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Pump Selection: Expert Advice Required! - Ghaziabad, Uttar Pradesh

This is to solicit an opinion from those who have some knowledge of pumps, etc.

There are 2 submersible pumps that send groundwater to the overhead tank. One is 5kvA, the other is 7.5 kvA. One of these, the 7.5kvA one has been crippled over the last 2 months or so. Despite having given it to an authorized servicing agency, we have not been able to commission it so far. The motor winding of the pump is burning out again and again. We have replaced the motor control panel meters, and the wire that supplies power to the pump underground. Still, no use.

 The pump has seen 9 years, and is probably at the end of its life. So some residents opined that we should buy a new one instead of repairing it. We contacted a major distributor of  pumps, which is a leading brand of submersible pumps in the country. Both our existing pumps are KSB make. The person at the other end asked us the depth of the borewell and the height of the water table. We did our own measurement and the borewell came to be 107ft. deep, and the water starts at about 50ft. from the ground, approximately halfway.

 The pump engineer told us that the amount of water is too less for the power of a 7.5kvA pump. If used, it may burn out or may suck the floor dirt from the bed of the borewell. Coincidentally, our motor is indeed burning out repeatedly, and it has sucked considerable dirt, damaging the blades inside. So, what the engineer told us matches our experience.

All this leads us to the conclusion that the water table has gone down over the last 9 years. If so, I have doubts we will last another decade if we do not do anything fast. Anyway, that is a separate thread to discuss. Ideas there are rainwater harvesting, conservation of water, etc.  The engineer is asking us to buy a less powerful pump, but we know that the 5kvA pump struggles the entire day, non-stop, to get water into the overhead tank. If Ganga water was not there, we will not have 24 hrs. supply today.

Kindly advice us regarding how to proceed regarding the issue.

 Warm Regards

Sanjay Chakravarty

Vice-President,

Ashiana heritage Residents Welfare Association ( AHRWA)

Ashiana's Heritage, Plot 14, Sector 4, Vaishali, Dist. Ghaziabad, U.P.

sanjaychak01@gmail.com

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Comments

1.

Your problem does not lie in the pump or the motor,it is actually the yield of the borewell as indicated by the company engineer's.By knowing the total depth of the borewell and the static water level alone will not solve the problem.A yield test has to be conducted before installing or selecting the pumpset.
It does not mean always that the pump should work non stop to suppy the required quantity of water per day, it can be made to run in a cyclic manner to pump the required quantity of water depending on the yield of the well.

If it was in bangalore i would have personally visited to your site to brief you about the problem and the solution for it (We are a bangalore based water well rejuvenating company).

I can definitely help you by letting you know the procedure to conduct a simple recuperation test to determine the yield of the well so that you can select the right pump and also understand the cycles of pumping.

You can email me on my mail id for further details.

karu_bangalore@sify.com

2.

Dear Sanjay Chakravarty,

I have noted that the contents of your query and it might be concluded that as pointed out by others that your 7.5 H.P pump is sucking out all the water. When there is no water and still if the pump runs then may be after a couple of minutes, the coil will burn out.

If you would have provided the details of the residents’ strength, we can estimate the total water required and design the system and inform it to you. Never the less, from the way you have narrated, the 5 h.p is running round the clock and still it is insufficient, your need is close to 7.5 or 10. H.p pumpage requirement. Even if you do some RWH measures, it may not suffice the current need.

It is advisable to drill a new bore by the side of your old bore to a depth of about 180 to 200 feet. As it is situated in the alluvial recent formation, there is possibility of getting sand horizon up to 300 feet. Please look around your neighbouring areas and find out the maximum depth of the bore well / tube well drilled / constructed with in the radius of 500 meter and accordingly drill your bore well also to that depth. The best would be to consult a Hydrogeologist and go by their opinion.

Availability of ground water in your terrain is not at all a problem but the quality for potability and suitability has to be assessed and it should be focused by you or by the consultant while deciding the depth of the bore well. Kindly do the necessary quality test before commissioning.

