Energy Efficiency & Savings FAQ’s

Are Jet Pumps or Submersible Well Pumps more efficient?

The key to this question lies in the difference between how high water can be sucked “up” with a vacuum and how high water can be pushed under pressure. Imagine that you have a really long straw and you’d like to take a drink from your well. While you may not have the physical ability to take a drink from deep in your well, theoretically you should be able to suck water from about 33’. If you try to suck water from a depth greater than that, the weight of the water starts creating a vacuum of empty bubbles that prohibit water from flowing up your straw. In real life pumps can and do “suck” water out of wells, but this is usually limited to about 15-20 feet because of the loss of efficiency most pumps experience when trying to “suck” water.

On the other hand, if you want to send water to the highest skyscraper/mountain there is no theoretical limit to the pressure you can generate to “push” the water. While your mouth may not be able to produce enough pressure to blow water up a straw that extends from the dead sea to Mt. Everest, the limitations of a vacuum do not apply. The limitations are in the strength of the materials in the pipes and pumps to contain the amount of pressure required to pump water from the dead sea (the  lowest place on earth at 1388 feet below sea level) to the peak of Mt. Everest (29,029 ft above sea level)…about 13,000 PSI. There are high pressure pumps that make more pressure than this in special applications for water jet cutting or hydraulic applications.

Jet pumps creatively get around the 33’ limitation by putting two pipes down the well and utilizing a venturi. A venturi creates a vacuum when fluid flows through it. So a jet pump pushes water down the well with the “drive” pipe which creates a vacuum as it passes through the venture way down below. This vacuum sucks some water from the well and the pushes it with the recirculated water back up to the top. Some water is stripped off and some is sent back down. This is extremely creative, but very energy intensive as several gallons of water can be recirculated for each gallon of water drawn from the well. Jet pumps have to have water in all these pipes in order for this process to work, hence the term priming the pump. A pipe (stinger) with a one way valve is usually attached to the very bottom of the jet assembly. This valve allows water to go into the jet assembly, but not back into the well. This foot valve helps the Jet pump system remain primed. If one of those multiple pipes or joints leak, well, they all have to come out and the leak found and repaired before the pump will work properly again. Jet pump installation is an engineering effort. The Jet pump must be properly chosen and the jet assembly properly sized with the correct nozzle and venturi that matches well depth and static water level. The jet assembly with two pipes is sent down the well, which usually requires at least two or three people for installation on deeper wells. Once installed, the jet pump must be primed and the recirculation control valve dialed in. The list of parts for a Jet pump include: pump, control valve, jet assembly, venture, nozzle, foot valve, drive pipe, stinger pipe and suction pipe. Jet pumps are installed less and less frequently and availability for the pumps and parts is getting further and further out because of their inherent disadvantages.

The modern submersible pump uses about half the amount of energy that a jet pump would to pump the same amount of water. It does this by hanging the pump and motor down in the well with one discharge pipe and a power cord. The pump doesn’t have to suck or recirculate water, it doesn’t require priming, it just gets to push it up out of the well. It most cases (hot water wells excluded) the water in the well keeps the motor nice and cool. Even if there is a small leak in the pipe down the well, it doesn’t usually stop the pump from delivering water. Submersible pumps also offer the advantage of relative silence because the pump is many feet underground where you don’t have to listen to it run. Submersible pump installations are much simpler and often cheaper than an equivalent Jet Pump installation because they only involve a few main components: Pump, Pipe, Check Valve & Wire. While it does involve selecting the correct components, the selection process is much simpler than for a jet pump.

So hands down, submersible well pumps win when it comes to not just efficiency, but simplicity and ease of installation as well!

Do VFD’s save energy, are they greener?

Variable Frequency Drives are a type of controller that allow a pump to be run and the exact speed necessary to produce the exact amount of flow/pressure required. These devices are commonly marketed as energy saving devices and, in some select applications may provide some small energy savings. These systems are typically more expensive and more complicated, but do offer some very nice features that can include reduced pump noise, reducing water hammer/surge, extended pump life, & constant water pressure.

The primary reason that VFD’s don’t provide energy savings is the parasitic energy losses inherent in the technology that involves rectifying the AC voltage from the grid and then re-inverting it to the correct voltage/frequency for the motor’s reduced speed. This conversion process involves electrical resistance and heat loss!

In side by side bench tests conducted by OPS for over a week on a conventional pressure switch/pressure tank type system as compared with a VFD system (using the same exact pump & motor, with the same exact varying flow rates and volumes) resulted in a net zero energy savings. 

“Constant” pressure is a bit of a misnomer as these systems do hunt a bit, but not nearly as much as pressure switch type systems. For the most part, most people simply cannot physically tell the difference between a constant pressure and traditional type system at the faucet/in the shower or at the hose-bib in the garden.

