Sump Construction and Size Requirements

A brief Intro about the need for the construction of the sump

Many of the residents living in the urban area heavily depend on the water supplied by BWSSB or what we fondly call as ‘Cauvery’ water supply. But the supply is restricted to twice or thrice in some localities. Some areas get water supply only once in a week. In summer the water supply becomes erratic. So, one needs to find a suitable solution to store the water for drinking and cooking purposes at ground level so that the same can be pumped to the overhead tank. Hence, this is where the importance of sump comes into the picture.

An underground sump forms an important element of the house construction. When one needs to store water, whether its borewell or municipal/ corporation underground sumps come to the rescue as they act as multi-purpose water storage. Water sumps are great alternatives as they ensure continuous water usage in-case if one of the options fails. In fact, before undertaking the construction of a house it is the underground sump that is constructed well in advance so that water can be stored and used during the construction activities.

A careful planning and study is required to construct a sump. As mentioned earlier, it is the sump that gets constructed initially before a house is constructed. This is possible only when the entire plan is well laid out. Sumps can be built as per one's requirements and usage. For instance, in a home if the family members are less, then a sump of smaller size is sufficient. On the other hand, if the members of the family are large then obviously one needs to have a sump with a larger storage area to meet the daily water requirements. This blog article will make things easier for you when you are planning to construct a sump for your home.

One needs to have a sump having a storage capacity of 6000-7000 litres on an average. One can go ahead with a sump having a storage capacity of about 1500 litres that is used for construction purposes initially, and then can expand the storage based on the future requirements. This is to make sure that there is water availability at all times even during scarce times too.

This Article contains

• Essential things to keep in mind while constructing a sump
• Types of materials used for sump construction
• What is a sump pit and how does it work?
• Requirements for sump pits
• What is the need to construct a large sump
• Sump construction procedures
• Underground sump and its merits
• Demerits of an underground sump
• Sump capacity
• Sump and their significance in Bangalore
• Construction of sump and vastu
• Sump construction - FAQ’s
• Conclusion

Essential Things to Keep in Mind While Constructing a Sump

There are certain important points that one needs to keep in mind while constructing an underground sump in a home. One cannot construct a sump as per his/her whims and fancies. One needs to follow certain procedures which are listed below.

SUMP LOCATION

Location plays a very vital part in the home as far as the construction of the sump is concerned. It will be ideal if the location of the sump is at the front portion of the home like an area below the car porch. It is also advisable to have the underground sump close to the main roads where the water lines pass through as it will be easy to give a connection.

SUMP DEPTH

Sumps should have a depth anywhere around 4.5- 5 feet that is considered to be ideal. This is to ensure they can be cleaned easily without any hassles by a person who can keep his head out to avoid suffocation.

SUMP SIZE

The construction of the sump size is calculated based on the capacity. A rough estimate says 1 cubic feet can contain 28 litres of water. So if one needs to have 6000 litres then the size of the sump should be 215 cubic feet.

SUMP WALLS

The walls of the sump should be at a higher level than the ground as this will keep away the rain waters from seeping into the sump.

Types of Materials used for sump construction

A sump can be constructed using the following materials that are listed below.

CONCRETE SUMP

Concrete is the most chosen material for constructing a sump. The material prevents water seepage. The question of water getting contaminated from the ground or sewage does not arise as in the case of concrete sumps. Concrete sumps last for a long time and are easy to clean and maintain.

READYMADE PLASTIC SUMP

These water holding sumps are available in different capacities just similar to overhead water tanks. One major advantage of readymade plastic tanks is that it does not require any plastering work. But, they have a drawback. If the water is left in the tank for a long time, then it can lead to contamination. Moreover, the plastic sumps may not be able to bear the load and cracks may appear in course of time leading to seepage.

BRICKS SUMP

Sumps constructed out of bricks can be a good alternative to plastic tanks, but they have their own limits. The risks are quite high with regard to leakage if not built with proper care. Brick sumps need to have a good quality plastering that is rough on the exteriors and smooth on the interiors. To avoid developing cracks a plastering mesh is recommended.

