Pack Plumber's Putty Into Under-Sink Slip Joints to Stop Slow Leaks
The Problem
The under-sink waste pipe sold at most hardware stores is cheap, imprecise plastic, and the slip joints that connect it rely on a hand-tight nut and a single washer. Over time — especially with the vibration of a garbage disposal — those joints can loosen and start to weep, leaving a slow drip in the cabinet you don't notice until the bottom is wet.
The Technique
- As you assemble the slip joint, add a little plumber's putty to the connection before tightening.
- Warm a chunk of putty in your hands and roll it into a thin snake — the same way you'd prep it for seating a sink strainer.
- Pack it into the joint, then hand-tighten the slip nut.
The putty fills the small gaps in a loose-fitting connection and helps keep the joint from working loose and weeping. (Plumber's putty is the soft, clay-like sealant that comes in a small tub — the same material used to seat a sink drain flange in the bottom of the basin.)
Worth knowing — this is a debated shortcut, not standard practice. A slip joint is engineered to seal with its nylon or rubber slip washer compressed against the pipe; putty isn't part of that design. Many plumbers avoid putty here because it can ooze out, doesn't bond, and can hide a washer that's missing or seated crooked. Do it right first: confirm the slip washer is present and seated square, and tighten the nut properly. If a correctly assembled joint still seeps, treat putty as a temporary patch on a cheap fitting — and plan to replace the connector rather than relying on it.