A dripping or wet supply line is one of the easiest plumbing repairs you can do yourself. No torch, no special skills, and usually under twenty minutes with a single adjustable wrench. This guide walks through every step the way a plumber sequences it, from choosing the right replacement hose to checking for leaks after the job.
Research updated June 2026.
To replace a toilet supply line, shut off the stop valve, flush to drain the tank, and disconnect the old hose at both ends. Thread a new 3/8-inch x 7/8-inch braided stainless steel supply line onto the fill valve shank and the stop valve outlet, hand-tight plus a quarter turn. Turn the water back on, check every joint for drips, and the job is done in under twenty minutes. A 12-inch braided hose fits most standard installs.
The toilet supply line is the short hose that runs from the shutoff valve on your wall or floor up to the bottom of the toilet tank. It is also called the fill line, tank connector, or toilet connector hose. Despite being a small, inexpensive part, a failing supply line is a leading source of bathroom water damage: old rigid chrome or vinyl lines can crack, corrode, or pull loose at their fittings, and a steady drip under the tank often goes unnoticed until the floor or cabinet below is already soaked.
The good news is that supply lines are one of the most standardized parts in plumbing. A single size, 3/8-inch compression inlet and 7/8-inch toilet ballcock nut outlet, fits the stop valve and fill valve on the vast majority of toilets regardless of whether you have a TOTO Drake, a Kohler Highline, a Kohler Cimarron, an American Standard Cadet 3, a Woodbridge T-0001, or a Gerber Viper. Length is the only variable you need to measure before you buy. You do not need to match the brand of the hose to the brand of the toilet.
Old-style rigid chrome supply lines were standard in homes built before the 1990s. They corrode at the ferrule inside the compression fitting and crack under the vibration of daily flush cycles. Vinyl braided lines, common through the 2000s, degrade from UV exposure and chlorine in the water and can split suddenly. Modern braided stainless steel lines, wrapped in a woven metal jacket over a rubber core, resist corrosion, handle water hammer pressure spikes, and generally outlast the toilet they connect to. They are also far easier to route than rigid tubes and cost only a few dollars more.
Signs that your supply line needs replacement include: water on the floor under the tank that is not from condensation, rust stains or green verdigris at either coupling nut, a hose that kinks or looks pinched, a vinyl sleeve that has turned yellow or brittle, any visible crack or weep point on the body of the hose, or any line that is ten or more years old. If you are already replacing a toilet fill valve or a toilet flapper, adding a fresh supply line at the same time is cheap insurance.
Measuring length correctly saves a return trip. Measure straight from the stop valve outlet to the fill valve shank at the bottom of the tank, then add a couple of inches so the hose curves gently without kinking. A line that is too short will be taut and pull at both fittings under pressure, which is a primary cause of leaks. A line that is too long coils under the tank, which is fine as long as it does not kink sharply or press against the porcelain.
| Supply Line | Best For | Inlet | Outlet | Material | Rating |
|---|---|---|---|---|---|
| Braided Stainless (3/8 x 7/8, 12 in) | Most bathrooms | 3/8 in compression | 7/8 in ballcock | Stainless braid | 4.8 |
| Braided Stainless (3/8 x 7/8, 16 in) | Taller stop valves | 3/8 in compression | 7/8 in ballcock | Stainless braid | 4.7 |
| Braided Stainless (3/8 x 7/8, 20 in) | Offset or side valves | 3/8 in compression | 7/8 in ballcock | Stainless braid | 4.6 |
| Braided PVC (3/8 x 7/8, 12 in) | Budget replacement | 3/8 in compression | 7/8 in ballcock | Polymer braid | 4.1 |
| Chrome Rigid (3/8 x 7/8, 12 in) | Matching chrome finishes | 3/8 in compression | 7/8 in ballcock | Chrome metal | 3.8 |
If your stop valve has a 1/2-inch iron pipe (IPS) outlet rather than the standard 3/8-inch compression, look for a supply line labeled "1/2 IPS x 7/8 ballcock" or buy a 3/8-inch compression-to-1/2-inch FIP adapter. A few older homes also have 7/8-inch outlet stop valves; in that case the fitting sizes reverse and you need a line marked accordingly. When in doubt, take a photo of both fittings to the hardware store and match them physically.