Applications where variable frequency drives are rarely called for include systems where a pump directly fills a storage tank, pond or other vessel and the flow rate/pressure is not important at all.

Variable Frequency Drives are really not any more or less green than the alternative system unless they can significantly reduce the quantity/size of pressure tanks required. Typical pressure switch controlled systems require enough pressure tank volume (supplied by pressure tanks) in the system so that the pump cycle time does not exceed manufacturer specifications. A VFD can typically reduce this requirement to one medium/small sized pressure tank. On large systems the savings in pressure tanks can easily pay for the additional costs associated with using a Variable Frequency Drive and reduce the physical/carbon footprint of the equipment necessary for installation.

Can I reduce the amount of electricity my pump uses?

Yes! Here are a few ways you can reduce the amount of energy to pump water:

1) Pump your water as efficiently as possible. Not all pumps are created equally nor are they created for the same job! Pump A may be able to pump water at the same pressure and volume as Pump B. Pump B, however, utilizes a high efficiency motor and has been hydro-dynamically engineered to reduce internal energy losses and has been sized to operate in it's peak efficiency range for your specific application. Pump A is 50% efficient and Pump B is 70% efficient when you compare the amount of electrical energy put into the pump to the amount of mechanical energy output in the water. In real world terms pump B uses significantly less power to do the same thing that pump A does. One of our recent customers saves over $3000/year in electricity by simply changing to a pump OPS helped them select for the application.

2) Pump your water as few times as possible. Many water systems include many pumps that pump the same water multiple times. Take, for example, a system OPS helped revise at a large Hospital. As you read, note the number of times "pumped" is used in the description of the old system. 
“Water comes from springs located up in the foothills and travels in pipes to the hospital where it is stored in an underground storage tank. The water was then pumped to a second underground storage tank where it was then pumped up to an elevated storage tank. From the elevated storage tank the water gravity feeds the hospital compound and then travels down hill to a nursing school where the water was held in an underground storage tank. This water was then pumped to a second underground storage tank from where it was then pumped to another elevated storage tank.”
For users at the very end the water was "pumped" FOUR times! The tragic part of this scenario is that the water would never need to be pumped even once if the water system had been properly laid out or installed in the first place! OPS was able to cut the number of times the water was pumped down to two because complete system replacement was not feasible. Are there ways that your water system can utilize gravity or modify operations to eliminate unnecessary pumping?

 3) Waste less water. Wasting water comes in the form of several areas. Leaks are one of the biggest culprits. A dripping faucet can waste 5 gallons of water a day! A hose not completely turned off can waste 500 gallons per day! Leaky underground pipes are sometimes responsible for leaks on the order of thousands of gallons per day. To find leaks in your system, you need to strategically locate one or more water meters, make sure you aren't using any water and check the meter to see if it is showing water movement. You can also check for leaks in your well water system with the use of a pressure gauge. Make sure you don't use any water for a given period of time, watch your pressure gauge and if it goes down over that period of time, then you have a leak!

4) Use less water! There are several areas in which water may be reduced. Irrigation water is usually one of the highest water consumers. Check with your landscaper and slowly start reducing watering times/frequency and monitoring plant health. Utilizing mulch in cultivated soils significantly increases water retention and can reduce water needs. Install plants that require less water or none at all. You can also install shower heads, toilets and sink faucets that flow at much reduced rates. Don't run a load of dishes in the dishwasher until it is full, and when you run a load of clothes in the washer, make sure to adjust the load size to the actual load you are putting in. Running the machine on the full setting when you have only half a load can waste a significant amount of water and energy.

5) Pump your water in off peak electrical demand periods. While this may not save electricity, it can help you save money if you are charged different rates for “on peak” and “off peak” power usage. If you have tried the previous methods to reduce water usage and are after some additional cost savings, off peak pumping may be your next step, especially if you have a water storage tank. This scenario involves pumping your water to storage tanks in the night and mornings and then using water from those storage tanks during the on-peak demand hours when electricity is much more expensive. You system needs to be reviewed and analyzed to see if it can benefit from such a scenario.

How does the water I use impact my electricity bill from PG&E

If the water you use comes from a municipal water supply it may not impact your electricity bill at all. Your water bill is directly impacted though! Typical municipalities build the cost of the electricity it takes to pump, treat and monitor the water they provide into their consumer rates. The more water they must provide, the higher costs, the higher your rates. Did you know that current data indicates that 40% of all energy consumption in the United States is utilized in pumping water!

If the water you use comes from a well and pump then your electric bill is dramatically impacted by how much water you utilize. Look on your pump controller(s) and find out how many horsepower (HP) your pump is. Factors such as: the more pumps you have, the larger the horsepower, the longer they run and the older/less efficient those pumps are add up very quickly!

Sometimes customers call and ask us to check their submersible well pump system because they just got a massive bill for electricity from PG&E. In many of these cases old metal pipes have deteriorated and are leaking causing their well pump to run constantly!