Toilet Supply Line - Toilet Water Connector Repair Guide

A toilet supply line is the flexible water connector that runs from the shutoff valve at the wall or floor to the fill valve under the toilet tank.

Toilet Supply Line diagram — labeled parts, dimensions, and installation context

What It Is

This small connector carries clean water to the toilet each time the tank refills after a flush. Modern supply lines are usually braided stainless steel over a flexible tube, though older installations may use rigid chrome tube or older plastic connectors.

Because it stays under pressure all the time, it is a part that matters more than its size suggests. A failed supply line can leak continuously or burst and cause major bathroom and floor damage very quickly.

Types

Common types include braided stainless steel connectors, polymer-braided lines, rigid risers, and different end sizes such as 3/8-inch compression by 7/8-inch ballcock. Length and routing matter because the line should not kink or rub sharply against the wall or tank.

Where It Is Used

A toilet supply line is used at the water connection beneath almost every tank-type toilet. It links the fixture stop or angle stop to the fill valve shank under the tank.

How to Identify One

Look behind or beside the toilet near the floor. The supply line is the narrow tube running from the shutoff valve to the bottom of the toilet tank.

Replacement

Replacement is recommended when the line shows corrosion, bulging, kinks, cracking, damaged nuts, or age of unknown origin. It is commonly replaced during toilet installation, shutoff valve work, or any repair involving the tank connection.

Toilet Supply Line — FAQ

How often should a toilet supply line be replaced?

There is no universal replacement date, but many plumbers replace it whenever a toilet is changed or when the line shows age or wear. It is a low-cost part compared with the damage a leak can cause.

What size is a toilet supply line?

A common residential line uses a 3/8-inch compression connection at the shutoff valve and a 7/8-inch ballcock nut at the toilet fill valve. Measuring the existing connections is still the safest way to buy the right part.

Can I reuse the old toilet supply line after replacing a toilet?

It is better not to. Reusing an old connector saves very little money and keeps an older pressure part in service at one of the most leak-prone points in the bathroom.

Why is my toilet supply line leaking at the nut?

The connection may be cross-threaded, overtightened, undertightened, or using a damaged washer or ferrule. If the line has been bent or twisted, replacement is usually smarter than trying to force it tighter.