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How to Tighten Water Supply Line Connectors

Updated: Feb. 28, 2020

Leak prevention tip

toilet water supply lineFamily Handyman
Hand-tightened compression nuts for water supply lines always seem to need an extra turn with pliers. But a big part of the problem is low-quality supply lines.

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Toilet water supply line installation

toilet water supply line with reinforcing ribs

Better-quality toilet water supply line

Buy a toilet water supply line that has a metal nut or a reinforced plastic nut.

If it were up to us, no manufacturer would be allowed to use cheap plastic compression nuts on supply lines. This question is one we hear often. In fact, one of our field editors just told us his toilet tale of woe. Hand-tightening caused a leak and pliers-tightening caused the compression nut to crack—days after he installed the supply line. The result was a small flood.

Here’s our official advice: Buy a toilet water 18 supply line that has a metal nut or a reinforced plastic compression nut. If you can’t find one, tighten the regular plastic nut in two stages. First, tighten it enough to stop the water from leaking. Then come back a few hours later (when the rubber gasket has compressed a bit) and snug it up a tad more. Never crank on a plastic nut with pliers.

Required Tools for this toilet water supply line Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

  • Rags

Required Materials for this toilet water supply line Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here’s a list.

  • Supply line with metal or ribbed plastic nut