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Compressor Vs Jet Pumps

Most of us are not aware of a type of domestic water pump called the Compressor pump. I had come across this noisy pump a couple of year ago. The operation of this pump is very simple and powerful though it is noisy. The pump consist of a Air Compressor and a nozzle. See that’s all. Remember in jet pumps we would have an Impellor and a Jet (a form of nozzle). Compressor jumps compresses atmospheric air and pressurized that thru the nozzle which creates a back pressure to pull water for far depths to the surface and above. The advantage is that the compressor (motor + compressor) is no way connected to water drawing system other that at the nozzle. Whereas in jet pumps water is drawn by the back pressure created at the impeller’s center (radial flow) which makes it apparent that water is always in touch with the motor + impeller system. In jet pumps there are two pipes down to the water level one for drawing and one of recycling. Jet pumps push a portion of drawn water downwards to create back pressure at the jet-nozzle. Water flows from bottom to impeller, impeller to top, impeller to bottom again. In compressor pumps, the since air is pushed downwards water flows only from bottom to top.

In a compressor pump, the flow of water does not start immediately because the water starts flowing only after a certain amount of pressure is built at the nozzle. Also the flow of water is not uniform typically the pump pushes gush of water in regular intervals of time at like a jittery saw tooth waveform. Since a compressor is needed, these pumps are noisy. In a Jet pump, the water flow is more or less uniform and the water pumping starts immediately once the pump is switched on. Here water level is maintained in the delivery pipes and also at the impellor system. Jet pumps are almost quite when all the bearings and move parts are properly lubricated.Disadvantages are found in both systems. In a jet pump, water is always expected to be maintained at the impellor system. The water level is maintained by a spring driven valve at the jet below water level. During the passage of time, this spring and valve gets damaged which is defy the requirement of impeller water level. So one has to fill in water everytime to start the pumping action. Jet pumps dont work at all when there is a lot of slime around the jet or if the valve is stuck due to any particles near it.

In a compressor pump, if there is a leak in the downstream air flow, water pumping does not happen as the pressure could not built at the nozzle. When the strength of the compressor falls below a threshold again the water pumping stops for the same reason. These pumps are very noisy (both reciprocating and centrifugal). The pumps needs regular maintainance as they have more mechanical moving parts (basically the compressor oil needs to changed on a regular interval). Also, upstream water flow should not be blocked completely which would affect the nozzle, so it is not possible to close the gate valve in the upstream when the pump is running. Whereas the upstream
of jet pump can be completely shut even when the motor is running.

Compressor pumps are more suitable for borewells with depths of range 200+ feet. Jet pumps are more suitable for wells and sumps. Compressor pumps can work even when there are dirt or dust in the water as the pressure at the nozzle would push them away from blocking the channel. Jet pumps are good when the nozzles are suspendable well above the surface level in the well. In the case of bore well, jet pumps are fine if casing is done for the entire depth. Compressor pumps are atleast 1.2 times expensive than Jet pumps in Chennai.In general when you go for deeper borewell, it is always adviced to go for pvc continuous hose pipes instead of discrete pipes with joints. It serves two purposes. 1) Maintenance is easy as it would relatively very easy to take out the entire hose out of the bore as you can roll it. 2) Two many joints in the upstream/downstream deteriotes the performance of the pump.

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  1. Sreenivasa Prasana
    June 14th, 2011 at 10:46 | #1

    Nice comparison. very informative.

  2. Murumuth
    June 30th, 2011 at 00:08 | #2

    very good article..

  3. Bhaskaran
    May 30th, 2013 at 11:08 | #3

    useful information when deciding motors.

  4. ramesh
    September 14th, 2013 at 14:50 | #4

    Good technical advice. But still people should know and opt for the better to best advantage of compressor pump when compared to Jet or Submersible pump. Compressor need less maintenance that is only to check and refill the lube oil. Rest is totally Rest and works for ever. The Equipment resell value is good for compressor pump. One can recover 70% cost back.

    Ramesh 944………………..

  5. Thangavel
    July 21st, 2014 at 17:59 | #5

    Very practical and well explained.
    I’d like know about the roll of the adjustable valve fitted on the delivery pipe in the Jet pump as I’m planing to connect a water softener on the delivery line. It would be be nice if if share the knowledge.

    Thanks!

  6. sudarsun
    July 21st, 2014 at 19:05 | #6

    It is not a regular valve, but a non-return control valve aimed that retaining the water between the non-return valve and the foot valve (priming). The jet pump should be primed (filled with water) for it to work. So, the non-return valve ensures that the water in the impeller section does not get drained away, when the delivery side is lower than the pump’s level.

    You may connect a water softener, but it would be better to check the parameters of the device before installing. Basically, the time required for the softener to work on the water should be quick enough that delivery water get treated sufficiently. The best other option is to fit the softener on the delivery side of the overhead tank, where the water flow is slower than on the delivery side of the pump.

  7. Thangavel
    July 22nd, 2014 at 19:50 | #7

    Thanks for the quick reply though your post is more than 5 year old:)

    I think i got the point from your reply. I just capture an image from internet and circled that valve (just to make sure we are talking same valve).

    In my apartment, the Jet pump (1 hp, Taro make) delivers the water to the sump which is lower than the pump’s level. And we run another 1.5 hp mono block pump to lift the water from sump to overhead tank on 4th floor. In my neighbor’s apartment, they use 1.5 hp jet, Suguna make) and the water delivered directly to overhead tank on the 4th floor. I got surprised because the water pressure or flow from the our bore to sump is very low. When you see the delivery, you won’t get the feeling that it can lift even one floor. Our bore-well depths is 100 feet. I’m not sure about our neighbor’s bore-well depth but it should be between 60 to 100 feet. I don’t think 0.5 hp difference takes the water to 4 floors. I guess, in my neighbor’s pump, they might have opened the pressure (non-return) valve fully and in my apartment it’s mostly closed since the delivery sump is lower than the pump level. am i right?

    I think I can connect the softener just before the delivering to the sump. Anyway I’ll check the presser & flow limits of the softener (we just received the softener from Aquionics today which we planned to install on Saturday ) and will share the details.

  8. sudarsun
    July 23rd, 2014 at 21:35 | #8

    40 feet depth difference (yours being 100 and your neighbour’s being 60) is significant while comparing the throw of the pump. Ideally, the suction length should be as small as possible, as it is harder to maintain vacuum. please anyways check your impeller condition and also the foot valve for correct functioning.

    The valve that you have highlighted (thanks for the picture; a picture speaks a thousand words!) is just an ordinary gate valve (not the non-return type). This valve is used to control the pressure developed by the motor. You need to change the valve opening for taller heights, basically the valve regulates the pressure difference between the suction and delivery of the pump, which is critical for maximizing efficiency of the pump.

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