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Pump Selection for Borewell: Bannerghatta, Bangalore


For my proposed house construction in 30x40 site, following borewell was drilled.

Borewell location : Bannerghatta, Bangalore South
Drilling time: mid February, 2011

Backyard clearance: North-east corner,
6 feet from north side,
10 feet from east side
Depth of borewell : 356 feet
Depth of 6.5 ” casing : 24 feet
Depth of 10" PVC Casing pipe: 20 feet.

Yield data :

I yield: 55 feet, 1.5", silt, boulders found
II yield: 180 feet, 0.25", silt, boulders found
III yield: 292 feet, 0.25", loose soil

Filter pipe depth : 354 feet (PVC pipe with holes)
Driller Recommended motor: air compressor

It is meant to be used during the house construction, and then to supplement the Kaveri water (municipal supply) for a smally family of four members.

While drilling, the driller said he got rock very early, I think at around 20 feet. After completing the drilling, he strongly advised to go for filter pipes for the full length of the borewell because of silt and boulders. This filter pipe turned out to be PVC pipes with perforations in its entire length.

Right now the borewell is capped. As I am now starting the construction, can you please advise what
type of pump should I go for ?


regards

Sholla

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Comments

1. Pump Selection for Borewell

Dear Sholla,

You have not really mentioned the total yield that you had at the end of the drilling, nor have you mentioned the delivery head that you want to use above ground level. Well with what you have written it suggests that the final yield at the end of the drilling operation was 2 inches. which is equivalent to nearly 3300lph, of which nearly 2200 had been struck by 180ft,

as the water requirement is not really very high, and the yield of the borewell is sufficient, you could instal a 1 hp 12stage pump, this pump could be lowered only down to 200ft,

Or if you want to use the water from the lower most aquifer ( provided it is not in hydraulic continuity with the upper ones) you could install a 1 hp 14 stage pump this has a working head of nearly 90 meters,

This should be sufficient to meet your daily water requirements for construction and also for domestic purpose that you have mentioned.

Naturally, this would be true only if the water yield of the borewell is what you have mentioned.

If your area is known for borewells with siltation problems then it will be ideal to go for an air compressor pump, as there will be no costly movable parts installed inside the borewell, but it is a very inefficient system for pumping.

All the best.

With Kind Regards

Dr. Anil Lalwani

www.wellwaterworks.com

 

2. Dear Member, It is always

Dear Member,


It is always better to maintain the pumping water level above the top of the best, if not the first one, yielding zone. That means the pumping water level should not go deeper than 54 feet below ground level in this particular case. One does not know how far the yield information given by the driller is reliable.
Hence it is advisable to go for a well performance test. You may approach pump dealer and AFPRO or CGWB or Karnataka State Ground water department for appropriate advice.


With best wishes and regards,


Udaya Shankar
Geologists
cudayashankar@yahoo.com

3. Pump Selection for Borewell: Bannerghatta, Bangalore

Dear Sir,

The data informed by you about the ground water flow strata discharge zone as

I yield: 55 feet, 1.5", silt, boulders found 
II yield: 180 feet, 0.25", silt, boulders found 

III yield: 292 feet, 0.25", loose soil

If this is correct during the month of February then the first zone of can be ignered for your effrective pump selections as the period of drilling is just after just 2 month perid at the end of North East Monsoon Season.  What is the peak water level in peak swummer in your area.  Is this 55 feet zone is sustainable.  There has to be a caution.  Is this zone a sustainable one during peak summer of pre monsoon or durinf drought years. 

However since for it is only going to be used for construction purpose, any pump design is not going to affect much.

It is better is assume minimum contribution from this zone and take full contribution from the other zone.  If we do so then the effective yield for design purpose may be about three forth or the maximum of one inch supply.  

This may probebly the reson for the driller to suggest to apt for compressor pump.  How for the quarter inch of addition zone reported is measurable unless the owner is satisfied by his own visual observation during drilling.   

Since you have inserted PVC casing through out, the siltation is minimum.  The information on the pebles provided that actualy filters the silt entry along with the groundwater into the bore well is not clear.  