Below is the complete short list. Having these ready before you start keeps the job clean and quick.
| Item | Why You Need It | Notes |
|---|---|---|
| Replacement supply hose | The part you are swapping | 3/8 x 7/8 braided stainless, correct length |
| Adjustable wrench or channel locks | Loosen both coupling nuts | Hand-tighten on reinstall, light snug with wrench |
| Towel or small bucket | Catch water in the hose and line | Lay under both ends before loosening |
| Flashlight | See the lock nut under the tank | Phone light works fine |
| Teflon tape (optional) | Extra seal on leaking metal threads | Not needed on rubber-sealed fittings |
Work through the steps in order. None require force, and the most common mistake is overtightening the plastic fill valve nut, which cracks the fitting or the tank. Read each step before you perform it.
The stop valve, also called the shutoff valve, sits on the wall or floor directly behind and below the toilet. Turn it clockwise until it stops moving. If it is a gate valve (a wheel-style handle that requires many full turns), close it fully. If it is a quarter-turn ball valve, rotate the handle ninety degrees so it sits perpendicular to the pipe. Once closed, flush the toilet and hold the handle down to drain as much water from the tank as possible. The tank will not refill once the supply is off. Place a towel or shallow pan directly under the supply line at floor level before you loosen anything, because the hose itself holds a small amount of water that will drain when you disconnect it.
The upper end of the supply line threads onto the fill valve shank at the bottom of the tank. Hold the shank steady from inside the tank with your fingers or the other hand to prevent it from spinning, and use your adjustable wrench to loosen the coupling nut counterclockwise. Once loose, finish unthreading by hand. There will be a small amount of water in the base of the tank and in the valve shank; let it drip onto your towel. If the old nut is plastic (on most modern fill valves) and is stuck, turn steadily and avoid jerking, which can crack the shank or the tank wall around it.
The lower end of the supply line connects to the stop valve outlet with a compression coupling nut. Use your adjustable wrench to loosen it counterclockwise. Water left in the supply line will drain out when the lower end comes free; keep your towel or bucket in place. Once both ends are disconnected, slide the old hose out and discard it. Note the length of the old hose as a guide for your replacement.
With the old hose removed, inspect both connection points. At the stop valve, look for corrosion, cracks in the outlet threads, or a deformed ferrule seat. At the fill valve shank under the tank, look for cracked plastic, stripped threads, or mineral buildup. Wipe both clean with a damp cloth. If the fill valve threads are damaged or the shank is cracked, this is the time to replace the fill valve before connecting a new hose. A new supply line on a cracked shank will leak from day one. If you see heavy corrosion at the stop valve outlet, plan to replace that valve too. Running both repairs while the water is already off saves a second shutdown.
Start at the tank end. Hand-thread the upper coupling nut of the new braided line clockwise onto the fill valve shank. The nut on most braided lines is plastic and seals with a rubber washer inside; it does not require thread tape. Turn until the nut is snug by hand, then use your adjustable wrench to turn it a quarter turn more. That is enough. Overtightening a plastic nut on a fill valve shank strips the threads or cracks the shank, either of which requires replacing the entire fill valve assembly.
Then route the hose down to the stop valve without kinking it. A gentle S-curve is ideal. Thread the lower coupling nut onto the stop valve outlet clockwise. This connection is often metal-to-metal and can use Teflon tape on the threads if the fitting is a male pipe thread type, but most modern supply hoses use a compression seat that seals on its own. Snug by hand, then a quarter to a half turn with the wrench until firm. Do not crank it.
