Reverse Osmosis Water Flow Slow? Here’s Why + How to Fix It!
Written by: Gene Fitzgerald // Last Updated: May 9, 2023
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Slow water flow can be a common complaint for those with reverse osmosis systems, but it is always good to be able to differentiate between a normal slow flow rate and a slow flow rate that indicates a problem.
Common causes of slow flow rates from a reverse osmosis system include sediment build-up, clogged filters and membranes, a worn-out storage tank, or problems with the system’s feed water pressure.
To figure out what your issue might be, read on!
Contents
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Key Takeaways
Here is what causes slow reverse osmosis water flow and what to do about it:
- Low feed water pressure – increase
- Low feed water temperature – increase
- Clogged RO membrane – replace
- Clogged pre or post-filters – replace
- Clogged or kinked tubing – remove
- Underpressurized storage tank – repressurize
- Ruptured tank bladder – replace
- Air inside RO system – release
- A closed valve – open
Why Is My Reverse Osmosis System Slow?
Why is my reverse osmosis system slow, you ask?
Slow water flow rates are pretty standard with reverse osmosis systems. In fact, they will have much slower flow rates compared to your regular kitchen faucet, which is normal.
But if your reverse osmosis system is running at an abnormally slow pace, it could be because of clogged filters, low water pressure, or insufficient cleaning and maintenance of the unit among other issues.
Thankfully, there are a few simple ways to troubleshoot a slow-flowing RO system; it might be an easier fix than you think!
Is Your RO Water Tank Empty?
Before pulling things apart and buying new parts, check your RO storage tank. It might just be empty! You should be able to tell by the weight if you lift it or by looking at the gauge on the side of your storage tank in case there is one. If the tank is empty, wait for it to refill before using the reverse osmosis faucet again.
If your tank is empty but not because you have used all the water before it has had a chance to refill, then you will need to check that water is actually getting into the tank.
How to Fix a Reverse Osmosis System Running Slow
If it isn’t a simple case of the storage tank being empty, then the next steps are to identify what could be causing a decrease in reverse osmosis water flow. Here are a few things to look out for.
Low Feed Water Pressure
A decrease in feed water pressure is a common cause of slow flow from an RO system. The feed water coming into your RO system should be around 60 psi; anything below 40 psi is inadequate for the unit to function correctly.
You can measure your home water pressure with a pressure gauge, and if it is low, you might need to consider increasing it or installing a booster pump.
Low Feed Water Temperature
Water temperature is another thing that may affect the flow rate of a reverse osmosis system. Water that is too cold will result in a reduced flow rate. This is because cold water is thicker than warm water, which means it moves more slowly.
The optimal temperature for feed water is 77° Fahrenheit. If your water is much colder than this, you may want to have the water lines close to a heat source to warm it a little before it moves through the system.
A Clogged RO Membrane Can Slow RO Water Flow
Another common issue that reduces the flow rate is a clogged RO membrane. If you have water high in total dissolved solids or one of your pre-filters isn’t working as it should, debris can accumulate on the reverse osmosis membrane, clogging the pores that allow the water through. If this is the case, the membrane will need to be replaced, as will the filters.
Besides, reverse osmosis membranes usually last for 2 to 5 years so if yours is well past that, it’s probably time for a replacement.
Clogged Pre/Post-Filters
Clogged pre-filters or post-filters could be another issue, especially if you haven’t been replacing them according to schedule. This is why maintenance is so essential! Debris blocking any pathway that the water needs to travel through the system will cause a decrease in the flow of the water from your RO faucet. If this is what you’re facing, the filters must be replaced.
Some Other Clog or Kink in Water Line That Disrupts Flow
The water lines in a reverse osmosis system aren’t as big as the regular pipes that plumb your home, they are smaller and more flexible. Therefore, they can be subject to kinking or bending, resulting in blockages.
Inspect your lines for any signs of kinking or bending that need to be straightened out, and any blockages in the lines can be cleaned with a pipe cleaner or other such instrument.
