Flow Restrictor 300 for RO Systems

The size of the flow restrictor you need for your reverse osmosis (RO) system depends on the membrane capacity (gallons per day or GPD). The flow restrictor must match the wastewater flow rate required for proper operation.

Here’s a general guide for flow restrictor sizing:

How to Choose the Right Flow Restrictor:

1. Find Your RO Membrane GPD Rating – It’s usually labeled on the membrane or in your system manual.
2. Match the Flow Restrictor to the Membrane – The restrictor should allow a 4:1 wastewater-to-purified water ratio.
3. Replace If Upgrading Membrane – If you increase your RO membrane capacity, you must upgrade your flow restrictor.

Types of Flow Restrictors:

• Capillary Tube – Inserted into the drain line, cut to adjust the flow.
• Inline Flow Restrictor – A small component installed in the drain tube.
• Combination Check Valve & Flow Restrictor – Found in some systems, serving dual purposes.

A flow restrictor in a reverse osmosis (RO) system is a small component installed in the drain line that controls the flow of wastewater going to the drain. It ensures the proper pressure is maintained across the RO membrane, allowing effective filtration.

Why is a Flow Restrictor Important?

1. Maintains Proper Pressure: RO membranes need sufficient pressure to push water through and separate contaminants.
2. Controls Wastewater Ratio: It regulates the waste-to-pure water ratio, typically 4:1 (4 parts waste, 1 part purified water).
3. Prevents Excess Water Waste: Without a flow restrictor, too much water would go to waste, reducing system efficiency.
4. Protects the RO Membrane: Too little pressure could damage the membrane or reduce its lifespan.

How It Works

• When water enters the RO membrane, the purified water (permeate) goes to the storage tank, while the rejected contaminants (wastewater) go to the drain.
• The flow restrictor controls the amount of wastewater, creating back pressure on the membrane to enhance the filtration process.

Types of Flow Restrictors

1. Capillary Tube: A thin tube inserted into the drain line, cut to a specific length based on the membrane size.
2. Inline Flow Restrictor: A small plastic device with a pre-set flow rate, installed in the drain tubing.
3. Combination Check Valve + Flow Restrictor: Some systems combine both functions into one unit.

When to Replace a Flow Restrictor?

• When upgrading the RO membrane (higher GPD requires a larger flow restrictor).
• If you notice excessive wastewater (means the restrictor is too large or faulty).
• If the membrane is not performing well (low pressure might indicate an undersized restrictor).

How to Choose a Flow Restrictor for Your RO System

Choosing the right flow restrictor is crucial for the efficiency and longevity of your reverse osmosis (RO) system. Follow these steps:

1️⃣ Identify Your RO Membrane Capacity (GPD)

The flow restrictor must match the gallons per day (GPD) rating of your RO membrane. This is usually labeled on the membrane itself.

2️⃣ Select the Correct Flow Restrictor

Each RO membrane size requires a corresponding flow restrictor to maintain the correct waste-to-pure water ratio (typically 4:1).

💡 Example: If you have a 100 GPD RO membrane, you need a 550 mL/min flow restrictor.

3️⃣ Choose the Right Type of Flow Restrictor

• Capillary Tube (Inserted inside the drain tubing, requires cutting to adjust flow)
• Inline Flow Restrictor (Pre-set, easy to install in the drain line)
• Combo Check Valve + Flow Restrictor (Common in some RO systems)

4️⃣ Replace the Flow Restrictor When:

✔ Upgrading your RO membrane to a different GPD
✔ Noticing excessive wastewater going to the drain
✔ Experiencing low pressure due to an undersized restrictor