the water gets supplied due to the pressure.

2.Atmospheric Tank

In such a setup, there is no pre-acquired pressure in the water. But the water rests at the atmospheric pressure. An additional pumping system needs to be installed to supply water to their required spots. 

So, this was a brief about water storage and supply systems for clean water. But what about the water that needs to be collected from the rain and storm? Water being an inevitable resource needs judicious systems as well. There are many uses of stored rainwater and stormwater and that is exactly why their harvesting systems need to be installed in a household.

• Flushing toilets
• Washing cars, driveway, clothes
• Irrigation for garden
• Outdoor ponds/ water feature
• Composting
• Fire Protection

For such vivid usages of rain and storm water, there are special systems developed for their storage and supply. Plus, it definitely brings down the water bills. Rainwater is generally collected directly from the roof tops and is harvested in these tanks. It is free of large debris and unwanted wastes as the water was collected before coming in contact with the ground. On the other hand, storm water passes from the roof gutters and downpipes and/or surface runoffs and gets collected. Hence, it contains more debris than the rainwater.

The main component of these systems are Water Retention Tank and Water Detention Tank. So, what are these tanks for and how do they work?

1.Water Retention Tank

It is designed to harvest rainwater/ storm water on your property and thus it retains water for further uses with lesser risks like flushing, gardening, composting, washing etc. It can even be used for drinking purposes if the collection system is maintained and one wants to avoid drinking water from the supply with chemicals. It is even beneficial in rural areas where there is a lack of reticulated water supply.

2.Water Detention Tank

These tanks temporarily store water and then slowly allow the water to discharge back into the water table or into the public water systems. The water from the rooftop and the surface runoff gets collected into the tank. The system is such that it prevents large debris into the tank. The water is then slowly discharged through a smaller outlet. 

Now how is this helpful? Heavy rainfalls and storms the sewers exceed the intended flow capacity. Untreated storm water carries unwanted debris and pollutants and through a surface runoff they get deposited in lakes or rivers. Settlements might increase per square mileage but many of the gray infrastructure systems are not upgraded at the same rate. To help the situation some local authorities have made it mandatory to have these systems installed in households. 

Thus, a slow release of water into the sources or drains helps assist the local authorities with water runoffs, helping to prevent flooding. 

Design Considerations

• They can be installed above ground on buildings, underground or above the ground.
• Location will assign its operation and effectiveness. The water that gets discharged with gravity will require lesser operational costs.
• Developers may assign various detention systems. Selection of these systems depend on space availability, site topography, operations and maintenance. Large sites have greater flexibility of implementing one or more such systems.
• There is also a dependence on internal and external drain levels.
• The discharge outlet should be designed keeping in mind the downstream water level in drain to enable free discharge and prevent backflow.
• It is also advisable to construct an overflow structure into the system in case the system malfunctions.
• Adequate measures must be put in place to also prevent mosquito breeding.