Why Does My Reverse Osmosis System Make Noise?

On this page (9 sections)

1. Why does my reverse osmosis system make noise at all?
2. Is gurgling normal for a reverse osmosis system?
3. Why does my RO system click on and off?
4. Why is my reverse osmosis system making a grinding noise?
5. Why does my RO system hiss or whistle?
6. Why is my storage tank banging or knocking?
7. How can you quiet a noisy RO system?
8. When should you replace a part instead of adjusting it?
9. Which upgrade helps most with RO noise?

Most reverse osmosis noise is normal. Gurgling is drain water flushing away, and clicking is the shutoff valve or booster pump switching on and off.

Grinding, hissing or banging means something needs attention.

The first step is to identify the sound and where it comes from. Once you know whether it is water moving, a motor running or a pipe vibrating, the fix is usually simple.

This guide covers the common noises and what each one tells you about your system.

Why does my reverse osmosis system make noise at all?

An RO system makes noise because water is moving and parts are switching. A standard system has no motor, so most of its sound is water flowing, draining or refilling the storage tank.

Under-sink systems push water through several stages under pressure. When you open the faucet, water leaves the tank and the pressure drops, which triggers the auto shutoff valve to let more water in.

That flow is what you hear.

A system with a booster pump adds a small electric motor. The pump raises incoming pressure for the membrane, and its hum is the loudest part of a pumped system.

Normal RO sound is a soft gurgle, a trickle, or a brief click as valves move. Anything sharper is worth checking.

Is gurgling normal for a reverse osmosis system?

Yes, gurgling is normal. It is water flowing to the drain as the system flushes concentrate away and refills the storage tank after you use the faucet.

The membrane rejects a share of the incoming water, and that concentrate goes down the drain line. You hear it as a trickle or gurgle for a while after each draw.

This is also why reverse osmosis systems waste water, and the drain sound is part of that process.

The gurgle should stop once the tank is full. If the trickle never ends, the system is running continuously.

A stuck auto shutoff valve, a faulty pressure switch or a tank that will not hold pressure can all keep it flushing.

Check that the drain line has its air gap or saddle clamp in place and is not blocked. A partly blocked drain can change the sound to a gulp or a sputter.

Why does my RO system click on and off?

Clicking is the pressure switch and auto shutoff valve working. A full tank pushes pressure up and the system clicks off; using water drops it and the system clicks back on.

Short, spaced clicks are normal and usually tied to a draw of water. Rapid clicking that repeats every few seconds means the system cannot settle.

A leaky faucet, a tank that has lost air charge or a pressure switch set wrong can each cause it.

A booster pump kit uses a pressure switch to sense output line pressure. The Aquatec 8800 kit includes the PSW-340 switch and shuts the pump off when the storage tank reaches 40 to 50 psi.

If your pump clicks constantly, the tank or the shutoff valve is the usual cause.

Why is my reverse osmosis system making a grinding noise?

Grinding means the booster pump. A pump-free RO system has no motor, so a grinding sound points to the pump, its mount or something caught in the pump head.

Turn the water supply off and stop the system before you investigate. Check that the pump sits flat on its base plate and that the mounting screws are tight.

A loose pump vibrates against the cabinet and can sound like grinding.

The Aquatec 8800 pump comes on a heavy duty steel base plate with a damper, which reduces vibration. The kit also includes four reducer fittings and a 110V transformer.

Aquatec wet-tests every pump, so there can be water inside the pump head and temporary rubber plugs at the inlet and outlet when it arrives.

If the grinding continues with the pump mounted firmly, the pump itself may be worn. A pump is the part most likely to need replacement on a pumped system.

The Aquatec 8800 suits RO systems under 200 GPD.

Why does my RO system hiss or whistle?

A hiss or whistle means water is escaping under pressure, most often at a push-fit fitting or the tank valve. It can also be air leaving a newly installed system.

New systems often hiss for a short time as air works out of the filters. That fades within a few minutes.

A hiss that continues means a leak, even if you cannot see drips yet.

Tighten fittings and check the tubing at each connection. A tube pushed in only partway can whistle as water squeezes past.