The single most consistent mistake on this job is tightening the upper nut (at the fill valve) too hard. Fill valve shanks on modern toilets, including the TOTO Drake and Drake II, the Kohler Highline, and the American Standard Cadet 3, are made of lightweight plastic that seals with a rubber washer and requires almost no torque. The failure pattern we see repeated in owner reports is: someone cranks the nut down until they are confident there will be no leak, and instead cracks the shank, which either leaks immediately or fails a week later. Hand-tight plus a quarter turn. If it seeps after you turn the water on, snug it a touch more. Never go past a half turn past hand-tight on plastic.
Slowly open the stop valve counterclockwise. Watch the lower fitting first as pressure builds in the line. Then watch the upper fitting at the tank as the tank begins to fill. Let the tank fill completely, then flush once and watch both fittings through the full refill cycle. Dry the area around each connection with a paper towel, wait two minutes, and feel for any wetness. A slow seep at either fitting means the nut needs one more careful quarter turn. If the upper nut is plastic and already feels firm, do not force it further; instead, drain the tank again, remove the nut, check that the rubber washer is seated flat in the fitting, and reinstall. A rolled or misaligned washer is the second most common cause of a leak that does not respond to tightening.
Here are the three supply line types you will encounter and how they compare in real-world use.
A woven stainless jacket over a rubber inner core that resists kinking, handles pressure spikes, and does not corrode. Available in every standard size. The default recommendation for any supply line replacement on TOTO, Kohler, American Standard, or Gerber toilets.
Check price on AmazonA polymer-braided line that costs slightly less than stainless and installs the same way. It degrades faster in high-chlorine water and under UV exposure, so it is a reasonable short-term fix but not the first choice for a home you plan to own for years.
Check price on AmazonA rigid chrome-plated copper line that some homeowners prefer in exposed bathrooms where the finish matches chrome fittings. More prone to cracking at the ferrule over time than braided options, and much harder to route around obstructions. Use only when aesthetics demand it.
Check price on AmazonGetting the length right matters more than people expect. A line that is too short will be taut under normal water pressure, and that tension works on the fittings every day, creating tiny micro-movements that eventually cause a slow seep at one of the couplings. A line that is too long coils or loops, which is harmless as long as no part of the hose kinks sharply. If in doubt, buy the next length up; the extra slack in a 16-inch line on an install that would have fit a 12-inch line causes no problems at all, while a short line does.
If you are not sure what your stop valve outlet size is, a quick visual check gives you the answer. A 3/8-inch compression outlet is narrow, roughly the diameter of a pencil. A 1/2-inch IPS outlet is noticeably wider and has male pipe threads rather than a smooth compression seat. If yours is 1/2-inch IPS, most hardware stores stock supply lines with that inlet, or you can use a 3/8-inch compression x 1/2-inch FIP adapter that screws onto the stop valve, after which a standard supply line threads on normally.
At the tank end, the 7/8-inch ballcock nut is standard across essentially all residential tank fill valves, including the Fluidmaster 400A, Korky QuietFill, TOTO fill valves, Kohler fill valves, and every other major brand. You do not need to match the brand of the hose to the brand of the fill valve.
The most common source of confusion on this point is the difference between a compression fitting and a pipe thread fitting. A compression fitting on a stop valve has a smooth, un-threaded outlet and seals by compressing a ring (the ferrule) into the tube. A pipe thread fitting has visible parallel threads and requires tape to fill the thread gaps. Modern braided supply lines with rubber-seated coupling nuts seal on contact with the seat and need no tape at either end in a typical install. Adding tape to a rubber-seated fitting can actually prevent the fitting from seating properly, causing the very leak you are trying to prevent.
The shutoff procedure should always be the first step. Turn the stop valve clockwise until it stops, then flush the toilet once to clear the tank. Confirming that the tank does not refill tells you the valve is closed. Only then should you put a wrench on either fitting. Working with the water live is not a shortcut; it turns a twenty-minute repair into an emergency.
