Is it time to switch my Jet Pump to a Submersible Well pump?
Many homeowners scratch their heads when looking at their water pump and wonder if there is something better. In this blog we will discuss the different operation principles between a jet pump designed to pump water out of a well and a submersible well pump. Once we understand the main differences we’ll discuss the pros and cons of switching your surface pump out for a submersible pump.
Submersible Well Pump Operation and Setup
Submersible well pumps (like the one pictured to the right) are designed to be submerged in water, often very deep and are usually long, narrow and cylindrical so that they can be installed in 5” or 6” well casing. A submersible pump is composed of a motor on the bottom and the pump on the top. The water is sucked in at the screened gap in between the pump and motor. The pump typically has several impellers that turn the centrifugal force of the spinning motor into water pressure and flow that is directed out the top of the pump. Submersible pumps are installed in a well with a pipe that goes down the well and connects to the top of the pump where water is discharged. A wire goes down to the submersible pump to supply electricity to the motor. Submersible pumps are selected based on the flow and pressure required and can be installed in shallow wells of just a few feet deep or in wells over a thousand feet deep!
Jet Pump Setup and Operation
Jet pumps are similar in that they have a motor that spins one or more pump impellers to cause water to flow under pressure. In the photo to the right the motor is on the right while the pump is on the left. Jet pumps are located near the top of the well and “suck” the water out of the well. Shallow well jet pumps have a single pipe that goes into the well can suck water from a depth of 20’ maximum. Theoretically, water can be sucked up to a maximum of 33’, however for practical purposes and maintaining some level of efficiency, pumps are usually limited to about 20’ of suction lift. Beyond the theoretical maximum of 33’ of depth to water, the high level of vacuum from the pump sucking the water up means that the water will actually start to separate and large bubbles of “nothing” will develop! Vacuum bubbles!
Deep well jet pumps were developed to overcome the limitations that only allow standard jet pumps to suck water from shallow wells. Deep well jet pumps have two pipes that go down into the well and are capable of pulling water up from depths of several hundred feet. Deep well jet pumps do this by recirculating a large quantity of water back down the well to a jet assembly that has been installed at the bottom of the two pipes in the well. The jet assembly has a water intake on the bottom and a nozzle and diffuser that the recirculated water is force through to create a vacuum to suck water in from the suction intake. This water is mixed with the recirculated water from the top and is then pushed to the surface.
Efficiency Pros & Cons
Hands down submersible well pumps win the efficiency contest. EVERY SINGLE TIME. Why? There are several reasons. The water recirculated by jet pumps to extract water from deeper wells uses a significant amount of additional energy and there is much more resistance to water flow, or friction losses, because of the additional length of pipe required in this type of system. (Remember, two pipes are required one for the water going down to the jet assembly and another, larger pipe, to bring the recirculated and the additional sucked up water back up the well.) This recirculated water and additional friction loss require energy that is simply lost to the environment. Submersible pumps are installed in the water down in the well so the limitations on sucking water do not apply and recirculation is not necessary. Every gallon (or liter) pumped by a submersible well pump comes out of your faucet while a deep well jet pump may need to pump and recirculate 3 or 4 gallons of water for every gallon that comes out of your faucet!
All things being equal, submersible well pumps use significantly less electricity to do the same job as a jet pump does. The more water you use, the more significant this difference will become. With energy prices and demand increasing, a correctly selected submersible well pump is a long term investment that will save money!
Noise Pros & Cons
Submersible well pumps are underground by tens or even hundreds of feet and make very little noise. These two factors combined mean that there is very little or almost no noise. Jet pumps are mounted on the surface and, while not exceptionally noisy, they are easily heard with combined sounds of the motor and hiss of water recirculation within the pump.
Priming Pros and Cons
Centrifugal type water pumps are not designed to pump air and if there is air in the suction or supply pipes the pump will not pump any water. “Priming” refers to ensuring that the pump and the pipes supplying the pump are full of water so that they operate properly. Jet pumps and deep well jet pumps must be filled with water before they can operate. Submersible pumps do not require priming because they are submersed in water! Jet pumps often loose prime if there is a small leak/they have been shut off for a period of time due to lack of use or a power outage. While priming a centrifugal pump is not a difficult process and takes about 5-10 minutes with the correct tools, it is a bit of a hassle that most people do not want. In most cases it involves getting a wrench, removing a pipe plug and using a funnel and bucket of water to fill the pump/pipes, then reinstalling the pipe plug that was removed. Most people find that they have to prime their jet pump at the most inopportune times. In the morning when they wake up and want a shower or when they get back from a trip late in the evening and need to use the water. In some cases, jet pumps are damaged when they ‘loose prime’ because they need the water for lubrication and cooling and may run ‘dry’ if they don’t have the proper protective devices installed to turn them off when there is a loss of prime. If jet pumps turn on and run without water in them damage to shaft seals and other components can results. Submersible pumps don’t need this type of babysitting/priming because they are immersed in water! (Low water protection is a good idea even for a submersible well pump to ensure it is not damaged if the water level in the well drops for some reason.)
Simplicity & Cost of Installation Pros & Cons
Shallow well jet pumps and submersible pumps are both simple and straight forward installations with a single pipe going down the well. Deep well jet pumps get a bit more complex dealing with two pipes. Most pump installers are not fans of servicing or installing deep well jet pumps for this reason. Cost of Installation for Shallow well jet pumps and submersible pumps are roughly equivalent, but two-pipe deep well jet pumps can cost significantly more for installation as they require a second pipe, the jet assembly and significantly more time to install and commission.
Maintenance Pros & Cons
While submersible pumps are maintenance free, if there is a problem with the pump or motor, they must be removed from the bottom of the well for service. The pump and motor are generally sealed at the factory and not considered serviceable. Old, worn out submersible pumps and motors are typically sent to be recycled and new units are installed when there is a problem. Jet pumps are on the surface so they can be more easily repaired or replaced without having to remove equipment from the well. Jet pumps use serviceable motors that can easily have start switches and bearing replaced as needed. It is recommended, however, that the pipe and jet assembly are inspected when a deeps well jet pump is serviced. The jet assembly may have mineral deposits or corrosion and the piping needs to be inspected for corrosion or plugging with mineral deposits. With these considerations in the comparison, submersible pumps are faster/easier to remove and install and will likely cost less in overall maintenance than a deep well jet pump.
So I should just use a submersible well pump, right?
For pumping from a well, submersible well pumps are definitely a cost effective, simple and efficient choice! If you want to pump water from a storage tank, using a submersible pump is and option, but centrifugal pumps should certainly be considered in these cases as they are easily maintained and don’t have some of the constraints that submersible pumps do! When pumping from a tank, centrifugal pumps don’t have priming issues or need to recirculate water so they don’t have the efficiency losses that are associated with pumping from a well. Manufacturers of submersible pumps frequently require that they are oriented vertically and installed in a flow sleeve to ensure proper cooling/operation! This may mean that you loose the bottom few feet of storage tank capacity! In a well this isn’t a big deal, but with a storage tank this can often represent a thousand gallons or more of lost capacity. A centrifugal pump will allow you to use all the water from the storage tank without a problem.
Summary
Submersible well pumps are the efficient and simple choice for most well applications while centrifugal/jet pumps are great if you want to pump water from a storage tank! If you are trying to look at pumps online and sort out some of the confusion, you might check out this article. If you are trying to select the best/most efficient pump for your well application, check out our blog on this topic here.
Our team at Oakville Pump Service is comprised of an amazing team of qualified water system designers and installers that can help you with your submersible well pump equipment, water tank or other water needs. Contact us today!
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