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Plumbing Worries: Pump Choice?: Detailed Query, Schematic Sketch.

Few months back we purchased a new Openwell Submersible Pump for our Apartment. 2 HP, 1¼ " Suction and 1¼" Delivery for a head of 70 Mts. We have connected the delivery of the new pump to an existing  1" line to pump water to Overhead tank.

After this our power bill has increased two fold.  When I contacted few experts they suggested that the delivery pipe should be equal or greater than the specification mentioned on the pump i.e.  1¼" or 1½".

Can someone please guide us in this matter.

Plumbing Plans, access here: Schematic sketch

Sai Kumar

skmodem@gmail.com

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Comments

1.

Dear Sai Kumar,

What I can say Sai is that only part of the analysis is true. The pump has to give 70m head so I trust it is of about 5 hp or higher depending on the rated discharge. The power consumption is because of higher amperage consumption and the pipe size is only increasing the back pressure. What is the depth of borewell and what is the height of the over head tank. If you can tell me that may be a better solution can be provided.

With best regards,

Taral Kumar
Executive Director
Akar Impex Pvt. Ltd.
Noida, Uttar Pradesh

2.

Dear Sai Kumar,

There will not be any significant load due to slight reduction of pipe dia. High electricity consumption is may be due to make and model of ESP. ESP may have high RPM motor suitable to meet the high dynamic head requirement than your requirement.

You may like to go through its brochure and find out power consumption under different condition.

Dr. Ashok Kumar
Groundwater Consultant (Modelling)
Vikramshila Society for Social and Educational Development
New Delhi

3.

Dear Sai Kumar,

The pump is hugely undersized. A submersible pump may have a total head of only about 60 - 65 meters but then that would be 10 H.P. and a self priming pump can be of 7.5 H.P. but would give a greater discharge and head as compared to the submersible one. These pumps would fill up their OHT in about 3 to 4 hours.
To my opinion the 2 H.P. is giving them the 70 meter head, because the pumping is by 1" line.

The higher diameter pipe would reduce their head and discharge. You must check up with a chart supplied by the manufacturer who gives both characteristics: Flow vs. Head for various pumps. On basis of which only they can make a choice. The pipe line in any case would have to be changed as the larger size pump would require it to be so.

It is better to buy the self priming pump of 7.5 H.P. and their electric bill should be around Rs. 2000-2500 (depending on their local power tariff). This would solve their pumping problem, their cost problem.

Regards

Keshav Agarwal
Technical Consultant
Biotech Services
Noida, UP
http://www.septictanktreatment.biz

4.

Dear Sai Kumar,

In continuation of my earlier reply I have couple of more details to make things clear. The pump has to give 70m head and since it s 1 hp motor, I trust it is of about 2 cum/hr. flow as per the rated discharge. The power consumption is because of higher amperage consumption and this is because of the back pressure of the pumping flow.

The pumped flow is supposedly higher but owing to smaller pipe, the flow is reduced and you have excess amperage consumption since the entire motor torque is consumed to pump the flow. You may replace the pipe and also check the pump rated discharge.

For 45 flats (40 occupied), flow of 1000 liters per flat or 40 cum is ok. The pump shall be of capacity 8-10 cum/hr. That way, it needs to operate only 3 hours in the morning and 2 hours in the evening. That should be carried out by a pump of 3 hp and the pipe size shall be between 40mm-50mm. This way, you shall get a shorter operating duration as well as lower power consumption. And, less running means less wear and tear.

With best regards,

Taral Kumar
Executive Director
Akar Impex Pvt. Ltd.
Noida, Uttar Pradesh

5.

Dear Saikumar,

The apartment arrangement would be to have one pump submersible of just the right capacity to extract water and fill up the sump. You may use a 3hp pump and this can operate on low flow and longer duration, as the well receives water it would pump, at no case the discharge to be more than the water formation in well.