What is a sump pit and how does it work?

A sump pit is nothing  but a temporary hole built to collect and filter additional water for pumping into the desired designed area. In other terms, it is also known as sump basin. The pit has a vertical standpipe in the centre to catch the filtered water. The standpipe also has a hole. The primary function of the sump pit is to remove the excess amount of water to improve the quality of water. The sump pit also has a sump pump that periodically removes the excess water from the pit. The pits have various water level saving capacities. It also has a water level detector. As the level of water in the pit reaches up to a specific level, the detector activates the pump, and drains the pit water to the desired area.

Requirements for a Sump Pits

Sump Design Criteria

• Sump pits are to be a minimum of 750 mm (30”) deep and 0.25 m2 in area.
• Sump pits are to be fitted with a tightly fitting removable cover.
• Sump pits will be constructed of concrete, plastic, or non-corrosive metal.
• Locate sumps as close to the basement exterior wall as possible (1.2m max) on the side of the building that provides positive drainage.
• Sump pits are to be fitted with an opening to accept a 100mm (4”) drain with the invert of the pipe located above the centre of the sump pits’ height.
• Sump pits are to be placed on even well compacted surfaces.

What is the need to Construct a Large Sump?

There are certain factors that one needs to take into consideration while going ahead to construct a large sump. The size of the family and the frequency of corporation water supply should collectively take a decision for an ideal volume of storage required in order to avoid unwanted expenditure and unhealthy water. A sump with a capacity of 3000 litres and an overhead tank having a capacity of 1500 litres is self-sufficient for most families.

What has sump storage got to do with an eco-friendly approach? Well this question may put many of us in a spot of bother. If you think they are not related, then you are in for a surprise. It is a grey area of concern for most of the home owners who do not think about it as the developers just simply follow a routine practice. Many residents/homeowners spend a large chunk of their money on constructing large sumps fearing water scarcity in a city like Bangalore. This in turn adds more fuel to the fire. Factors like water consumption, cost of construction, stagnation of water, and setback space utilization have an adverse impact on the construction of an underground sump.

As we are aware that stored water does not stay fresh for a long time. As per a recent survey undertaken, residents living in the urban area use approx 150-200 litres of water per person per day. Therefore, a family consisting of five or more members requires approx 750-1000 litres of water every day. This includes tasks like drinking, cooking, cleaning, washing, bathing, gardening, and so on. There are many families who consume water on a sparing basis and avoid all unwanted wastages too. However, to be on the safer side it is better to assume the average consumption for size calculations. 

Sump construction procedures

Now let us understand step-by-step procedures involved in construction of a sump.

• The first and the foremost step are to build an outermost layer with a 4 inch brick wall. This helps the walls of the sump from expanding when filled with water.
• Take excavated mud and fill the outside portions of the wall and soak in water. Take some dhimmis and steel rods to push the mud inside. One can also use concrete to fill up the gaps as this prevents any seepage of water in the building's foundation.
• Allow the wall to sit for a few days and cure it appropriately.
• Now with the help of a barbender build a mat with 8mm or 10mm rods or any remaining rebars with separation of around 4 inches or 5 inches. It is better to consult your structural engineer before proceeding with the work.
• The rebars should be bent onto one another towards the edges and the corners.
• Now tie the mat with the wire mesh as this helps to hold the plastering better. They are secured to the mat using the binding wires.
• Now mix the plaster cement and sand along with waterproofing cement mixtures. This helps make the cement nonporous and block capillary action.
• In the next step, complete the plastering for 1 or 2 inches.
• Instead of a 90 degree angle with each other, do ensure that all corners are rounded while finishing.
• Leave the top of the sump with some protrusions of the rebar mat so that it can join the top of the sump.
• Leave it for curing for at least a week. During this stage, do not fill the tank with water. It is better to cover the sump with any material like tarpaulin or sheets during the monsoons.
• After a week’s time, have another mat built with mesh to do centering. Make sure to leave an opening of 1.5 – 2 feet for a person to get in and clean the sump.
• Now mix jalli stones, sand, and cement in the right proportion to make a concrete mixture.
• Allow it to dry for 10 days once concrete work is done. In the meantime, do not forget to cure it with water.
• Remove the centering once the roof is set. But one needs to plaster the roof interiors by rounding the inside edges of the roof slab.
• The next stage involves finishing the opening part of the sump.
• Now complete the opening by building a wall around the sump up to the desired height. Plaster the interiors and the exteriors of the wall. Place the chamber of the sump on top and plaster for neat finishing.
• Finally, the sump is ready to use. Test the sump by filling it to the full capacity and check if there are any leakages.

