Reverse Osmosis System Making Hissing Sound? Here’s Why + Fixes!
Written by: Gene Fitzgerald // Last Updated: Jun 1, 2023
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You might need some time to get used to the way a reverse osmosis system works if you recently installed one for the first time.
More specifically, you might need to get adjusted to the system making various unusual noises from time to time.
Hissing is one of those noises. Some amount of hissing is to be expected, but if it’s persistent and very loud, you might need to investigate for potential problems…
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Key Takeaways
- Some amount of hissing is to be expected from a reverse osmosis system while it processes water. A new system or recent filter replacement can also cause hissing that should subside soon.
- However, if the sound is too loud or persistent, it could indicate a problem. Loud hissing from a flow restrictor could indicate excessive feed water pressure (adjust). An air gap faucet might hiss if there is an obstruction in its drain line (clean) or cracked tubing (replace). A shifted drain line can also result in hissing noise (realign).
Why Is My Reverse Osmosis System Making a Hissing Noise, and How Can I Fix It?
Your reverse osmosis system might be making a hissing noise for various reasons. One of the most common ones is the flow restrictor malfunctioning. Or you might have a defective drain connection.
A Hissing Flow Restrictor
Hearing some amount of hissing from the flow restrictor can be completely normal. The sound might be more pronounced at high levels of feed water pressure. If you want to reduce that noise, you should install a flow reducer before your reverse osmosis unit.
A Hissing Air Gap Faucet
Whenever a reverse osmosis system is processing and water is making its way down the drain, you’ll hear some amount of hissing noise. That’s coming from the air gap, which normally works to prevent the system from drawing in any dirty water out of the drain.
You should check for any deposits that might have built up in your drain line. Those could cause hissing noises that resemble whistling. Keep in mind that if your system is brand new, that’s most likely not the cause as these buildups take time to develop.
Under no circumstances should you ever attempt to bypass the air gap feature. This could make your water hazardous to drink.
Cracked Tubing
Furthermore, investigate your drain tubing to see if there are any obvious cracks between the air gap and the drain saddle. Cracks could introduce additional air into the system, leading to hissing noises. A very tiny crack is enough to cause significant noise, so be vigilant in your investigation.
Further Reading:
A Shifted Drain Line
You have to ensure that your drain line and drain saddle are centered properly. A shifted drain line could cause a hissing sound. It should be very easy to do a visual inspection to verify if that’s the case. If it is, you just have to realign the drain line and run the system for some time to see if the problem returns.
Normal vs Abnormal RO Hissing Sounds
Keep in mind that it’s completely normal to hear some amount of hissing when you’re running a reverse osmosis system for the first time or when you replace filters. The system goes through some initial adjustments until it settles in, and there might be air trapped along your pipes that has to be removed first.
Also, an air gap faucet will draw in some air whenever water is being purified.
If the hissing persists after a few days, that probably indicates an actual problem.
If you have any questions about reverse osmosis hissing sound please don’t hesitate to leave a comment below!
About the Author Gene Fitzgerald
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