Step-by-step fix
Step 1: Make sure the supply line is really the problem
- Look behind the toilet and dry the shutoff valve, the supply line, and the tank connection with a towel.
- Flush once, then watch closely as the tank refills.
- Check where the water first appears: at the valve nut, along the hose, or at the tank connection.
- If the hose is cracked, rust-stained, kinked, bulging, or dripping from the crimped ends, replace the toilet water supply line.
- If water is coming from the shutoff valve body, the fill valve shank inside the tank, or from under the toilet, this repair will not solve the root cause.
If it works: You have confirmed the leak or wear is at the toilet water supply line or its end connections.
If it doesn’t: If the leak starts at the shutoff valve or tank hardware instead, repair that part first before replacing the line.
Stop if:- The shutoff valve is leaking from the valve body or stem.
- The floor around the toilet is soft, swollen, or shows signs of hidden water damage.
- You cannot clearly tell where the leak starts.
Step 2: Shut off the water and drain the line
- Turn the toilet shutoff valve clockwise until it stops.
- Flush the toilet and hold the handle down to empty as much water from the tank as possible.
- Place a small bucket or pan under the shutoff valve area.
- Use a towel to catch the small amount of water still left in the supply line.
If it works: The tank has mostly drained and the line is no longer under pressure.
If it doesn’t: If the valve does not fully shut off and water keeps refilling the tank, you may need to shut off the home's water before continuing.
Stop if:- The shutoff valve will not close or starts leaking heavily when you turn it.
- The valve or pipe moves in the wall or floor when you try to operate it.
Step 3: Remove the old toilet water supply line
- Loosen the nut at the toilet tank connection first, then loosen the nut at the shutoff valve.
- Let the remaining water drain into the pan.
- Remove the old line and keep it nearby to compare length and end fittings.
- Check both connection points for old rubber pieces, debris, corrosion, or damaged threads, and wipe them clean.
If it works: The old line is off and both connection points are clean and ready for the new line.
If it doesn’t: If a nut is stuck, apply steady pressure with the wrench and support the valve gently so you do not twist the pipe.
Stop if:- The shutoff valve, pipe, or tank fitting starts twisting instead of the nut loosening.
- Threads are cracked, badly corroded, or damaged enough that the new line will not seat properly.
Step 4: Match and install the new line
- Compare the new line to the old one for length, end sizes, and connection style.
- Thread the tank end on by hand first to avoid cross-threading, then thread the shutoff valve end on by hand.
- Tighten each connection snugly with a wrench after hand-threading. Do not force it or overtighten.
- Route the line in a gentle curve without a sharp bend or twist.
If it works: The new line is installed with both ends seated squarely and the hose is not kinked.
If it doesn’t: If the nut will not thread easily by hand, back it off and re-align it before tightening again.
Stop if:- The new line does not match the connection sizes or type.
- A fitting cross-threads or will not seat flat.
- The hose must be stretched tight or sharply looped to reach.
Step 5: Turn the water back on slowly and check for drips
- Open the shutoff valve slowly while watching both ends of the new line.
- Let the tank fill completely.
- Dry both connections with a towel, then touch around each nut and under the hose to check for fresh moisture.
- If you see a small drip at a connection, gently tighten that nut a little more and recheck.
If it works: The tank refills and both ends of the supply line stay dry.
If it doesn’t: If a connection still drips after a small retightening, shut the water back off, disconnect that end, and check for misalignment or the wrong fitting.
Stop if:- Water sprays or runs steadily from a connection.
- The shutoff valve begins leaking from the stem or body while the line itself stays dry.
Step 6: Verify the repair holds during normal use
- Flush the toilet several times and watch the line during each refill cycle.
- Check again after 10 to 15 minutes for slow seepage at either connection.
- Run your hand or a dry tissue under the line and around both nuts to confirm everything is dry.
- Leave the area clean and keep an eye on it over the next day for any delayed drips.
If it works: The toilet refills normally and the new supply line stays dry during repeated use.
If it doesn’t: If moisture returns, recheck which fitting is leaking and confirm the replacement line is the correct size and connection type.
Stop if:- Water is appearing from somewhere other than the new line.
- The toilet, shutoff valve, or nearby flooring shows signs of ongoing hidden leakage.
Replacement Parts
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FAQ
How do I know what size toilet water supply line to buy?
Match both ends and the length of the old line. Most toilets use a shutoff valve connection at the wall and a larger connection at the tank, but you should verify your actual fittings before ordering.
Should I use thread tape on a toilet water supply line?
Usually no on the supply line nuts themselves, because those connections typically seal with a washer or built-in gasket. Use the line exactly as its fittings are designed to connect.
Can I reuse the old supply line if it only leaked once?
It is better to replace it. Once a toilet supply line has started leaking, especially if it is older, corroded, or kinked, replacement is the safer long-term fix.
How tight should the supply line nuts be?
Start by threading them on by hand, then tighten them snugly with a wrench. Avoid cranking down hard, because overtightening can damage the fitting or washer and cause leaks.
What if the shutoff valve leaks after I replace the line?
That points to a valve problem, not a supply line problem. If the valve leaks from the stem or body, the valve likely needs repair or replacement.