Please install suitable pump may be 7.5 or 10 h.p to lift water to your over head tank.

With best wishes,

A. Rajamohamed Ambalam
Geophysicist
Coastal Energy Private Limited
Chennai - 600006

3.

Sanjay Chakravarty,

I do believe you when you say that you have got your motor repaired a couple of times and it is repeatedly getting burnt.

The reason for the burnout may not necessarily be due dry run,

1) Pump is normally never installed at touching the base of the borewell there is always some gap between the level the pump is installed and the base of the borewell (standard Installation Procedure)

2) It is possible the stamping of the rotor has developed a problem; usually one never takes this in to consideration.

3) The thrust plate assembly may have gone bad or given way and has not yet been replaced only winding wire is being replaced.

4) The control panel for such pumps usually has a Dry run protection built in as a safety measure; this seems to be missing in your panel.

5) The capacity of the well is not decided by the standing water column within the borewell, but on the aquifer response time, which is dependent on the capacity of the aquifer.

My advice is to first run a test to ascertain the present day specific capacity of the borewell, by recording the specific discharge per meter of drawdown, and then find out the total permissible draw down naturally this is easy to calculate by trying to keep the discharge such that the pump is always submerged in a 3 meter water column.

It may be possible that the discharge of the pump needs to be throttled a bit, but that should really not make much of a difference.

About the rainwater harvesting that is been propagated I doubt that we will be able to meet our fresh water requirements in the near future. The reason for this being that there has been thought been given to the capacity of the aquifer, the quality issues which need to be taken in to account while implementing this kind of measures by wrongly trained personnel.

Hope I have managed to answer you query

Dr Anil Lalwani
http://www.wellwaterworks.com

4.

Errata

please read 80 mtr as 80 feet

50 mtr as 50 feet and

20 mtr as 20 feet

5.

Any running Electric motor needs continuous cooling. Submersible pumps are continuously cooled by upflow of water. Dry running(no cooling) of submersible pump will burn its winding.

I can only guess that your pump is of 40 mtr head and about 15 LPS(litre per second) capacity. So 54000 litre per hour water will be withdrawn continuously from borewell. If your pump is hanged at 80 mtr below ground level and water table appears at 50 mtr, there should be atleast 20 meter head of water above pump if borewell output capacity is good.

If borewell capacity is less than 50000 ltr/hour than there are chances of dry run of motor.

In my opinion you should check borewell capacity by measuring water head depletion in borewell when withdrawing water from it.

regards

Anil Kumar Singla

6. How to select borewell pumps for home

Dear  Sir,

Please advice me on how to select the right pump with starter, cable and pipes for home.

Details are given below

  • Diameter of bore: 6’ 5”
  • Casing pipe Length: 100 meter
  • Water obtain from length: 265 feet
  • Total bore length: 500 feet

7. Selecting pump for borewell

Hi,

Recently we have drilled a borewell in Bangalore. The total depth of the well is 980ft and while drilling water was hit at about 920 ft. The contractor told that the yield was 3 inch (I do not know what that means).The well is mainly for household purposes. Can anyone please advice me on the type and cost of pump to be used for the same.

Specifications of Bore well: The steel casing pipe used for the borewell is 6.5 inch (diameter) to a depth of 60ft after which we hit rock and did not use any pipe.

My requirement is to fill a tank of about 1500 to 2000 liters in maybe 30 to 45 minutes. Also we are planning on single phase electric connection only.

8. Selecting pump for 925ft borewell-East Bangalore

Hi experts,

We have drilled a borewell in East Bangalore (Mahadevapura). The total depth of the borewell is 925ft and I got water around 840ft. We have installed MS casing 6.5" till 73 feet depth, after that rock. Yield is 2".

My requirement is to get water for two houses.

Please suggest the pump which can suit the needs.

Thanks,
Pradeep

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