If the well has not been developed recently do the same. The water flow would depend on the ground water levels and hope that has not got receded. Regarding the size of pipe bores 2 to 2.5" would be fine, how much is the bore well casing size?

The practice of filling the sump for around 18 hours, and settling for 6 hours, is a good procedure as all silt and others will get settled down.

Next the water from the sump to be pulled up to the OHT, for this also you can have the same type of pump located in the sump, the inventory of pump-spares etc. will be taken care off. Here also pipe size 2 to 2.5" can be used. The pump operations can be controlled say for 10 hours in 2- spurts. One in the early morning, one in the late afternoon etc.

This gives ample amount of settling time for the turbulence to settle down caused by ground water pump in sump. Also the municipal line water to be received, do you suck this water also to fill up your sump, also is to be taken care off.

If you get more it is good for you, do you have a WTP also, and how good is your municipal water.

Both the above pumping consumption would be 18+10= 28 hrs. 2 units 50 units times Rs.3/- Rs.150/- per day, say Rs.4500/- per month this is on the higher side,,, I am giving you a rough calculation, you are the right judge.

Are you near Delhi, our NGO Supervisor could visit you to sort out the problem.

With wellwishes from VigyanVijay,

Er. Ajit Seshadri
Head-Environmental Wing
The Vigyan Vijay Foundation
New Delhi-110 045

6.

Dear Sai Kumar,

After a careful study of the information provided by you my recommendations are as follows:

1. Pumps: It would have helped if you had given information on the pumps e.g. single phase motor or 3 phases? What is the output flow in litres and discharge head in metres? My guess is that the 2HP pump is capable of a flow of approx 3 to 4 thousand litres/hour. In this case, it will take 6 to 8 hours to fill the over head tank (OHT).

According to your query, it takes 20 hours to fill the OHT which means that the pump is capable of pumping approximately 1000 to 1250 liters/hour. This is due to the pipe line diameter of 1 inch where it should have been 1.25 inches. Changing the line to this bigger size will definitely improve matters.

2. Water consumption in the building: In India, all water supply authorities/municipalities work on a water consumption of 135 litres per capita daily (lpcd).This represents the water consumption per individual per day. If we apply this standard we will get the total expected consumption by the residents of the building by multiplying no. of residents X 135 liters. I have assumed that the number of persons in each of the flats will be

a) 3 BR flats=5 per flat.

b) 2 BR flats=4 per flat and

c)1 BR flat=2 per flat.

Based on this and assuming full occupancy the total population works out to 220 people. Hence water consumption would be 29700 liters/day. Like most buildings I have dealt with this building too has now water meter to measure the water consumed. Guessing on the basis of OHT capacity invariably ends up with an error of + or - 10 to 15% in my experience.

In 95% of the cases I have handled, the building residents were consuming far in excess of the standard figure of 135 lpcd. In this case too water consumption is likely to be excessive. Installing a water meter at the inlet of the OHT (install the meter in horizontal position) will help to monitor the consumption. A reading should be taken at a fixed time on each day and recorded. (I would be interested in knowing the results of this exercise!).

3. Source of Water: As far as possible the residents of the building should use municipal water supply as far as possible and bore well water only in emergencies.

4. Electricity Consumption: Once again, my experience shows that residents of most buildings consume more power than they should. This is mainly due to domestic appliances of several types that can now be found in most modern house holds.
I would strongly recommend a water audit and energy audit for your building. The results of such and audit will be a real eye opener.

Regards

S.S.Ranganathan
Advisor
Ion Exchange
Bangalore

7.

Dear Sai Kumar,

According to the statement, the total length of the piping is 70 meters. In this how much is horizontal head and how much is vertical height. Or if you can informs how many floors are there in his apartment we can calculate the required pipe diameter efficient pump and design the system and send.

Nevertheless, from your mail I gather some information and give answer. You have stated that for one year the bore will supplied water and after one year the yield got decreased. At the same time, you gives a statement when the bore well water is delivered into the sump the supply are good.

