How a Permeate Pump Works with a Reverse Osmosis System

What is a permeate pump?

Reverse osmosis (RO) systems use a permeate pump to save water that is sent to the drain and enable maximum system performance. An RO system with a permeate pump produces higher-quality water at a significant flow rate. Up to 80% less water is wasted when a RO is fitted with a permeate pump.

What is permeate in reverse osmosis?

Permeate, in terms of reverse osmosis, is the clean drinking water that is left over after RO membrane filtering. The ability of the permeate pump to speed up the generation of clean water during reverse osmosis gives rise to its name.

The permeate water is removed from impurities by the reverse osmosis membrane. The pollutants are carried away to the drain by the RO reject water, also known as concentrate or brine. To show that potable water and unclean water have been separated, permeate pumps include labels that read "brine in" and "brine out" at the input and exit.

How permeate pumps work?

In order to move the permeate to the RO storage tank, the permeate pump stores the brine or reject water from the RO process in a chamber and utilizes it as energy. The permeate water is pumped into the storage tank by a piston that is activated when the drain water rises in the pump. The system performs better as a result of this procedure, which stops the water pressure in the tank from pressing on the RO membrane.

Each side of a permeate pump has an intake and an output for permeate and brine. The energy required to move the water to the storage tank is provided by the brine.

“Brine in": The left side of the pump is where reverse osmosis rejects water gathering.

"Brine out": refers to the process where the brine enters the pump, provides energy, and exits down the  drain.

"Permeate in": The inlet is where the membrane's permeate flow gathers.

"Permeate out": Driven by the brine's energy, the permeate leaves the pump and moves toward the storage tank. 

Permeate pump diagram

RO permeate pump vs. RO booster pump

When the water pressure is too low for the RO membrane to function, a RO booster pump raises it. Permeate pumps are designed to assist reverse osmosis systems in saving water, not to increase water pressure or deliver water. While the permeate pump ro system increases the efficiency of reverse osmosis, the RO booster pump raises water pressure.

Do you need a permeate pump?

Compared to several other pumps, a permeate pump doesn't require power to function. Rather, when the RO tank is almost full, it applies the hydraulic energy that would otherwise be spent to stop more water from draining. A permeate pump increases a RO system's efficiency by 80% and results in annual water savings measured in gallons.

Reverse osmosis systems are among the finest point-of-use household water treatment technologies, according to the Centers for Disease Control, however, they are ineffective when used alone. By lowering the volume of water going down the drain in comparison to the volume of clean water gathered in the RO storage tank, a permeate pump increases the efficiency of an RO system. The permeate pump allows the RO system to use less water for optimal performance.

Why an RO system needs a permeate pump

Systems for reverse osmosis produce water relatively slowly. They include a storage tank as a result, making RO water available when you need it. The tank is hydro-pneumatic, meaning that a diaphragm separates the two internal chambers (one for RO water and the other for air). The air in the tank compresses as the water fills it, creating energy that forces the water out of the tank and into your faucet. Water production is slowed by this energy's ability to cause resistance against the RO membrane. The system becomes less efficient when output slows down and the water to drain ratio rises.

To prevent production from being impacted by the rising pressure from the tank, the permeate pump forms a barrier between the tank and the RO membrane. The pump is powered by the water that is draining and is used to force RO water into the tank. This boosts productivity, keeps the drain-to-volume ratio low, and enables the membrane to function at its best for producing high-quality water.

Imagine attempting to enter a room, only to find someone pressing against the door from the opposite side. It can take a lot of work for you to succeed, but it will be much simpler if you have more allies. The permeate pump functions as an additional force to assist the membrane in overcoming the obstacle.

Benefits of a permeate pump

1. Increased efficiency

2. Higher water production

3. Reduced waste water

4. Improved water quality

5. Energy efficiency

6. Longer membrane life

7. Environmentally friendly

Saves water sent to the drain

For every gallon generated, a RO system throws three gallons of water down the drain. However, a permeate pump ensures that the amount of pure drinking water produced remains constant throughout, unlike wasted drain water.

Increase production

By reducing membrane pressure, a permeate pump speeds up the filling of the RO storage tank. Because of its increased efficiency, the pump also improves the volume of clean water that a RO membrane produces.

Requires no electricity

Rather than using power, filtration pumps generate energy from RO-reject water. The permeate water is forced into the reverse osmosis storage tank until you need it, using the energy they get from the wastewater that is meant for the drain.

How much does a permeate pump cost?

The cost of an Aquatec permeate pump can vary from $30 to $100 based on the daily volume of water generated. A permeate pump should only be purchased if your RO system is built to support it. If you're a new RO client, search for a system that is plumbed to accept a permeate pump or one that comes with one, such as the Neo-Pure deluxe system.

A permeate pump with or without ASO

An automatic cutoff (ASO) valve is typically used in reverse osmosis systems to halt water production prior to the storage tank filling up. Air pressure increases as the tank fills with water, forcing more water down the drain. The volume of water to be drained rises as the tank fills up.

When the water level in the storage tank reaches two-thirds of the incoming pressure, a permeate pump fitted with a shut-off valve prevents water from entering, lowering the water pressure at your faucet. When a permeate pump is used without a shut-off valve, water might fill the storage tank to full pressure. ASO devices and permeate pumps are not necessary; however, having both might help stop TDS creep.

How to install a permeate pump

In order to make it easier for you to know where to enter the tubing, permeate pumps are labeled with "brine in," "brine out," and "permeate in."

1. A mounting clip is screwed onto the manifold.
2. Put the pump into the top-mounted clips marked "permeate out" and "brine out."
3. Place the pump into the clip.
4. Reverse the RO system.
5. Take off the tubing from the membrane housing's permeate port.
6. Cut the tubing end that is not connected to the ASO valve.
7. Put fresh 22" tubing into the membrane housing's permeate port.
8. Tubing should be brought to the system's front.
9. Fit the tube into the port labeled "permeate out.".
10. Fit an elbow stem into the port designated for "permeate out.".
11. Put the 15" tube portion into the fitting.
12. Connect the ASO valve to the end of that tube.
13. Find the restrictor of flow.
14. 22" tubing should be inserted into the flow limiter.
15. Insert the tubing through the mounting clip's holes, facing the front of the system.
16. Attach an elbow fitting to the tubing's removal.
17. Fit the tubing into the port labeled "brine in".
18. The drain line is connected to the "brine out" port.

Some reverse osmosis permeate pump systems are simple to install, but not all of them are. The exception is small manifold RO systems with three or four tubing connections. The permeate pump restricts the direction of water flow, much like a check valve. Water must enter and exit the tank through the same line in the majority of manifold systems. In this kind of setup, you would have to remove the postfilter to install the pump.