What Is An Ro Flow Restrictor And When To Change?

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Nowadays, water purifiers can be seen as a requirement in almost every household. According to WHO, about 71% of people utilized safely maintained drinking water assistance worldwide in 2015.

With special purification techniques, RO water purifiers have made a massive name for themselves in the market. PureIt and Aquagurad are considered some of the Best RO Water Purifiers In India.

Flow restrictor plays a crucial part in these RO water purifiers. It is required in almost all RO or reverses osmosis systems.

Flow restrictors are a significant element in water purifiers and they help in maintaining the purifier’s recovery ratio. Most people often struggle to understand what flow restrictors are and how they work.

Therefore, in this article, I will explain flow restrictor, why it is essential, and when it should be changed or replaced.


What Is A Flow Restrictor?

RO Flow Restrictor

A flow restrictor is a tool that helps to restrict the movement or flow of RO rejected water. This flow restrictor assists in managing the high-pressure level obtained under the RO membrane by producing back pressure on the membrane.

Also, it helps in managing the recovery ratio of the water purifier. A flow restrictor was designed to be utilized in the residential RO systems.

Flow restrictors were made so they could be used in reverse osmosis systems. Its ability to restrict the water flow on the drain line helps to keep the membrane in a pressurized state.

The size of the flow restrictor must be compatible or matched with the membrane system based on the flow.

The water can begin to flow in the booster pump if the flow restrictor isn’t installed.

You might witness the water flow moving in an unopposed way through the drain vent of the RO membrane.

This could create an expansion of low pressure and might even cause wastage of water. Another thing about the RO membrane is that it couldn’t work precisely if the pressure wasn’t high.


When Should You Change A Flow Restrictor?

Your flow restrictor should be changed when you are changing your RO membrane. This way, you can make sure you are getting the best results, and this will help run your system efficiently.

The flow controls indicate the flow rate in millilitres/minutes. The restrictor installed in the water purification unit should adequately match the production rate of the membrane.

Just like RO filters and membranes, flow restrictors can get choked due to scale build-up. Also, when an RO membrane is changed or replaced, it can accommodate a different capacity, making it crucial to replace the flow restrictor according to the capacity.

Therefore, you should replace both the RO membrane and flow restrictor together.


How To Get A Correct Flow Restrictor?

Flow restrictor contains ratings that indicate the flow rate in ml/min. The membrane capacity can be described as GPD (Gallons Per Day).

One gallon is equal to 3.78 litres. The value of the restrictor has to be around four times the capacity of the membrane.

Therefore, to find the correct flow restrictor, you have to change the capacity value of a flow restrictor into Gallons per day.

To determine this, you have to multiply the capacity of the flow restrictor by 0.38 then this will get converted into GPD. For instance, if the flow resistor is about 800 ml, then in order to turn it into GDP, you have to multiply it by 0.38.

Then you will get a membrane capacity of 304 GDP.

You need to be assured the flow rate is around 4 times the capacity of the membrane.

Accordingly, you have to divide it by 4, which will give you 76 GDP. 

It will indicate that if the RO membrane is 76 GDP, then an 800ml flow restrictor could be perfect.


Why Is It Essential For The Flow Restrictor And RO Membrane To Match?

To maintain a proper balance amid the water wastage and the quality of purification, you should coordinate the capacity of the flow restrictor and the membrane.

If RO membrane and flow restrictor capacity aren’t matched, it can generate extensive wastage of water and might even reduce the RO membrane’s life.

Suppose you are using a flow restrictor of low capacity for a membrane of high capacity. In that case, it can occur in early choking of RO membrane, enhance the TDS value of purified water, and even decrease the membrane life.

While, if you use a flow restrictor of high capacity for a membrane of low capacity, then it might result in lower pressure inside the RO membrane and cause high wastage of water.

A low pressure present in the RO membrane can even provide an adverse effect on the purification quality.



1. How will I know if the RO flow restrictor is becoming bad? 

If you witness either no water or too much water flowing in the drain, then it might be an indication of your RO flow restrictor getting bad. If the restrictor completely stops and no water can drain, then the RO unit is repressed and the water quality will start getting bad.


2. Where should I install the flow restrictor in an RO? 

A flow restrictor is inserted in the 1/4 drain line tubing. The method to install a flow restrictor is very easy and straightforward, and you have to push the 1/4 poly tube gently in the quick connecting fittings, which are located at the ends of the flow restrictor in the inlet and outlets. Then your RO flow restrictor will be installed.


You May Also Like To Read:

What Is RO Water?

Water Filter Vs. Water Purifier: What Is The Difference?

Water Purifier Buying Guide



Flow restrictors are highly crucial for restricting the flow of RO rejected water. Nowadays with such a high number of bacteria, viruses, we have to be extra careful regarding everything especially with the water we drink.

Therefore, we have mentioned almost everything a flow restrictor, why it is necessary, its correct size, and when to replace it.

If you face any doubts about the flow restrictor, then tell us in the comments.

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