Underground Sump and its Merits

• They are more cost-effective than ground storage tanks.
• No water leakage through an open tap as the tap is present in the tank itself.
• The aesthetics of the building is not affected as the sump is located below the ground.
• Best alternative to store rainwater when the groundwater goes dry.

Demerits of an Underground Sump

• Constructing an underground sump is a time consuming process.
• Can cause damage to the main foundation of the building if built very close to the building or the plinth beam.
• Pump is required to take out the water.
• It is power dependent. In case of power failure one cannot draw water.
• To fix cracks and leaks could be a tedious process.
• Since the water cannot be drained out easily, cleaning can be a herculean task.
• If the sumps manhole is left uncovered, it could lead to accidents.
• Poor quality construction may lead to damage of the sump by tree roots.
• Underground sumps may cave in due to the pressure exerted by the earth.

Determining Sump Capacity for Houses in Bengaluru:

Water storage is a crucial aspect of house planning, especially in urban areas like Bengaluru where water supply can be inconsistent. One effective way to ensure a reliable water supply is by installing a sump, which is an underground tank for storing water. The sump capacity needed for a house depends on various factors including the size of the house, the number of occupants, daily water usage, and local water supply conditions. Here we will discuss the recommended sump capacities for houses of 600, 1200, and 1800 square feet in Bengaluru.

Factors Influencing Sump Capacity

• Number of Occupants: Larger houses typically accommodate more people, which increases water usage.
• Daily Water Consumption: The average daily water consumption per person in Bengaluru is estimated to be around 135 litres (as per Indian standards for urban areas).
• Water Supply Schedule: The frequency and reliability of municipal water supply affect the need for storage.
• Rainwater Harvesting: Incorporating rainwater harvesting can reduce the dependency on municipal water supply.

Estimating Water Usage:

To determine the appropriate sump capacity, we first estimate the water usage for different house sizes. Here is a general guideline based on typical household sizes:

600 sq ft house: Generally accommodates 2-3 people.

1200 sq ft house: Generally accommodates 4-6 people.

1800 sq ft house: Generally accommodates 6-8 people.

Using the standard consumption rate of 135 liters per person per day, we can calculate the daily water requirement:

600 sq ft house:

3 people×135 litres/day = 405 litres/day

1200 sq ft house:

5 people × 135 litres/day = 675 litres/day

1800 sq ft house:

7 people × 135 litres/day = 945 litres/day

Calculating Sump Capacity

To ensure an adequate water supply, it is advisable to have storage capacity for at least 3-5 days of water usage. This buffer helps in case of supply interruptions. Below are the calculations for the minimum and maximum recommended sump capacities for each house size:

600 sq ft House:

Minimum capacity (3 days):

405 liters/day x 3 days = 1215 liters

Maximum capacity (5 days):

405 litres/day × 5 days =2025 liters

Therefore, the recommended sump capacity for a 600 sq ft house in Bengaluru is between 1200 and 2000 liters.

1200 sq ft House:

Minimum capacity (3 days):

675 liters/day×3 days=2025 liters

Maximum capacity (5 days):

675 litres/day × 5 days =3375 litres

Thus, the recommended sump capacity for a 1200 sq ft house is between 2000 and 3400 liters.

1800 sq ft House:

Minimum capacity (3 days): 

945 liters/day×3 days=2835 litres

Maximum capacity (5 days):

945 litres/day ×5 days =4725 litres

Hence, the recommended sump capacity for an 1800 sq ft house is between 2800 and 4700 litres.

