My Moen Pop-Up Drain Is Leaking

Moen faucets are commonly used in bathrooms in North America. The company has been in business since the early 20th century, pioneering a faucet with a single handle to control both the hot and cold water. Most Moen bathroom faucets come with a pop-up drain. A lift rod mounted behind the spout on the faucet controls the stopper in the bottom of the sink, enabling you to fill or drain the sink without getting your hands wet. Since there are several moving parts involved, a pop-up drain may begin to leak over time.

Drain Flange

The drain flange is the circular part you see in the bottom of the sink basin. The flange extends below the underside of the sink and is sealed with plumber’s putty to the sink mounting surface. The underside of the flange is threaded to accept the pop-up drain tail piece. If water is leaking under the sink, try tightening the large retaining nut on the underside of the sink. If this does not work, you may need to remove the flange and reseal it with plumber’s putty.

Ball Rod

The ball rod connects the lift rod -- the part you see on top of the sink behind the faucet -- to the bottom of the stopper. This piece consists of a metal rod with a plastic ball attached to one end. The ball is sealed with gaskets on either side where the rod enters the tail piece of the drain. If the ball is worn or the gaskets are faulty, water could leak under the sink. Replacing the ball rod and the two gaskets should complete the repair.

Tail Piece

The tail piece connects the underside of the flange to your home’s waste pipe system. Tightening the connections on either side of the tail piece may put a stop to any leaks in this area. The tail piece also accepts the ball rod that controls the up and down motion of the stopper. Since the tail piece on some Moen pop-up drain assemblies may be made from plastic, a crack or break in the tail piece may cause a leak. To replace a tail piece, unscrew the nut that attaches the ball rod to the tail piece, then pull the ball rod straight out. Loosen the fittings that hold the tail piece in place and remove it. A replacement tail piece can be installed in the reverse order.

Stopper

If water is leaking past the drain stopper when the basin is full, you may have a faulty O-ring gasket on the stopper. The existing O-ring can be pried off with a flat blade screwdriver and a new one pushed into the groove. Another cause of water getting past the stopper when it is closed is a maladjusted lift rod. Loosening the set screw on the underside of the lift rod will enable you to slide the rod upwards slightly. After re-tightening the set screw, the stopper should sit more securely in the pop-up drain flange.

Resources

• Moen: Single-Handle Lavatory Instruction Sheet
• Moen: Single-Handle Lavatory Exploded Parts View