Question 1

How to identify a suitable site for borewell ?

Accepted Answer

To add a Vertical Electrical Sounding is one of the very common geophysical methods used for domestic borewell exploration. However, sufficient open area around the location is needed for conducting the survey. Geologists charge around Rs.1,500 to 5,000/- for identifying a borewell site.Other methods of geophysical survey are used in special cases and they are quite expensive. Local well diviners who use wooden sticks or magnetic blocks are also to some extent successful in identifying borewell sites. But this method may not be always reliable, especially in areas where the geological formation is critical.new question go to app settings and press "Manage Questions" button.

Question 2

How much depth of borewell is ideal?

Accepted Answer

Minimum 200 feets should be driiled for a borewell where borewell yeild is two inches (domestic purpose). For agricultural purpose, it depends upon your the area to be irrigated and water availability in your respective area.

Question 3

What should be the quality of drinking water in borewells?

Accepted Answer

Usually borewells constructed in hard rock areas are free from bacteriological contamination if due precautions like proper installation of casing pipes and avoiding stagnation of water around borewells is taken care off.
If any strong smell or heavy froth forms in the borewell water, it could be due to entry of sewage/contaminated water. Chemical parameters such as iron, fluoride, TDS, arsenic and nitrate are some very important parameters to be normally analysed as they occur in ground water depending upon the geological formations. Other parameters such as pesticides, cadmium, etc., can be assessed on specific cases where such contamination is suspected.

Question 4

Is it safe to drill a borewell very close to the house?

Accepted Answer

A Borewell can be drilled close to a house if the house is built upon normal foundations that are usually recommended for house construction. Shocks waves generated during drilling will be dissipated through soil and rock layers.
However, if you are planning to drill a borewell closer to a massive building which carries heavy loads, it would be better to check for the foundation stability.

Question 5

Can borewells be drilled in locations where ther are space constraints and the rigs can’t reach the site?

Accepted Answer

Portable flexible rigs which function even when their compressor unit is parked at a distance can be used for drilling in such locations. These rigs are only capable of drilling up to a depth of around 300 feet which may be a limitation in sites where deeper borewells are to be drilled.

Question 6

What is the standard diameter of borewells drilled for domestic purposes?

Accepted Answer

What is the standard diameter of borewells drilled for domestic purposes?
For domestic purposes, 4.5 and 6 inches dia borewells are usually drilled. While 4.5 inch is most commonly drilled borewells for domestic purposes, 6 inch borewells are drilled when higher yield is required for large apartments or buildings and also for agricultural purposes.
Initially larger diameter bits are used to place the casing pipes up to the hard rock zone prior to drilling specified size of the borewell.

Question 7

How are charges for drilling a borewell calculated?

Accepted Answer

Charges for drilling a specified size of borewell include
drilling cost per feet,
cost of casing pipe per feet,
cost of drilling and installation charge for casing pipe per feet,
flushing charges per hour for flushing the borewell after drilling and
transportation charges of the rig to the site from nearest town per km.
 Drilling rates are sometimes charged in slabs for specified ranges especially when deep borewells are drilled. As drilling rates usually vary depending on the availability of rigs, local demand and site conditions, it is better to cross check with few drillers to get a competitive quote.

Question 8

What are the types of casing pipes used in borewells?

Accepted Answer

Currently, PVC pipes are very widely used as casing pipe. GI/Mild steel casing pipes which were used earlier are not being recommended due to the problem of corrosion. PVC casing pipes installed in borewells must confirm to IS 12818: 1992 that governs the specification for unplasticized PVC screen and casing pipes for borewell of the Bureau of Indian standard. This standard covers the requirements of ribbed screen, plain screen and plain casing pipes of nominal diameter 40 to 400 mm produced from unplasticized polyvinyl chloride for borewell for water supply.  
Slotted PVC casing pipes are used if aquifer yields through sandy zones to protect collapse of borewell side walls and to prevent entry of fine sand into the borewell which might clog the borewell. This requires detailed study by Geologists to decide slot size and at what depths these have to be provided along with gravel packing around the casing pipe.

Question 9

When and to what depth should the inner casing be laid for a bore well?

Accepted Answer

If there was loose and friable material encountered at the depths mentioned where one struck small quantity of water then one should install the inner casing all the way down to the depth at which water was finally struck. It will prevent the fine sand etc. from entering into the well, filling up the borewell and jamming the pump. If there was no soft or friable material encountered, then there is no need to install this casing.
This Inner casing can be installed at a later date but before the pump is lowered in the borewell. If the material is to collapse and fill up the borewell it will happen when the pump is installed and the borewell is dewatered and water along with fines material starts entering the well from the surrounding area. Actually, a casing with proper screen opening and a gravel pack around this PVC casing should be done.

Question 10

How to determine yield of a borewell while drilling?

Accepted Answer

Usually V-Notches (a metal plate/wooden board with V shaped slot on top) are used by borewell drillers for determining yield of a borewell during the borewell drilling process. To measure the flow, water coming out of the borewell during drilling process is allowed to flow through an earthen barrier created around the site is fixed with a V-notch temporarily.
Drillers won’t be inclined to do so as this is an additional task they have to do. Based on their experience, they tell the rough yield which may not be always correct. Yield of a borewell is usually referred in inches (i.e. depth of water flowing over the notch).

Question 11

Which types of pumps are suitable for borewells?

Accepted Answer

Jet, compressor and submersible pumps are the widely used pumps for domestic purposes in India. Jet pumps which are installed above the ground level over or near the borewell are suitable for depths upto 150 feet. If the ground water is at lower depths submersible or compressor pumps are used.
Compressor pumps are suitable for low yielding borewells and also they are easy to install and maintain as they are installed at ground level. However, they are noisy and may also require frequent repairs.
As submersible pumps of 4” dia which can work in single phase electricity connection are available in the market now, these have become a preferred choice for domestic borewells. They can be installed for meeting higher water requirements. However, submersible pumps will be prone to frequent repairs if they are installed in the borewells containing heavy silt particles.

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