What is a permeate pump in reverse osmosis water filters and how does it work?

What is a permeate pump in RO water filters and how does it work?

Hey, do you have a reverse osmosis water filter that isn’t properly filling up the storage tank? Or, is your RO filter drains water all the time?

Then, you have a solution for you. You have to use a permeate pump with your water filter. Now, what’s that?

In this article, we’ll be discussing everything you need to know about permeate pumps and how they can improve the efficiency of your RO water system.

Also, if we’ll see how installing a permeate pump can significantly reduce the amount of wastewater from your RO filter.

So, if you’re looking for answers to all these questions, stay with us. We’ll answer them one after the other.

Let’s go.

What is permeate water?

So, let’s start our discussion by defining what reverse osmosis is and what permeate is.

Reverse Osmosis is the process in which tap water goes through a selective membrane, and only the pure water molecules can pass through.

As a result, you get pure and clean water from a RO water purifier.  We have already mentioned that you will need a membrane for the Reverse Osmosis process.

When the tap water enters the membrane, it gets divided into two different species of water at the output.

  • The first one is clean and pure water, devoid of most of the pollutants. This one is called permeate water. Sometimes, we also call it the product water. 
  • The other species of water will contain most of the dissolved solids. This one has a variety of names. The prominent of those is RO reject water. Sometimes, we also call it Brine water.

So, in short, permeate water is the product water that we will be drinking, and the RO reject water will take the existing pollutants to the drain.

If you would like to know further about what reverse osmosis is, you should visit our article here. Here we’ve explained how Reverse osmosis selectively filters water to purify it. Check it out.

What is a permeate pump?

  • In general, a pump is a device that we use to increase the pressure or flow rate of a  fluid. The fluid can be in liquid or gaseous form.

We use a variety of pumps in our everyday life. For example, in skyscrapers, there are centrifugal pumps that would lift water at various heights of the building. 

We even use pumps in our houses as well. The supply water that we get may not pack sufficient pressure to reach every point of our home. That’s why we need pumps.

The permeate pump falls into the category of hydraulic pumps that we use with RO water filters. There are two types of RO pumps out there.

  • RO booster pump
  • Permeate pump 

The RO booster pump is used to improve input water pressure into the RO water filters. The increased pressure enhances the purifying ability of RO filters.

On the other hand, permeate pumps would improve the flow rate at the output of the RO chamber. So, what’s a permeate pump?

A permeate pump is a hydraulic device that increases the efficiency of a RO water purifier by discharging the purified water or permeate water fast. 

Now, let’s first see what is inside a permeate pump. Also, if you’d like to know more about RO booster pumps, you should check out our recent article here.

What are the components of a permeate pump?

Now, let’s talk about the components of a permeate pump. As we’ve already discussed, the permeate pump is a type of hydraulic device.

It consists of two inlets, one for the brine water and the other for the product water. The same goes for the two outlets as well.

Inside the device, cranks and pistons are set up to increase the flow rate of the purified water.

  • Brine water or RO reject water from the reverse osmosis membrane enters the brine or RO reject inlet point of the permeate pump. Then, it leaves through the brine outlet point.
  • On the other hand, the product water enters the permeate pump and then leaves through the outlet point of the permeate pump.

The pump has a setting with cranks and pistons. The RO reject water pressure will move the pump that will rotate the crank and the piston.

The movement of the piston creates suction and takes in permeate water. Then, it will push the piston back and push the permeate water through the output.

So, you see cranks and pistons move in a reciprocating manner to improve the water pressure of the product water.

How does a permeate pump work?

As you’ve seen in the previous section, the permeate pump uses cranks and pistons to increase the flow rate and water pressure of the permeate pump.

Now, let’s discuss how that happens. You already know that input water in the semipermeable membrane of the reverse osmosis water filters divides into two types at the output.

  • The purified water or the permeate water
  • The RO reject water or the brine water

Most of the RO water purifiers will take in 10 gallons of tap water to produce only one gallon of purified water.

That means the rest of the water is referred to as the RO reject water that goes to the drain generally. So, you see, as the quantity of rejected water is higher, it will have a larger pressure head.

  • This higher pressure and flow rate of the RO reject water helps turn the pump. As a result, the crank rotates, and the piston goes back to create a suction pressure.
  • As a result, more purified water can enter the permeate pump. The piston then pushes back the stored energy into the purified water and diverts it to the outlet.