An Underpressurized RO Storage Tank
The correct pressure for your RO storage tank is between 6 and 8 psi when empty, and should be listed on the tank label as it may vary by manufacturer. If the storage tank pressure is too low, it means there is not enough pressure to push the water from the tank out through the RO faucet.
To check, you need to empty the storage tank of water, measure the psi, and adjust if needed.
Ruptured Tank Bladder
There is a possibility that the bladder inside the reverse osmosis tank has ruptured. If you have tried to repressurize the tank a couple of times, and it seems to be failing again after a day or so, it is likely due to a ruptured bladder.
You could also check by filling an 8 oz glass of water. If the flow rate drops immediately after this, then it is likely that your tank bladder is ruptured. There is no way to repair this, and you will need to purchase a new storage tank.
Air Inside Reverse Osmosis System
Sometimes, air can become trapped somewhere in the RO system, leading to a drop in flow. To troubleshoot, open the RO faucet and tilt the system back and forth while draining the water. This will loosen air pockets that may be trapped inside.
A Closed Valve
It seems obvious, but sometimes the small things are the things that you miss! Check the valves to the RO system; they may be closed.
How to Determine Water Flow Rate of an RO System
RO water does flow slower than municipal water from a regular faucet, so how do you know when slow becomes too slow? To determine the water flow rate of a reverse osmosis system, you should check your RO system’s GPD (gallon per day) rate as listed by the manufacturer and compare it with the actual flow rate you are getting. You can do this as follows:
- Turn the valve on the RO storage tank off.
- Turn on the RO faucet as far as it can go in the ‘on’ position.
- Run the faucet until it gets to a slow drip.
- Get a measuring cup and let water drip into it for 60 seconds.
- Measure the amount of water and multiply it by 1,440, then divide that number by 128.
- Your current number is the amount of water your system produces in 24 hours.
Now compare your GPD output to the value specified by the manufacturer. If it is within 50 to 75% of it, then all is good. Below 50% might indicate one of the underlying issues as discussed above.
You can also measure water pressure in your RO system with a pressure gauge right before the RO membrane. This will tell you exactly how much pressure is going to the membrane so that you can adjust it.
Is Slow Flow Normal?
This is a question new RO system owners often have because, yes, RO water has a slower flow than regular water from your household faucets, and it takes a little getting used to.
Considering a storage tank only holds a certain amount of water and fills slowly over an extended period, a slow flow rate means you won’t use excessive amounts all at once. The slow flow rate you are experiencing might be normal, so it is best to check the actual gallons per day produced if you have any concerns.
Further Reading:
How to Maintain/Increase Reverse Osmosis Water Pressure
If your flow rate within your reverse osmosis system is slow, or you simply want to maintain the adequate flow rate you already have, there are a few things you can do.
Maintain Your System According to Schedule
Changing your system filters regularly is really important to prevent filter and membrane fouling and clogging, which is one of the main culprits of a slow flow rate. Pre-filters must be replaced every 6 to 12 months, depending on your feed water conditions and level of use. Post-filters should last around 1-2 years, and reverse osmosis membranes should last 2 to 5 years.
Storage tank psi should be checked annually when the storage tank is empty. You may need a bicycle pump to repressurize it if it is low.
Cleaning and sanitizing your RO system should be done when you replace the filters once or twice yearly. If you don’t use your RO system often, drain it every few weeks and refill it to keep things working properly.
Pressure/Permeate Pumps
The addition of a pressure pump or a permeate pump can increase the flow rate of your RO system and help reduce the amount of wastewater produced. Win-win!
Add a Second Tank
Adding a second tank to your reverse osmosis setup may also help. The water pressure from an RO system is higher when the storage tank is full, so double the tanks means double the water power!
If you have any questions about reverse osmosis running slow please don’t hesitate to leave a comment below!
About the Author Gene Fitzgerald
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