1. What was the electricity bill when the bore well water was used? How many fold or % it has increased.

May be now you are using both hand pump and bore well pump, may be you has to bear the cost of 3 times the horsepower use at present and hence you paying 3 times more bill.

2. Some amount of the bill increase definitely is due to increased total horse power of the pump.

You has changed your system from submersible pump to deep well submersible centrifugal pump a modified version. Submersible pump is an efficient current consumption system when compared to the centrifugal system. For the same horse power and for the same discharge the electricity bill will be 35 % more for centrifugal system. This is one of the reasons for his power bill.

Previously you were using only the one H.P. submersible pump for 24 hours now you are using both 2 H.P. modified Centrifugal and one H.P. submersible. Hence there is 235% increase in the bill will be there.

3. Now come to the core problem.

Your bore well discharge got decreased because of the scale formation in the delivery pipe. The complete delivery pipe has to be treated for descaling effects either by mechanical means or by chemical means. Mechanical means is a better as they can see the blockage and remove the white impediments scale with iron bars or they can replace the pipe itself if the descaling is not taking place.

For 2 H.P. submersible Centrifugal systems, the ideal pipe would be one and half inch throughout. At the most you can use one quarter of inch pipe. Other wise the friction loss will be more if the vertical head increases and for more total head.

Without going into to other details for 39 families, considering the requirement of 200 litre per head in apartment life, including guests and workers the water requirement is for about 250 persons and about 50000 litres is getting used in the apartment. IF there is no gardening it is all right.

This 50000 liters of water is getting pumped in 20 hours. Hence we can conclude that about 2500 litres per hour is the pumping. The rate of pumping is 42.5 litres per minutes. This implies that the efficiency of the 2 H.P. single phase centrifugal pump got reduced from delivering 120 lpm to mere 40 lpm; which implies that 3 time yield reduction.

If you change the diameter to a minimum one quarter inch we can reduce 50 % of pumping time. Hopping that the sump gets filled to its brim or the sump is able to supply about 80 to 90 lpm.

You have to change the delivery to higher diameter size to decrease the E.B. bill amount.

This is for your kind information.

With regards,

A.Rajamohamed Ambalam
Geophysicist

8.

1: The simplest explanation for increased power bill is, of course, earlier you were running only one pump whereas now you are now running two pumps.

2: Check the capacitors on both the pumps and ensure you aren't paying a higher bill due to low power factor.

3: While you need to clean up your delivery system, it is useful to understand the mechanics of it. Contrary to popular perception, increased resistance in the delivery system does not directly increase the load on the motor and hence the electricity consumption. Strange though it may seem, actually it decreases the load and the consumption per unit time. Suppose the delivery system is completely choked. Then the pump will simply churn the water around in what is known as “forced vortex motion” – like the milkshake being churned around in the liquidizer jar of your kitchen mixer. No water will be pumped up, hence no work is done, and the only electricity consumption is in various electrical losses - core loss, copper loss etc. and mechanical losses - friction of mechanical parts and friction of water with the inside of the pump.

The friction will be converted to heat, and you will recall it was exactly through such increase in temp. in “churning without pumping” that Joule established the “mechanical equivalent of heat”.

But the electricity consumption does increase. What happens is - increased resistance in the delivery system reduces discharge rate and to pump the same quantity of water you have to run the pump for longer duration. That is how the electricity bill increases.

Borewell water always has some sediment in it. In an apartment complex the horizontal portion of the delivery pipe is followed by a vertical portion. Pumping sediment up is more difficult than pumping water, and some sediment remains trapped in the horizontal portion of the pipe. Open the pipe just before the vertical section starts, and run the pump. I bet a lot of sediment will flow out.

Chetan Pandit

9.

Dear Mr. Sai Kumar,

Having gone through the details you have provided and also the suggestions that have been made we realize that:

The information of daily requirements of 40, 000 liters as a thumb rule for general estimation purpose is perfect.

