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Tuesday, July 28, 2015

BUILDING THE SUMP

As part of your House Construction, two water tanks are to be constructed: the Underground Water tank and the Overhead water tank. Of these two, the Underground tank also known as the Sump to which the municipal water pipe is connected, is the first to be constructed and should be built before digging for the foundation. This is because, being an underground tank, the excavation must be done before the rest of the foundation-excavation is started.  
So the next step after constructing the temporary shed and organising a watchman to stay in the shed (either by you or by your contractor) is to build the SUMP. Here are some simple guidelines in planning, locating and constructing the sump.

LOCATION OF THE SUMP:

Close to the road: The Sump location should ideally be close to the road as the water lines run along the road. This way, a short connection to the sump from the water lines is sufficient and getting the right slope in the connection pipe is not a matter of concern. Being close to the road is also advantageous when you hire a water tanker to fill up your sump as it is easily accessible.
Under the porch:  Usually the Sump is planned below the car porch because there is ample space available here and it is usually near the road (read water lines). 
Vastu dictates the location of the Sump for some:  Some people prefer to locate it according to Vastu Shastra guidelines. This sometimes becomes a problem especially if they locate it in the back of the site in a tiny space between the house foundation and the compound wall, just because according to Vastu, that is the best position. 

VASTU GUIDELINES FOR LOCATION OF SUMP:

The Sump should be located in the North-East corner.
The Sump should not touch the compound walls or the building walls.
The Sump should be near the corporation water lines, which means, that it should be near the main road.

DECIDING THE CAPACITY OF THE SUMP:

Sump capacity: At the planning stage, you should decide the sump size. This size is directly proportional to the number of famillies/houses that you propose to have in the site and also depends on the water availability. If there is only one house then a 6000 litres to 8000 litres capacity sump is sufficient. If you are proposing more houses for the purpose of giving for rent, then consider an additional 4000-5000 litres per each extra house. A bigger sump is more expensive and takes up space but it is very useful especially when there is water scarcity.

DECIDING THE SUMP SIZE:

Sump depth is usually taken to be 5' and not more as a man (cleaning the sump) should be able to stand in the sump with his head sticking out so that he does not feel suffocated.  

The sump size is calculated based on the sump capacity that you plan to have. As a rough guide, you should consider that 1 cubic feet of space can contain approximately 28 litres of water. So divide the proposed sump capacity with 28 to get the required sump volume in cubic feet, that you have to build.
 The Sump length and breadth area: is calculated by dividing the sump volume by the depth, 5'. The figure that you get will dictate the length and breadth of the sump and the shape of the sump (rectangular or square).

For example: If you decide to have a sump of 6000 litres capacity, divide it by 28 to get 215 cubic feet. This is the desirable sump capacity. Then divide this figure by 5' depth to get 43 square feet. This is the desired sump area. Now you can decide the length and breadth of the sump according to the space available. It could be a rectangular sump of dimensions 4'X11' or 5'X8.5' or squarish with dimensions of 6.5'X6.5' etc.

CONSTRUCTION MATERIAL FOR THE SUMP:

Concrete is the preferred material: Ideally a concrete sump, cast at site is the best for an underground tank. This is because you need not worry about  water seepage and contamination of the stored water from the soil or underground water or sewage. This type of tank will last long and is fairly maintenance-free.

Bricks/blocks can also be used for building sumps: But this type of sump is at risk of leaking if not constructed properly. Use good quality bricks and rough plaster the outside and smooth plaster the inside of the sump. Make sure that a plastering  mesh is used during plastering to avoid cracks. The  sump plastering should be completed at one stretch to avoid cracks.

Ready made plastic tanks (sintex etc) are also avilable in different capacities. They have the advantage that they can be placed in the excavated hole in the site, in a day and there is no plastering or curing required. But I am not convinced about the long term use of water stored in plastic tanks. Moreover I am not sure if they can withstand the pressure of a car above them, if they are placed under the car porch.

Constructing the sump: Water pressure will be more on the internal corners of the tank. So avoid constructing sump/tank corners with 90 degrees like room walls. Instead, have rounded corners so that the water pressure is distributed over a larger area and also so that the corners are easier to clean and do not accumulate dirt.
After the sump has been constructed the next step is to Build the foundation . The steps to be followed in this important aspect of House Construction have been explained in detail here: