Reasons Why Your Reverse Osmosis System Is Slow – And How To Fix It

Many Americans use reverse osmosis water filtration systems as a great way to obtain clean water for their households. However, without regular maintenance, an RO water system can become slow overtime.

A reverse osmosis system is typically slow due to a clogged RO membrane, low water pressure or a ruptured tank bladder. Other reasons include air in the system, low water temperature, kinks in the water line, clogged filters or an empty water storage tank.

This post will take you through why a reverse osmosis system can be slow and provide step-by-step instructions on how to solve each problem.

Why is my reverse osmosis so slow?

There are various reasons that may make a reverse osmosis system slow. These issues can be system-related, plumbing-related, or maintenance-related. An RO system without regular maintenance is almost guaranteed to experience a slow flow rate issue at some point.

Before going into details about the reasons behind an RO being slow, let’s first look at how you can analyze your RO system’s water flow rate.

How to Analyze Your Reverse Osmosis System’s Water Flow Rate

• Confirm that the water supply is turned on.
• Then, before it enters your reverse osmosis system, check the water pressure at any point in the incoming water line for a significant pressure difference.
• Do you detect any changes? Because if the water supply is good, the issue is most likely related to a reverse osmosis system breakdown.
• If you notice reduced water flow and low pressure, turn off the RO water system and examine the valve
• Examine the RO system carefully, and use the solutions provided below to hopefully fix your RO and have your water flow back up to speed.

Always remember to consult your brand’s user manual handbook for details specific to your system model.

8 Solutions for a slow RO system

1. Clogged RO Membrane.

A clogged RO Membrane is the most common cause of a slow reverse osmosis system.

The RO membrane usually becomes clogged after a period of use (typically around 6 months). They often become clogged due to the accumulation of hard water mineral content, such as calcium and magnesium, how acidic or alkaline the water is, or simply from the dirt, contaminants and sediments in your water. 

The RO membrane is delicate and can become blocked quickly. Because there is some variation between membranes, it’s best to replace it at the manufacturer’s recommended interval for your specific system.

In general however, RO membranes can last as little as 6 months in hard water areas, while in areas with soft water they may last up to 3 years.

If you live in an area with hard water (see the table below) then you will need to do more regular maintenance on your RO than is often advised by the manufacturer.

State	Water hardness category
Arizona	Very hard
Colorado	Very hard
California	Moderately hard to very hard
Kansas	Very hard
Montana	Very hard
New Mexico	Hard to very hard
Oklahoma	Hard to very hard
Texas	Hard to very hard
Utah	Very hard
Wyoming	Very hard

RO membranes that are not cleaned or replaced regularly will not only become dirty over time, but gradually cause small blockages and ultimately result in a slow water flow rate.

In case of mold infestation or damage, you will also need to replace the membrane sooner rather than later.

If your RO membrane is becoming clogged or damaged quickly because of hard water, you can consider investing in a water softener to improve the lifespan of your RO system and its filters and membrane.

Solution

Replace the RO membrane.

2. Ruptured RO tank bladder.

A ruptured RO tank bladder is another reason your RO is slow. Most RO systems come with an internal or external water tank. Although, not all have a tankless design.

These water tanks are pressurized and RO water is dispensed by sending water out by the tank’s air bladder. However, an RO tank bladder can rupture due to improper maintenance.

If the bladder ruptures, the tank will leak air and won’t be able to build up enough pressure to pump the water out, making it slow. 

Diagnosis for ruptured RO tank bladder.

• Leaking RO tank
• The water at the faucet is often salty or foul tasting
• Drain all of the water from the tank by opening the faucet.
  • Locate the tank and pull it up.
  • The bladder has ruptured if the tank feels heavy and full, but you can’t draw water out of the faucet.

Solutions to a ruptured RO tank bladder.

• Inspect the system to determine the problem.
• Replace the storage tank (see below).

How to replace an RO system storage water tank.

• Before replacement, determine the tubing size going from the tank to the filter and then to the faucet and the water tank size you need.
• To remove the water tank, shut off the flow system to the RO system and the tank.
• Disconnect the tubing from the tank by pulling it away.
• Unwrap the new tank and connect the fitting to it. You can use Teflon tape to ensure it fits tightly.
• Then, attach the tubing to the tank and the reverse osmosis system.

3. Pressure in the tank is low.

Another reason why a reverse osmosis could be slow is low water tank pressure. The water flow rate to the faucet will be impacted if your RO storage tank has low pressure.

Usually, without any water in the tank, RO tanks should have a tank pressure of 7-8 psi (Pounds per Square Inch) or that specified by the brand’s manufacturer.

• For instance, the Waterdrop RO recommends a water pressure between 14.5 PSI and 87 PSI.

Low water tank pressure can simply be a result of water pressure changes in household plumbing, or from the supply.

A minimum of 40 psi or more in the plumbing is required for an RO system to function correctly.

If your faucet has low water pressure, double-check the rest of your house’s faucets. If all faucets appear to have low water pressure, your local water utility may be experiencing reduced water pressure, which is temporary.

Low water pressure can be caused by a variety of factors, including mechanical challenges.