The information regarding the open well pump that you have given- 2hp suction and delivery 1.25 inch etc.. suitable for 70 meters… this seems to be somewhat questionable

We have been in the business of installation and maintenance of pumps now for the last 20 years. And were interested in knowing which company open pump is delivering water up to 70 meters, as per what information we have regarding different pumps, (Flow vs. Head) to have a working head nearly equal to 70 meters the pump HP would be at least 7.5 .

It is possible that your submersible in the bore well has a working head of 70 meters, and that is why the mistake

Secondly the billing part
2 hp pump is 1.5 kw and 1 hp is .75 kw total of 2.25
2.25 kw per hour multiplied by 20 = 45 kw hr
45 kw hr multiplied by Rs 3 = Rs135 /- day
Rs135 /- multiplied by 31 ( days) = Rs 4185 /month or around this amount

Even if you had a 5 hp pump and it worked for 20 hours ( which is next to impossible) the costs would be only around 5580/- per month. Hence I think that there is some major mistake may be the meter itself has gone bad.

What ever may be the discharge of the pumps (important to calculate out actual usage of water) from what details you have provided regarding hp and pipeline etc..
Under no circumstance should your bill go beyond 6000/-

Coming to the part of the pipe diameter- well reducing the diameter on delivery side does increase the delivery head but it is relatively insignificant when one is looking at what is the kind of discharge one is getting in OHT ( aprox 2000 lph in present case)

Ideally speaking the bore well should directly deliver water to the overhead tank, but there should be no continuous pumping. 4-5 hours of pumping with a break would be ideal.

The open well in the sump should be reserved for pumping corporation water only.
To help in boosting the water from the bore well- one can attach a small ½ hp or 1 hp pump in series on the submersible pump delivery pipe (with minor modifications), only care to be taken is that this pump to be started 10 minutes after the submersible is switched on. This results in saving on double pumping, and works provided the bore well does not run dry.

Ideally in your case, where the pumps are of low discharge capacity, it would be ideal if you could install a multi-tank , multi pump level controller system. With level controllers in the sump, Bore well and the OHT.

In the initial period till the OHT tank is full to capacity one needs to ask the residents to keep their water shut. May be half a day, once that is done as soon as the OhT is full the pumps will stop and as soon as about 15 cm of the tank is emptied the pumps will start and top it up.

Naturally, in such situation one has to ensure that no leaking taps or flush tanks are there within the building.

We would like to help out with the problem of water management but we require more information regarding
Yield of well, aquifer depth, present pumping water level in borewell, elevation of OHT, length of pipeline with number of bends etc. from sump to OHT, submersible Pump manufacturer, Pump type, Number of impellers- if you can provide us with all or a part of this information we may be in a better position to help.

Mr. Bharat Mane & Dr Anil Lalwani
Well & Water Works Pune
Ph. 25652486, mobile 9822292545, 9422084073
Bhrtmane@yahoo.com

10. Single pump for both sump and borewell?

We constructed a bore well and a sump for municipal water. Borewell is of 90 feet depth and sump is of size 8*4*6 feet. We have a 1 hp jet pump for bore well currently. This pump takes water from bore and pumps to the overhead tank.

Can I use this pump as a common machine, taking water from both borewell and sump to overhead tank? Or should I have two different machines for both? If it is a common pump, what will be the circuit diagram for water transport?

Thanks in advance
Regards
Srinivas

11. Need suggestions for selection of openwell submersible pump

We are in the process of buying newsubmersible pump for the openwell  in our society
1. The UG tank depth is 3m
2. Building height is 44m
3. Upper storage tank height is 6m That means total height is 53m.

We have selected Kirloskar openwell submersible horizontal pump (Model KOS+). It is 7.5KW. Delivery is 64m. It requires 2" delivery pipe which is there.
Please let me know whether our selection is correct. I would also like to know the minimum required hight of first bend on delivery side from the pump.

Thanks & Regards,
Sachin Sanas

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