Practical Considerations

While these calculations provide a good starting point, practical considerations should also influence the final decision:

• Space Availability: The physical space available for the sump construction may limit the size.
• Cost: Larger sumps are more expensive to build and maintain. Balancing cost with need is essential.
• Rainwater Harvesting: If the house is equipped with a rainwater harvesting system, the dependence on the sump can be reduced, potentially lowering the required capacity.
• Future Needs: Consider potential future increases in water usage due to changes in family size or lifestyle.

Sump and their significance in Bangalore

Sumps have become an integral part of every household for many years. Many residents have come and settled in this city over a period of time. Many of the home owners have constructed their own houses and have started dwelling in them. Many of the owners have constructed underground sumps as per their requirements keeping the budget in mind. As many areas in Bangalore do not have regular water supply or the supply is irregular on most occasions, hence the need for sump construction have gone up significantly over the years. Construction of sumps helps to conserve water for present and future uses. Homes with sumps help the residents have continuous water supply even in areas that have scarce supply.

Construction of Sump and Vastu

Vasthu plays a key role in the construction and location of an underground sump. The north-east portion of the plot is considered to be an ideal location for the construction of the sump. This in turn leads to prosperity, increase in wealth, and knowledge of the inmates. An axis needs to be drawn from the north-east corner to the south-west corner while digging the sump. The sump should be dug to the right or to the left side of the axis. The sump located in the east of north-east and north of north-east is most beneficial. Avoid constructing sumps in the south-east, north-west, and in south-west corners of the plot. An underground sump should not be constructed at the centre of the plot at any cost. A vastu homam/pooja has to be performed before the start of the sump construction. Never construct a sump if a woman in the family is pregnant. It is not advisable to construct a sump in front of the main door. The sump should not come in contact with the compound walls or with the main walls.

Conclusion:

Selecting the appropriate sump capacity for a house in Bengaluru is crucial to ensure a reliable water supply. For a 600 sq ft house, a sump capacity of 1200-2000 liters is recommended. For a 1200 sq ft house, the capacity should be between 2000-3400 liters, and for an 1800 sq ft house, between 2800-4700 litres. These recommendations balance the need for adequate water storage with practical constraints such as space and cost.

Implementing rainwater harvesting can further enhance water security and reduce reliance on municipal supply, making it a valuable addition to any household’s water management strategy. By planning carefully and considering all relevant factors, homeowners can ensure that their water storage systems meet their needs effectively and sustainably.

Sump Construction - FAQ’S

Is Sump Necessary?

It all depends on one's needs and requirements. Sumps are one of the best options for filtration but they are not absolutely necessary.

Can sumps be located in front of the main door?

As far as possible avoid constructing a sump in front of the main door. The sump should not come in contact with the compound wall or with the main walls of the house. It should not obstruct the movement of the front gate while opening or closing.

How often should one clean the sump?

Sumps require periodic cleaning from time to time. They need to be cleaned once every 3-4 months. Failure to clean the sump on a regular basis may lead to water contamination.

How do you fix a cracked sump?

Apply the putty over the crack and adjoining areas by working (forcefully kneading) it into place thereby wetting the surface with putty resins. Wipe away the excess putty with a damp cloth.

What is the minimum depth of the sump?

Measure the diameter of your pit and ensure it is larger than 14 inches (18 inches is recommended), so your float switch will not get caught up on the walls of your pit, pump, or piping and risk not activating your pump. Measure the depth of the pit, which should be at a minimum of 22 inches deep.

How to keep the sump water clean?

Use a pressure jet pump to clean the silt, dirt, and algae after first emptying the sump. A potassium permanganate solution is then used to disinfect the sump. Do not ignore cleaning the connecting pipes, foot valves, and floating ball valves.

What is the capacity of an underground sump?

The capacity of underground sump can vary anywhere from 6000 litres to 25000 litres.

Hope this blog article was helpful in providing in-depth information about the various aspects that one needs to take into consideration while constructing an underground sump. If you have any further queries about sump construction, its location, and size then speak to our experts at sqft.expert.