my apec reverse osmosis system is making a humming noise, is that normal?

Diagnosis

A humming or vibrating noise in an APEC ROES-50 system is almost never a sign of mechanical failure, as the system is non-electric and contains no motors or pumps. Instead, this is a resonance issue caused by the high-pressure flow of wastewater. As the system rejects impurities, water is pushed through the black 1/4" drain tubing at a constant rate. If that tubing is loosely draped or touching a wooden cabinet wall, the high-frequency vibration of the water molecules and air pockets creates a "hum" that is amplified by the hollow space under your sink, acting like a sounding board.

You can confirm this is the cause by performing a "touch test." While the system is humming (especially during the tank-filling phase), gently press your finger against the black drain line at various points along its path. If the noise stops or changes pitch when you apply pressure to a specific spot, you have identified the vibration point. This typically occurs where the tubing makes contact with the side of the cabinet or where it enters the drain saddle clamp on your waste pipe.

How to Fix It

To eliminate the resonance, you must decouple the tubing from the cabinet surfaces and stabilize the line to dampen the vibrations. Follow these steps:

1. Locate the black 1/4" drain line starting from the RO membrane housing and following it to the drain saddle (the plastic clamp attached to your sink drain pipe).
2. Identify every point where the tubing is touching the cabinet wall, the bottom of the sink, or other plumbing pipes.
3. Use adhesive-backed plastic cable clips or heavy-duty zip ties to secure the tubing. Do not pull the ties so tight that they pinch or kink the tube, as this will restrict wastewater flow and increase pressure on the membrane, potentially shortening its lifespan.
4. Create a "buffer zone" by placing a small piece of adhesive foam weatherstripping or a rubber gasket between the tubing and the cabinet wall at the primary contact points.
5. Check the drain saddle clamp. Ensure the screw is tight enough to hold the tubing firmly against the waste pipe, but not so tight that it crushes the plastic tubing. If the saddle is vibrating against the metal pipe, wrap a single layer of electrical tape around the pipe before tightening the saddle.

If That Didn't Work

If the humming persists after securing the lines, consider these alternative causes:

• Air Trapped in the Membrane: If the system was recently installed or a filter was changed, air pockets can cause erratic flow and humming. Open the RO faucet and let it run for 5-10 minutes. If the tank is empty, allow the system to fully recharge (usually 2-4 hours) to purge all air from the housings.
• Automatic Shut-Off Valve (ASO) Chattering: The ASO valve controls the flow of water to the membrane. If the valve is failing or partially clogged, it can "chatter" as it tries to close, creating a rapid humming sound. This is common after 3-5 years of use. Replace the ASO valve (Part #APEC-ASO) to restore silent operation.
• Water Hammer Effect: If the hum occurs specifically when the system stops producing water, it may be a water hammer issue in your home's main plumbing. Installing a small water hammer arrestor on the cold water feed line leading into the RO system will absorb the pressure shock.
• High Feed Water Pressure: If your home's incoming water pressure exceeds 80 PSI, the flow through the ROES-50 can become turbulent. Install a pressure-reducing valve on your main line to bring the pressure down to the recommended 40-60 PSI range.

Heads Up

• Never kink the black drain line to stop the noise; restricting the waste flow will cause minerals to build up rapidly on the membrane, ruining the system.
• Check your drain saddle every six months. The plastic can degrade or loosen, which may lead to leaks or a return of the vibration noise.
• When replacing filters, always ensure the O-rings are lubricated with a food-grade silicone grease to prevent air leaks that contribute to noise.
• If you notice the humming is accompanied by a slow leak at the fittings, use a small piece of Teflon tape on the threaded connections, but never on the quick-connect push-fittings.