One detail that makes a real difference in long-term reliability: when you thread the new supply line onto the fill valve shank, make sure the rubber washer inside the coupling nut is fully flat, not curled, folded, or rotated sideways. A washer that is not seated flat will not seal evenly, and you will get a slow drip at the tank fitting that appears only when the water pressure is high, such as after a flush cycle. Take the nut off, press the washer flat with your finger, and reinstall. It costs thirty seconds and is the step that owners who get a repeat leak most often skipped the first time.
Leaks on supply lines fall into two categories. The first is a drip at a fitting, which is almost always caused by a misaligned rubber washer, a cracked washer, or a loose nut. The fix is to close the water, tighten carefully or reseat the washer, and retest. The second category is a leak from the body of the hose itself: a crack in a rigid chrome line, a burst in a vinyl line, or a pinhole in the inner rubber tube of a braided line. A body leak means the hose is done and the whole line must be replaced. A body leak on a braided line is uncommon but does happen in homes with very high water pressure or hard water that accelerates corrosion of the inner tube.
If you are repeatedly getting a slow seep from the upper fitting and the washer looks fine, check whether the fill valve shank itself is cracked or has stripped threads. A cracked shank will weep no matter how carefully you seat the washer, and the fix is a new fill valve. For fill valve guidance, see our guide to the best toilet fill valves of 2026.
The ten-year guideline applies to braided stainless lines in normal conditions. Old rigid chrome lines or vinyl lines should be treated as already past their service life if they are more than eight to ten years old, because the corrosion and cracking that cause failures in those materials typically begin well before the line visually shows damage. A supply line failure that goes unnoticed for even a few hours can cause significant water damage to flooring and subfloor. The cost of replacement is so low, typically a few dollars and twenty minutes, that proactive replacement is nearly always worth it.
Also plan a replacement any time you do other toilet work. Replacing a toilet wax ring when pulling the toilet means the water was off anyway; a new supply line costs almost nothing to add at that point. The same applies when replacing a fill valve, a flapper, or the toilet itself entirely.
A stop valve that leaks from its stem (just behind the handle) has a worn packing. The packing nut sits just below the handle and can usually be snugged a quarter turn to stop the weep. A valve that leaks from its body, or from where it connects to the supply pipe, is a more serious repair that may require soldering or pushing a new push-fit valve onto the copper pipe. If your stop valve is old and gate-style (wheel handle, many turns to close), replacing it with a ball valve is a meaningful long-term reliability upgrade that a plumber can do in under an hour while the main supply is off.
A properly functioning stop valve is the essential safety component in your bathroom supply system. It is the device that lets you isolate the toilet for any repair without turning off water to the whole house. If yours is stiff, slow, or only partly closes, a new supply line will not solve that problem. Budget for the valve replacement separately. See our guide to the best toilet plungers and related accessories for what else belongs in any well-prepared bathroom toolkit.
The best long-term setup is a modern quarter-turn ball-type stop valve paired with a high-quality braided stainless supply line, both replaced at the same time when you first notice either one showing age. The combination costs under thirty dollars in parts total and gives you a toilet supply connection that is easy to shut off in an emergency, seals reliably for a decade or more, and does not corrode or crack at the ferrule the way old rigid chrome or gate-valve systems do. If you are already pulling a supply line, look at the stop valve for five seconds. If it has a wheel handle and is older than ten years, plan to replace it at the next convenient window.
Whether you need a standard 12-inch replacement or a longer line for an offset installation, these are the supply line options that show the strongest owner reliability patterns and the best fit-and-seal feedback across home plumbing forums and hardware retailers. If your job requires more than a new supply line, the best flushing toilets guide covers full toilet replacement options with MaP scores and efficiency data.