Re-seat the tube by pushing it in firmly and pulling back gently to lock it.

The ESHIONG push-to-connect kit has a non-locking clip design and 1/4 inch fittings, so the tubing simply pushes in without tools. A properly seated tube should not hiss.

Why is my storage tank banging or knocking?

Banging or knocking is usually water hammer, a pressure shock in the pipes when a valve shuts quickly. An RO system's auto shutoff valve closes fast, and the sudden stop can send a knock through the plumbing.

Check for loose pipes behind the wall or under the sink. Secure any pipe that vibrates against a stud or cabinet.

A water hammer arrestor on the supply line can absorb the shock.

A tank with a failing air charge can also thump as water sloshes against the diaphragm. The iSpring T32M holds up to 3.2 gallons in a food grade butyl diaphragm chamber.

It ships pre-pressurized between 7 and 10 psi, and a tank at the right charge runs in longer, smoother cycles.

How can you quiet a noisy RO system?

Start by finding the source, then fix that part. Most noise comes from four places: the drain line, the booster pump, a loose fitting or the storage tank.

Listen with the cabinet door open while you draw a glass of water. Note whether the sound starts with the faucet, continues after it closes, or happens when no one is using water.

That timing narrows the cause.

Then check the simple things. Secure loose tubing with clips, set the pump on its damper base, and tighten any fitting that hisses.

Make sure the tank holds pressure and the drain line runs clear.

If your water pressure is low, the pump may run longer than it should. Our guide to low reverse osmosis water pressure explains the causes.

Fixing pressure problems often shortens run time and quietens the system.

When should you replace a part instead of adjusting it?

Replace a part when the noise returns after a proper adjustment. A pump that grinds after remounting is worn.

A tank that loses its charge again after re-pressurizing has a failed diaphragm.

A switch that clicks rapidly after the tank is charged is faulty.

Also replace any fitting that leaks after you re-seat the tube. A fitting that will not hold is a leak risk, not just a noise.

Keep the rest of the system in good order too. Change the filters on schedule, because a clogged prefilter can make the pump work harder and run louder.

In a small space where sound carries, a compact system suits better. Compare options in our guide to the best reverse osmosis system for an apartment before you buy new.

Which upgrade helps most with RO noise?

A correctly charged storage tank helps most, because it keeps the system running in long, quiet cycles instead of short bursts. A booster pump kit comes next for systems with weak incoming pressure.

The tank is the part that decides how often the system cycles. A tank that holds its air charge means fewer start and stop cycles, which means less clicking.

If your tank is old or waterlogged, replacing it can quiet the whole system.

A pump helps when low supply pressure makes the system run too long. The Aquatec 8800 raises input pressure from 30 to 40 psi to 60 to 80 psi for systems under 200 GPD.

Higher, steadier pressure means the membrane fills the tank faster and the pump runs less often.

A larger home kitchen system may already have these parts. See the best reverse osmosis system for home kitchens if you are choosing a new unit.

Either way, the goal is the same: steady pressure and long cycles, which is also the fix for most why does my reverse osmosis system make noise questions.

Start with the sound. If it is a gurgle or a click, your system is working as designed.

If it is a grind, hiss or bang, fix the pump, fitting or tank before it becomes a leak. When in doubt, shut off the supply valve and call a plumber.

Frequently asked questions

What does a grinding noise from an RO system mean?

Grinding almost always means the booster pump, since a standard system without a pump has no motor to grind. Turn the system off at the valve and check the pump mounting and fittings before running it again.

Can a full storage tank cause noise?

A tank that has lost its air charge can cause short cycling and clicking as pressure swings quickly. The iSpring T32M ships pre-pressurized between 7 and 10 psi, and a properly charged tank keeps the system running in longer, quieter cycles.

When should I call a plumber instead of fixing it myself?

Call a professional if you see water leaking from a fitting you cannot tighten, if the noise comes with a pressure drop you cannot trace, or if the sound is a banging pipe behind a wall. Mains water pressure and plumbing work are jobs for a licensed plumber.