How does permeate pump work

The average membrane rating is based on a constant feed water pressure of 50 psi using 77 degree water. The end result is that your RO system is drastically under-performing because of lower pressure and water temperature. To make matters worse, the pressure storage tank that stores your RO. This pressure is fighting the inlet water pressure water coming into your RO system from your tap water source.

The inlet water pressure is trying to force water through the RO Membrane and into the tank. Even if you have good incoming water pressure of 60 psi, as the tank gets close to full, the actual pressure on the membrane is only 20 or 25 psi because of the off-setting pressure from the storage tank.

This will result in reduced permeate good water production and vastly increase the flow of water to the drain. A permeate pump will improve water quality through better membrane efficiency. In the typical RO system, increased tank pressure causes decreased pressure across the membrane. This decreased pressure causes a substantial decline in system performance and efficiency.

A Permeate Pump enhanced RO system maintains full pressure across the RO membrane, even as tank pressure reaches its maximum levels. This reduced back pressure from the storage tank ensures better water quality maximum TDS reduction , longer filter life and extended membrane life.

Many versions of a "water on water" undersink RO have come and gone over the last two decades. In this system, the RO unit produces into a flexible bladder inside an unpressurized tank. When the user opens the faucet, untreated tap water rushes into the tank to squeeze the bladder and force treated water out through the faucet. The early models of the water-on-water units had numerous problems and soon went away.

The water on water style, even if it works perfectly, consumes an amount of water equal to the permeate to push the permeate out of the tank. New water on water systems keep appearing from time to time. We'll see. A current new "water saving" design called "zero waste" uses a conventional bladder tank but employs an electric pump to pressure the RO unit's reject water back into the home's water supply.

In my opinion, "zero waste" ranks high on the list of the world's worst ideas ever. The much-cursed, inefficient, but very reliable bladder tank still dominates the market.

It is still on top because it is simple, essentially problem free, and relatively inexpensive. The permeate pump was created to overcome the inefficiency of the bladder tank RO system. Unlike electric "booster" pumps, which increase the water pressure going into the RO unit, the permeate pump takes energy from the RO unit's drain water stream and uses it to overcome the back pressure from the storage tank.

It allows the RO unit to produce its "permeate" product water into a pressure-free chamber of the pump rather than directly into the pressurized tank itself.

The unit's reject water, or "brine," is used to provide energy which is stored and used to push the permeate into the storage tank. This nifty graphic supplied by permeate pump manufacturer Aquatec shows how the pump works. The permeate pump relies on a simple design. The pump runs without electricity and is completely automatic. It can be installed with a hydraulic shutoff as in the graphic or without one. Without the shutoff valve, the pump itself shuts off the RO unit's production when the storage tank is full.

Larger image. Reverse osmosis is a pressure-driven process. In simplified terms, if an undersink RO unit is fed with 60 psi inlet pressure, it runs wonderfully when its faucet is open and it isn't putting water into the pressurized storage tank.

However, when the faucet is closed and the RO unit is filling the storage tank, it does not enjoy the advantage of the full 60 psi. When the tank is partially full, for example, and has 30 psi pressure, the RO unit must use 30 of its 60 psi just to overcome the back pressure from the tank and it is running very inefficiently.

Unlike electric pumps that boost inlet pressure to reverse osmosis units, the unique "permeate pump" enhances performance without actually providing additional pressure for the inlet side of the unit. The permeate pump, instead, greatly reduces the back pressure from the RO unit's storage tank. This allows the RO membrane to take full advantage of the pressure that it has.

Permeate is water treatment jargon for the product water of the reverse osmosis unit--water that has been treated by the membrane, the water you're going to drink. Brine is the rinse water, the water that is carrying away the impurities rejected by the membrane, the water that will ultimately go down the drain. The pump works by storing the hydro power of the brine, the reject water, and using that energy to power the permeate under pressure into the unit's storage tank.

The result is a quite remarkable increase in unit efficiency. Since the RO unit can fill the tank much faster without the hindrance of back pressure, far less reject water is used, and the permeate, or product water, is purer. The compact, grapefruit-sized pump mounts to the undersink wall with a clip that's provided. It must be installed with the indicator arrow pointing up, as shown in the picture. On our permeate pump units, we color code the tubing for easy installation. Brine In. Black Tube.

Water leaves the membrane housing's brine port and goes to the pump, under pressure. Its flow is limited by the RO unit's brine line flow restrictor. Brine Out. Permeate Out - Orange Tube: Powered by the stored energy from the brine, the permeate water is forced into the unit's pressurized storage tank via the orange tube. The brine is as important a part of the RO final product as the permeate itself.

The brine performs the essential function of carrying away the impurities and keeping the membrane clean. More about permeate pumps and ordering information. Please type in your e-mail to receive our newsletter, The Pure Water Occasional. How Permeate Pumps Work.

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