Should I replace my toilet supply line and with what?

Replace it if you see any of these:

• Drips or dampness at either end of the line, or a wet spot on the floor below.
• Rust, crust or corrosion on the nuts or the braid.
• A kink or a hard bend in the line.
• A stiff, cracked or bulging hose.
• A repair nearby. If you are replacing the fill valve, the shut-off valve or the whole toilet, put on a new line at the same time.

Supply lines are worth taking seriously because they carry water under pressure whenever the valve is open. Fluidmaster says its Click Seal design controls torque during hand tightening "to prevent supply line failure and resulting water damage." A line that fails leaks until someone notices, and a slow leak behind a toilet can go unseen for a long time.

If your toilet's line is still in good shape and connections are dry, leave it. Check it whenever you are near it. Our page on how to know when to replace a toilet covers the other signs a toilet is due for work.

Look for a flexible line with a polymer core covered in braided stainless steel wire. Fluidmaster describes its toilet lines this way and says they are "built with a tough polymer core and covered with a braided stainless steel wire." Its listed specifications for the Click Seal line are a burst strength of up to 1500 PSI and a torque rating of 15 to 20 inch-pounds. It also says the connector is lead free, with a weighted average lead content of 0.25 percent or less. Those figures are for one maker's product, so check the package of the line you buy.

Match these details:

1. 1The shut-off valve end. Toilet lines usually connect to the valve outlet with a metal nut. The nut must fit the outlet on your valve. Take the old line with you, or note the size stamped on the valve.
2. 2The fill valve end. The other end has a nut that threads onto the fill valve shank under the tank. Fluidmaster calls this the plastic nut.
3. 3Length. Pick a line long enough to reach without pulling tight, but not so long that it is coiled and kinked behind the toilet.
4. 4The connector style. BrassCraft warns against using its stops "with connectors having a solid brass cone or bull nose design" because "fractures can develop." Check the end that meets the valve, and do not force a mismatched end.

The plumbing code also cares about flexible connectors. The 2024 International Plumbing Code says "a reduced-size flexible water connector installed between the supply pipe and the fixture shall be of an approved type." Buy a connector sold for plumbing use.

These steps follow Fluidmaster's instructions, with details from Korky and Kohler.

1. 1Turn off the water at the shut-off valve. If the valve is stuck or leaks, you may need to shut off the water at the main. Our guide on how to shut off water to a fixture shows how these valves work.
2. 2Empty the tank. Flush, then hold the handle down. Korky says to place a bucket under the tank and disconnect the supply line from the fill valve, letting the excess water drain into the bucket.
3. 3Remove the old line and clean the threads. Fluidmaster's instructions say to remove the old supply connector and clean all connector threads.
4. 4Flush the pipe if the valve is new. Kohler's guide says to turn on the water and "allow water to flow through the supply pipe to flush the system of any debris before connecting fill valve." Aim the valve outlet into a bucket and open it briefly.
5. 5Connect the valve end. Thread the metal nut onto the shut-off valve. Fluidmaster's steps say to tighten it 1/2 turn beyond hand tight. It notes that you only need an adjustable wrench to snug this nut.
6. 6Connect the fill valve end. With a Click Seal line, Fluidmaster says to turn the Click Seal nut counterclockwise until the threads align, then gently turn it clockwise and hand tighten until it clicks. It says "tools are not recommended nor needed to install the Click Seal nut." The click tells you the nut is sealed. On other lines, follow the package instructions, and do not use a wrench on plastic nuts unless the maker says to.
7. 7Turn on the water slowly. Korky says to turn the supply on slowly and inspect the base of the tank while it fills.
8. 8Check for leaks. Look at the shut-off valve. Fluidmaster says that if a leak appears, "tighten nut just enough to provide a leak-free joint," and adds "do not over tighten shut off valve." Then flush a few times. Korky says to watch the bottom of the toilet for leaks during test flushes.

One quirk of the Click Seal line: it clicks in only one direction. Fluidmaster says the line "will only click in the direction it is tightened. If the connector clicks when twisting, you are twisting it the wrong way." That is why a line can click when you try to remove it.

• Over-tightening. BrassCraft warns, about its valves, that overtightening "can cause product to crack and fail over time." A leaking nut often needs a clean seat or a new line, not more force. If a joint drips, loosen it, check that everything is square and clean, and retighten.
• Kinks and sharp bends. Route the line in a gentle curve.
• Reusing a worn line on a new valve. Put a fresh line on when the valve or fill valve changes.
• Skipping the check. Look again after an hour and again the next day. A drip that appears later is easier to fix than a soaked floor.

Keep a towel or small bucket under the connections while you work, because some water always stays in the old line and the fill valve. If you are also changing the fill valve, do that first, so the new line only has to be connected once. Our guide on how to adjust a Fluidmaster fill valve covers the water level setting after the swap.

If the shut-off valve itself is stuck, corroded or dripping, fix that first. A new line on a bad valve will not solve the problem, and our guide on how to replace a toilet shut-off valve shows what that job involves. If the toilet rocks when you move it, see why a toilet rocks and how to fix it.

HQ Plumbing and Air can replace a supply line, the valve behind it, or the whole toilet. We are licensed and insured, we give free estimates, and you get the price up front.