the black drain line from my apec roes-50 keeps popping out of the saddle under the sink.

Diagnosis

The issue where the black 1/4" drain line pops out of the ROES-50 drain saddle is almost always caused by an incomplete seat within the quick-connect collet. In these push-to-connect fittings, a small metal gripping ring (the collet) must clamp down tightly on the outer diameter of the polyethylene tubing. If the tube is only inserted 1/8" or 1/4" of the way, it rests on the edge of the internal O-ring rather than passing through it, creating a weak connection that fails under the slight pressure fluctuations of the RO system's waste cycle.

Furthermore, this often happens because the tubing end has become "mushroomed" or scarred from previous failed attempts to push it in. If the end of the tube is slanted or jagged, it cannot slide past the internal O-ring seal, preventing the gripping teeth from locking onto a secure section of the pipe. You can confirm this by pulling the tube out and checking if the end is flared or if there are deep gouges in the plastic; if the tube slides out with zero resistance, the collet is either damaged or the tube was never fully seated.

How to Fix It

To permanently secure the drain line to the saddle, follow these precise steps to ensure a mechanical lock:

1. Shut off the cold water supply valve to the RO system to prevent any accidental leaks while you are manipulating the lines.
2. Depress the small circular collar (the collet) on the drain saddle and pull the black 1/4" tubing completely out.
3. Use a sharp utility knife or a dedicated tubing cutter to make a perfectly square, 90-degree cut across the end of the black tubing. Do not use scissors, as they often crush the tube into an oval shape, which prevents a proper seal.
4. Inspect the end of the tube to ensure it is smooth and circular. If there are any scratches or "mushrooming" from previous attempts, cut off an additional 1/2 inch of tubing.
5. Push the tubing firmly and straight into the saddle port. You will feel an initial resistance as it hits the O-ring; you must apply a strong, steady force to push it past that seal.
6. Continue pushing until the tubing bottoms out. For the ROES-50 saddle, the tube should be inserted approximately 3/4 of an inch deep.
7. Gently pull back on the tubing with moderate force to verify it is locked. If it slides out, repeat the cutting process and re-insert.

If That Didn't Work

• Replace the Drain Saddle: If the tubing is cut square and pushed in fully but still pops out, the internal metal gripping ring (collet) may have lost its tension or become deformed. Replace the saddle assembly entirely to ensure the locking mechanism is functional.
• Check for Kinks: Ensure the black tubing is not under extreme tension or pulling at a sharp angle. If the tube is stretched too tight across the under-sink area, the constant lateral tension will eventually pull the tube out of the fitting. Create a small loop of "slack" tubing near the saddle to neutralize this tension.
• Inspect for Debris: Use a flashlight to look inside the saddle port. If a small piece of plastic from a previous tube break is lodged inside, the new tube cannot seat deeply enough to be gripped by the collet. Use a thin needle or compressed air to clear the port.
• Verify Tubing Diameter: Ensure you are using genuine 1/4" LLDPE tubing. If a non-standard or thinner-walled tube was substituted during a previous repair, the collet will not have enough material to grip, causing the line to slip.

Heads Up

• Never use Teflon tape or pipe sealant on the outside of the tubing before inserting it into a quick-connect fitting; this increases the diameter and prevents the collet from gripping the plastic.
• Avoid bending the black drain line too sharply near the saddle; a bend radius of less than 2 inches can put outward pressure on the fitting, compromising the seal.
• Periodically check the drain saddle for "creep," where the tube slowly backs out over several months due to vibration from the water lines.
• Ensure the saddle is clamped tightly to the drain pipe; if the saddle itself is loose or wobbling, it will transmit that movement to the tubing and eventually shake the line loose.