In this fashion, the permeate pump uses the kinetic energy from the RO reject water and distributes that into the permeate water to increase water pressure and flow rate.

Why do you need to use a permeate pump?

Now, let’s find out the reasons for having a permeate pump with your reverse osmosis water filters.

There is more than one reason to do this. So, let’s take a look at the reasons behind installing a permeate pump.

  • Permeate pump will fill up your RO storage tank at its maximum capacity.
  • It will fill up the tank within a short time and reduce the amount of wastewater.
  • Permeate pumps will also improve the overall efficiency of your RO filtration system.

Now, let’s elaborate on these points.

Permeate pump fills up your RO storage tank at its maximum capacity

If you’re familiar with RO water filters, you already know that all the RO purifiers come with a reserve tank of their own.

  • The storage tanks are vital for the proper operation of the RO purifiers. As the purification process takes time inside the RO chamber, the tank holds the purified water for later usage.

If you’re eager to know what are the components of a conventional RO water filter, you should take a look at our recent article here.

So, in short, the RO storage tank would hold the purified water, and as soon as you open the faucet, the water will get out at a moderate flow rate.

Now, if you look at the structure of a storage tank, you will find that there are two chambers. One will hold the purified water, whereas the other one will hold air to serve pneumatic energy.

  • In most cases, most RO tanks can store 3-5 gallons of purified water at a time. The quantity varies from one brand of filter to the other.

Now, if the input water pressure at your system is low, the tank will not fill up to its maximum capacity. 

  • For example, if the water pressure is 40 PSI, any APEC water filter tank would store 1.9 gallons of water while the amount would be 3.1 gallons if the pressure reaches 70 PSI.

So, if your system is lacking enough water pressure, you need to install a permeate pump. It will improve the pressure of the purified water, and in turn, the tank will fill up at its maximum capacity.

If you would like to take a look at how the storage tank works, you should check out our recent article here.

Permeate pump will fill up the reserve tank fast 

Now, let’s talk about another aspect of the RO water tank. As you’ve seen in the previous section, the RO water filter uses tanks to store the water and serve you during your need.

One thing you need to know is that these RO tanks generally require a certain amount of time to fill up the tank. 

  • In most cases, the RO tanks will require from 1.5 to 3 hours to fill up the tank regardless of their capacity. But, as you’ve seen earlier, more time may be required if water pressure is low.

You can guess how permeate pumps can help in these prospects. They will raise the water pressure, and subsequently, the flow rate will rise as well.

  • Therefore, now, it will take a shorter period to fill up your reserve tank. You will find that after installing a permeate pump, your storage tank will fill up within 45 minutes to 1 hour.

So, in short, a permeate pump cuts through the time required to fill up your reserve tank while also filling it up properly.

Permeate pumps improve the overall efficiency of your RO filtration system

Now, let’s talk about efficiency.  We’ve discussed earlier, the permeate pumps will kinetic energy from the RO reject water and serve it to the permeate water.

As water passes through the RO chamber, it will lose a significant amount of pressure, and the flow rate will go down as well.

  • As a result, the permeate water might take a long time to reach the tank, and it will not fill up to its capacity. Meanwhile, the purifier will continue to take in more water.

Therefore, it will waste more and more water. That’s where the permeate pump comes in. It will increase the flow rate of the purified water, and the tank will fill up fast.

  • In turn, it will make sure there is no clogging of permeate water at the RO output point. Also, the auto shut off valve will automatically turn off the system as the tank fills up.

So, you see, the permeate pump shortens the time required to replenish the tank and reduces the amount of wastewater in your RO system.

In this way, the permeate pumps can improve your RO water filtration system’s overall efficiency.

Concluding remarks

Throughout this article, we’ve discussed everything you need to know about permeate pumps and their roles in RO filtration systems.

We’ve shown you what the components of a permeate pump are, how it works, and how it can help improve the efficiency of your reverse osmosis water filtration system.

  • If you’re facing problems like your water storage tank not filling up properly, you should think about installing a permeate pump in parallel with your RO system.

If you still have any questions about permeate pumps, feel free to leave those in the comment section. Also, don’t forget to share it with your friends.

1 thought on “What is a permeate pump in RO water filters and how does it work?”

  1. Very well written with options (links) that give the reader options related to detail of the RO system components. There is a lot of information here and I skimmed the article but will go back to details. I will also go to the various links.
    I find that the little knowledge I had is now increased.
    I know how the tank works with the rubber bladder inside but will read it to get more information. Thank you for the great article.

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