A Practical Guide to Water Treatment Pumps

Let's face it. Pumps aren't the sexiest items in our product catalog. It may be hard to get really worked up about them, but without pumps, water treatment as we know it wouldn't be possible.

Pumps play many roles in water treatment. They move water from one place to another, and they provide added pressure that's sometimes needed to perform treatment functions. Pumps are used to inject water treatment chemicals, to supply compressed air, and to move treated water to its point of use.

Pumps usually rely on electricity for power, but two of the pumps discussed below use the water being treated as their energy source.

The pumps below are representative of the many styles of pumps used in standard residential water treatment. We'll explain each as we go.

RO Booster Pump

The function of the RO booster pump is to increase the pressure of reverse osmosis feed water. Reverse osmosis is a pressure-driven treatment. Increasing the inlet pressure improves both the product/reject efficiency and the quality of the product water (TDS). Conventional residential RO units can run on as little as 40 psi, but they perform with much greater efficiency at 60 psi or above.

The pump shown above is an Aquatec 6800. With factory settings, it runs small RO units at around 80 psi inlet pressure regardless of the pressure of the source water.

The slightly more powerful Aquatec 8800, which looks identical, is used for RO units with membranes that produce more than 50 gallons per day.

The total “pump package” consists of the pump, the transformer, and a tank pressure switch.

Delivery or “Demand” Pump

The “demand pump” looks much like the booster pump but its function is completely different. Demand or Delivery pumps are used to send water from a low-pressure or no-pressure source to another location.

You'll note that there is a pressure switch mounted on the head of the pump. When there is a “demand” for water, like the opening of a valve or a faucet downstream, the pressure on the switch goes down and the switch turns on the pump. When the demand goes away (the faucet is closed), pressure builds in the switch and the switch turns off the pump.

Small demand pumps are useful tools. Here are some examples of how they are used:

  • To send water at increased pressure from an undersink reverse osmosis unit to a distant refrigerator or icemaker.

  • To send water to an aquarium tank from a storage tank.

  • To send water from a non-pressurized storage tank to the customer's bottle in a water vending machine.

Pumps in this category typically deliver water at rates of about 0.5 to 1.5 gallons per minute.

Repressurization Pump

The sophisticated one HP Grundfos repressurization pump is actually in function a much larger version of the small demand pump. It delivers water on demand to homes and other large applications. The quiet, smooth operating pump has its own small built-in pressure tank to assure smooth, instant delivery of water upon demand. It functions without the added pressure tank that is normally used with well pumps.

We offer this pump as part of a “whole house option” package that consists of all the parts you need to send water from a non-pressurized reverse osmosis holding tank to the home. When a demand is made for water in the home, the powerful but sensitive variable-speed pump comes on to supply it.

Chemical Feed or Injection Pump

The Stenner variable speed injection pump feeds liquids at a very slow rate but at high pressure into a water pipe. It is used for a variety of purposes. For example:

  • It feeds chlorine to kill bacteria or to oxidize iron or hydrogen sulfide.

  • It feeds soda ash to raise the pH of acidic water.

  • It feeds polyphosphate to “sequester” iron or hardness.

  • It feeds hydrogen peroxide to oxidize hydrogen sulfide or iron.

It can also feed combinations of chemicals, making it a very handy tool for treatment of water that has multiple problems.

It is unique among the pumps on this page, being a “peristaltic”-style pump that works by squeezing a flexible tube with a roller.

The lowest output Stenner pump that we offer can feed solution at the very slow rate of 0.2 gallons per 24 hours.

Pumps of this type are often also called “metering” pumps.

RO Permeate Pump

The Aquatec Permeate Pump is a unique device that significantly improves the economy and performance of small reverse osmosis units. It functions by storing the hydro power from the RO unit's drain water stream and using this energy to force product water (permeate) into the RO unit's storage tank. It frees the reverse osmosis unit from the need to contend with back pressure from the air-pressurized storage tank. The result is that the RO tank fills faster and the unit uses less drain water and produces better quality water.

The permeate pump is one of the most significant improvements in RO technology in recent years. Its cost is modest, and it can be added to most existing RO units.

Water-Driven Injection Pump

The Chemilizer non-electric injection pump feeds solutions of chemicals like chlorine, soda ash, polyphosphate, and hydrogen peroxide into a water stream using only the energy taken from the flowing water itself. It fills many of the functions of the electric Stenner pump above, but it requires no electrical connection.

The pump is a small white appendage at the bottom of a large blue “water motor” that supplies the power. As water flows through this blue water motor, the motor turns the pump which picks up the treatment solution from a solution tank below it and pressure-feeds it into the water line.

This injection system has the advantage of feeding at varying speeds into a stream of varying flow rates. The faster the water being treated runs, the more of the treatment chemical is injected.

This pump is a very fast feeder, injecting at a 250 to 1 ratio. For every 250 gallons of water that passes through the water motor, the pump injects a gallon of solution. This high rate of injection means that most commonly used chemicals, like chlorine, have to be diluted heavily to avoid over treatment, and some very concentrated chemicals, like Spectraguard, just won't work with this pump.

Air Pump

The small compressor or air pump injects air into a treatment tank. The water being treated falls into the treatment tank where the compressed air oxidizes the iron and hydrogen sulfide, making them easily removable by the filter that follows. The air pump is quiet, dependable, and economical to operate.

Booster Pump for Larger RO Units

A Procon Carbonator Rotary Vane pump attaches to an electric motor to provide high pressure water for large reverse osmosis systems like our Watts R-12 Units. The pump can easily run the RO unit at pressures upward of 200 psi.

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