• For example, if your water supply is undergoing maintenance, the water pressure may briefly drop, affecting how your RO system functions during that time. Your RO system will unfortunately be slow until the problem is resolved.

How to check for RO system water pressure.

• Locate the shredder valve.
• Remove the whole contents of the water in the tank.
• To determine the pressure in the tank, use a pressure gauge.
• If the pressure is low, use a pump to add air until that which the user manual guidebook specifies. 
• Add a modest amount of air at a time, as too much pressure can cause the air bladder to rupture.

Solutions to low water pressure from the water supply source.

• If you are sure the low water pressure is due to an ongoing maintenance, then wait until the maintenance is complete.
• Call your local water utility company to file your complaint if it takes more time than expected.
• Invest in a pressure regulator.
• Purchase a booster pump to sufficiently increase the pressure if the problem is ongoing.

4. Low water temperature.

Reverse osmosis systems can also be slow due to low water temperature. This Is common during the winter months.

The flow rate will fluctuate as the water temperature changes. Water thickens as it grows colder, and the flow rate across a reverse osmosis membrane drops. On the other hand, as the water warms, it becomes thinner, increasing the flow rate across the membrane. 

The rate at which feedwater is delivered to the membrane element is known as feed flow. The lower feed temperature is always to blame for a slow in water on reverse osmosis systems during cold weather days.

Solutions

• You can use a temperature correction chart to calculate the system’s temperature-corrected production if you feel the feedwater temperature is the cause of production loss.
• To normalize system performance, you can use performance normalization software (if applicable to your unit).

Note: Do not use water from your water heater to raise the temperature of the water because of the lower feed temperature. RO membranes can’t withstand water temperatures above one hundred degrees Fahrenheit. Hot water will damage the membrane and RO system.

5. Kinked Water Line.

Kinks in the water line can result in slow reverse osmosis flow. Although uncommon, it is one of the reasons reverse osmosis might be very slow. The water flow rate will significantly decrease if your water line has a kink.

Kinks can also lead to cracks or leaks in the system and hence require immediate maintenance. 

Solutions:

• If the kink is not too sharp or severe and there are no visible cracks or leaks, you may consider straightening it.
• Consider using anti-kink or kink-free hose pipes or tubings. The labels used to identify them in hardware shops are anti-kink, kink-free, or non-kink tubing.
• Check that your RO system’s water supply line valve is fully open.

6. Empty RO water tank.

An empty water tank is a fairly obvious, but often overlooked reason for a slow reverse osmosis system. When water is filtered, and all the contaminants removed from the water, the water flows to the water storage tank until it will be used.

However, your RO tank will always be empty if the water consumption rate exceeds the rate of water produced by the RO system. The pressure in the water tank will reduce if the water level decreases.

If you do not give it enough time to fill up before making your way to the faucet to get a glass of water, the flow will be slow. This is nothing to worry about unless there are other underlying reasons, such as a clogged RO membrane or clogged filters.

Solutions:

• Allow time for the reverse osmosis tank to fill. It should take around 3 hours.
• Check the state of the filters because clogged filters are one of the reasons the water flow may be slow.
• When last did you replace your RO membrane? Double-check if it is clogged and requires replacement.

If this is a constant problem for you, you can consider investing in a tankless design RO system, or an RO with a better waste water-to-treated water ratio.

7. Clogged Filters.

One main and common reason why a reverse osmosis system is low is clogged filters. Reverse osmosis systems come with filters that become clogged after a period of use because of the sediment and contaminant particulate matter in your water.

Once the filters become clogged, you should replace them immediately.

If you don’t do it on time, the system can start experiencing some problems, which is usually a slow water flow rate.

Fortunately, most reverse osmosis systems include a filter replacement reminder. Please replace the filter according to the filter life indicator reminder.

There is no specific time for replacing filters, the filter life varies depending on the quality of the source water and the amount of water used.

Filters that are not changed regularly might become clogged with trapped pollutants, preventing the filter from functioning correctly.

Solutions:

• Consult your user manual on when you are supposed to be replacing your filters.
• Replace the filters immediately after your RO system filter replacement indicator illuminates.

8. Air in RO water system. 

Air in the RO water system is another reason why your RO is so slow. This can happen during the replacement of filters or during repairs. For example, air can enter the reverse osmosis system when a filter is replaced, resulting in slow filtration and low pressure.

Solutions:

• Make sure your faucet’s air gap isn’t clogged.
• Check the air gap using a flashlight to determine if water is leaking out. 
• Turn off your system and, if necessary, remove the faucet head to clear any clogs.
• If you just installed your RO system, open the faucet and let all of the water go. This will completely empty the tank and remove any remaining air.

How long does it take for a reverse osmosis to fill?

How long it takes for reverse osmosis to fill depends on the type of RO system you have, water pressure, water temperature, and the state of the filters and the system. An RO system that is in good condition can take approximately 2 to 3 hours to fill.

However, if the reverse osmosis has technical or maintenance issues, it might take longer to fill the storage tank.

How can I speed up my reverse osmosis?

To speed up reverse osmosis, buy an electric booster pump, add a water pressure gauge, install a whole house sediment filter, and a secondary water tank, and replace filters more often and as required.  Cleaning water tanks, investing in water softeners, and installing a flow monitor can also assist speed up RO.