| Product | Length | Inlet | Outlet | Rating | Check Price |
|---|---|---|---|---|---|
| Fluidmaster 12-inch Braided Stainless | 12 in | 3/8 compression | 7/8 ballcock | 4.8 | Check price |
| Fluidmaster 16-inch Braided Stainless | 16 in | 3/8 compression | 7/8 ballcock | 4.7 | Check price |
| Watts Premier 12-inch Stainless | 12 in | 3/8 compression | 7/8 ballcock | 4.7 | Check price |
| Korky 20-inch Braided Stainless | 20 in | 3/8 compression | 7/8 ballcock | 4.6 | Check price |
| BrassCraft 12-inch Stainless | 12 in | 3/8 compression | 7/8 ballcock | 4.5 | Check price |
The standard is a 3/8-inch compression fitting at the stop valve end and a 7/8-inch ballcock nut at the fill valve end. This fits the fill valve and stop valve configuration on nearly all residential toilets in the United States, including TOTO, Kohler, American Standard, Woodbridge, Swiss Madison, and Gerber. Length is the variable: 12 inches is the most common, with 16 and 20 inches available for longer runs.
Most replacements take fifteen to twenty minutes, including shutting off the water, disconnecting both ends of the old line, threading on the new hose, and checking for leaks. First-timers working carefully can expect closer to thirty minutes. The longest parts of the job are usually finding and closing the stop valve and waiting to confirm that no drips appear after restoring water.
Yes. It is one of the most accessible plumbing repairs available to a homeowner. The job requires only an adjustable wrench, a towel, and a new hose. No soldering, no plumbing cement, and no special skills are needed. The main cautions are to close the stop valve before starting and to tighten the plastic fill valve nut carefully, only hand-tight plus a quarter turn.
The 3/8-inch measurement refers to the outer diameter of the compression fitting that attaches to the stop valve. A 1/2-inch supply line has a larger inlet, matching a 1/2-inch iron pipe (IPS) threaded stop valve outlet. Most modern homes have 3/8-inch compression stop valves. Older homes, particularly those with plumbing from the 1970s or earlier, may have 1/2-inch IPS outlets. Check which you have before buying a replacement.
Generally no. Both standard connections, the 7/8-inch ballcock nut at the fill valve and the 3/8-inch compression fitting at the stop valve, seal with rubber washers or compression seats and do not require thread tape. If your stop valve has male pipe threads (NPT/IPS type) rather than a compression outlet, two to three wraps of Teflon tape on those threads before threading the supply line on will help seal the joint.
The most common cause is a rubber washer inside the coupling nut that is misaligned, curled, or worn. Close the stop valve, drain the tank, remove the nut, flatten the washer with your finger and reinstall. If the washer looks cracked or hard, replace the entire supply line. A leak that continues after the nut is properly tightened can also mean the fill valve shank is cracked, in which case the fill valve needs to be replaced.
Hand-tight plus a quarter turn with a wrench is the correct torque at both fittings. The upper nut on a fill valve shank is plastic and seals with a rubber washer; it does not need heavy torque and will crack if overtightened. The lower compression nut at the stop valve also seals by compressing a rubber seat rather than relying on thread friction. If a connection seeps after a quarter turn, add small increments, not a full extra turn.
Braided stainless steel supply lines typically last ten to fifteen years or longer in normal conditions. Rigid chrome lines and vinyl-braided lines have shorter service lives, often failing between eight and twelve years as corrosion or plastic degradation progresses. Plumbing professionals commonly recommend replacing all supply lines every ten years as a precaution, and replacing old chrome or vinyl lines immediately with braided stainless regardless of their age.
Yes, if the hose is kinked, pinched, or partially blocked with sediment, it restricts flow to the fill valve and the tank refills slowly. A hose that is too short and pulled taut can kink at a fitting. Replacing the kinked line with a correctly sized braided hose that routes in a gentle curve resolves slow fill in most cases. Also check that the stop valve is fully open, since a partly closed valve is the more common cause of slow tank filling.
Yes for most applications. Braided stainless lines are more flexible, easier to install in tight spaces, and far less prone to the ferrule corrosion that causes chrome lines to fail at their fittings. Chrome rigid lines have an aesthetic advantage in exposed locations where finish matching matters, but their rigidity makes them prone to cracking under repeated vibration and hard-water mineral buildup at the ferrule. Braided stainless is the standard professional recommendation for toilet supply line replacement.