It is advisable to apt for one H.P. pump that can be installed at about 170 to 180 feet would be more sufficient for you. Since the water level may not fall below 180 feet if you restric you pumping water to a maximum of about 2000 liters at a continues strech of single pumping.  Any 40 LPM discharge 1 H.P. pump or 1.5 H.P. pump would deliver this water in about 50 minutes or with in an hour may be due to fall in pumping water leve.

For construction purpose this may suffice your need per day.  

If the contributing from the main yielding sone stops during peak summer of pre monsoon period, where the ground water withdrawal is at the peak by the society the this design is not an optimum one you have fallow the one that is suggested by Dr. Anil Lalwani.

With warm regards,

A. Raja Mohamed

Geophysicist

bismi1234786@gmail.com 9443619352

A. RAJAMOHAMED AMBALAM GEOPHYSICIST COASTAL ENERGY Pvt Ltd, CHENNAI +919443619352

4. Re: Pump Selection for Borewell: Bannerghatta, Bangalore

Dear All,

Thanks you for your kind responses. I can now report some progress in this regard.

I contacted a pump dealer who had done an installation near my site and
based on his recommendation installed a 2-HP submersible at a depth of 250 feet.
Based on his measurement, there is still about 90 feet below this point.
Dealer also had put two layers of white fine mesh around the submersible inlet.

Our initial run shows that the pump runs for about 15 minutes, initially high
pressure and gradually decreasing. Water has no smell and clear.

How can I test whether there is any silt coming along with this water ?
Also, should we lower the pump still further down ?

My worry is that now in rainy season if this is all the output, surely in
summer it will be very bad.

Any suggestions to improve this sitation ?

Regards
sholla

5. Pump Selection for Borewell: Bannerghatta, Bangalore

Dear Sir,

As guessed by me what all you get during your trial pumping of the recent effect is that you are getting presently the supply from the shallow zone near 55 feet that is contributing mainly for your pumping of 2.5 h.p motor. that is installed at about 250 feet.

While seeking some sugggestion or advice kindly try to submit maximum information as possible.  Now how muxh amount of water you had pumped in this 15 minutes.  We have to max a mental calculation or gues and give you some suggesions.  Your 2.5 h.p pump have discharged.  Before starting your pumo what is your water level from the ground where it standing at 50 feet or 60 feet or 35 feet or 3o feet. 

Assuming about forty feet level, about a 15 feet rise due to hydrostatic pressure, you have pumped about 1300 to 1400 litres from the storage and the remaining from the instentaneous recharge from your aquifer.

May be the 2.5 h.p pump at a depth of 250 feet would have  discharged it looks to have pumped out your stored water only because the the discharge rate calsulation indicates a rate of about 86 L
itres per minutes.  To my calcluation the 2.5 h.p pump may not dicharge more that 100 LPM at 250 feet head.  With out a pump discharge rate further advise or comments can not tbe narrated.

This implies that your 55 feet isw contributing very very megare amount of discharge into the bore well.  During peak summer the discharge may even still less.

to get more water from storage you can install at deeper depth. every one meter of your borewell may store about 20 litres of water.

To increase the yield you may attempt hydrofracturing at 180 feet and 22 feet zones where fractures are indicated.

To check the siltaion conduct turbidity test. This may not be reqauired as you are getting siltless water. As you have inserted filtered casing throughout,  You can use a fine  to very finely nitted cloth and filter the oumped water and sheck for any silt.  If you want to go for scientific analysis please do the turbitity test.     

With best wishes,

A. Rajamohamed Ambalam.

Geophysicist.

bismi1234786@gmail.com

9443619352

A. RAJAMOHAMED AMBALAM GEOPHYSICIST COASTAL ENERGY Pvt Ltd, CHENNAI +919443619352

6. Pump Selection for Borewell: Bannerghatta, Bangalore

Dear Sir,

Thank you for your response. Sorry my previous response did not have the measurements. Right now construction is going on and I am finding it very difficult to measure the water depth and the volume of water pumped out.

You mentioned pump discharge rate , I guess I have to contact the dealer for this.

I am in the process of constructing a sump. Once it is done, I will once again observe the parameters  and report back.

Regards

Sathish

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