A burst supply line releases full line pressure into the bathroom continuously until the stop valve is closed or the main water is turned off. Even a moderate flow rate can put hundreds of gallons into the space in an hour, damaging flooring, subfloor, ceilings below, and stored items nearby. This is why proactive replacement of old vinyl or chrome lines before they fail is strongly recommended, and why a properly functioning stop valve matters so much.
Yes. The tank is already drained and the upper fitting is already disconnected, so adding a new supply line costs only a few minutes and a few dollars in parts. Reusing an old supply line on a new fill valve is a missed opportunity to replace a potential failure point. Owner reports consistently show that the next leak after a fill valve job often comes from a reused old supply line failing at its fitting weeks or months later.
No. Washing machine supply hoses use a 3/4-inch GHT (garden hose thread) fitting that does not match the 3/8-inch compression and 7/8-inch ballcock fittings on a toilet supply system. Using the wrong hose type will either not thread on at all or will leak because the thread pitch and seat geometry do not match. Always use a supply line specifically labeled for toilet connection.
Dry both the supply hose and the stop valve body thoroughly with a paper towel, then wait two minutes with the water on. Touch the fitting at the base of the tank, the body of the hose, the connection at the stop valve, and the stem and body of the stop valve itself. Wetness isolated to the upper coupling nut points to the supply line's tank fitting; wetness at the stem behind the stop valve handle points to the valve's packing nut; wetness at the lower coupling nut is the supply line's lower fitting.
A vibrating or hammering supply line usually means the stop valve is not fully open, causing turbulent flow through a restricted opening, or that household water pressure is very high. Open the stop valve fully and recheck. A persistent water hammer bang when the fill valve closes is a pressure issue best addressed with a water hammer arrestor installed on the supply line. A hissing from the line body usually points to a small internal leak and means the hose should be replaced.
Hold a measuring tape or a length of string from the center of the stop valve outlet to the fill valve shank at the base of the tank, following the curve the hose will naturally take. Add two to three inches for routing clearance. If your measurement falls between standard lengths, buy the next size up. A 12-inch line is the starting point for most standard close-coupled installs; move to 16 or 20 inches if the stop valve sits further from the tank than average.
Yes. A slow seep at a supply line fitting that goes unnoticed can wet the floor, cabinet, and subfloor over days or weeks, creating conditions for mold growth in materials that stay damp. This is one of the main reasons plumbing inspectors and insurance adjusters look at supply line age during inspections. Replacing old lines and checking for drips after each supply line job prevents this category of damage.
The 7/8-inch fitting is the upper coupling nut that threads onto the fill valve shank at the bottom of the toilet tank. This size, sometimes called a ballcock nut because it fits the older ballcock fill valve design as well as modern column valves, is standard across virtually all residential toilet fill valves sold in North America. It seals with a rubber washer inside the nut and does not require tape or sealant.
Apply penetrating lubricant to the nut and let it soak for five to ten minutes. Then use channel-lock pliers for a firm, steady grip and try turning counterclockwise without jerking. If the nut is plastic and is on the fill valve shank, hold the shank inside the tank to prevent it from spinning, which can crack the shank or the tank. A nut that absolutely will not move can be carefully cut with a utility knife or hacksaw blade, keeping the blade away from porcelain. Replace the fill valve if the shank is damaged during removal.
Replacing a toilet supply line is a twenty-minute repair that requires only an adjustable wrench and a towel. Close the stop valve, drain the tank, disconnect both ends of the old hose, and thread a new 3/8-inch x 7/8-inch braided stainless line onto the fill valve shank and stop valve outlet, hand-tight plus a quarter turn at each end. A 12-inch line fits most standard bathrooms; measure and add two to three inches if your stop valve sits further from the tank. Braid the stainless line every time over chrome or vinyl: it lasts longer, resists corrosion, and is far less likely to crack at the ferrule. Replace the supply line whenever you replace the fill valve, flapper, or wax ring, because the tank is already drained and the marginal cost of a new hose is nearly zero.
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