A spec-driven, step-by-step walkthrough of why water drips from the two bolts that join the tank to the bowl, from worn rubber washers and a tired tank-to-bowl gasket to over-tightened nuts, corroded brass bolts and a hairline crack in the tank, with the exact checks to run in order, the right way to replace the tank-to-bowl kit, and the clear signs that tell you when the fixture itself needs replacing.
Research updated June 2026.
A toilet leaking from the tank bolts almost always has worn rubber bolt washers or a tired tank-to-bowl gasket, not a cracked tank. Drain the tank, then replace the entire tank-to-bowl kit (both bolts, washers and the spud gasket) and snug the nuts evenly by hand feel. If the tank porcelain is cracked, replace the fixture. A one-piece TOTO UltraMax II removes the joint entirely.
Water dripping from the bottom of a toilet tank, right where the two bolts pass through, is one of the most common and most fixable plumbing leaks in any home. People see the drip, watch it pool on the floor or run down the bowl, and assume the tank is cracked or the toilet is done. In reality the great majority of these leaks come from a few inexpensive rubber parts that have simply worn out: the soft washers that seal each tank bolt, and the larger sponge gasket that seals the flush valve where the tank meets the bowl. The bolts themselves rarely fail. What fails is the rubber that keeps water from following the metal through the holes in the porcelain.
This guide is organized the way a careful plumber would diagnose the problem: start by confirming the water really is coming from the tank bolts and not from the supply line, fill valve or base, then work through the causes from the cheapest and most common to the rarest and most serious, and only treat replacing the toilet as the answer once a cracked tank is confirmed. Along the way it explains the parts and specs that control a leak-free tank joint so you can read the situation instead of guessing. For the broadest cross-brand ranking of high-power fixtures, the pillar guide to the best flushing toilets goes wider. This page has one job: explain why your toilet is leaking from the tank bolts and how to stop it.
We do not test toilets in a lab. We compare manufacturer specifications, published MaP (Maximum Performance) flush-test gram scores, trapway diameter and glazing, flush-valve size, EPA WaterSense listings and aggregated owner ratings across major retailers. For diagnosing a tank-bolt leak we lean on the physics of how rubber washers and a spud gasket seal a two-piece tank to its bowl, the failure patterns owners report most often, and the design features (one-piece bodies, brass hardware, oversized gaskets) that make a fixture less likely to weep at the joint. Where the fix is a cheap kit rather than a new toilet, we say so plainly.
A tank-bolt leak is a sealing failure at the joint between tank and bowl, or a source of water that only looks like it comes from the bolts. Naming the right cause is the whole game.
To understand a tank-bolt leak you have to picture how a two-piece toilet is assembled. The tank sits on a shelf at the back of the bowl, and two long bolts (the tank-to-bowl bolts, or tank bolts) drop down through holes in the bottom of the tank, through matching holes in the bowl, and are clamped by nuts underneath. Each bolt has a soft rubber washer under its head inside the tank to keep water from seeping through the bolt hole. Between the tank and bowl, surrounding the flush valve, a large sponge or rubber gasket (the spud gasket, or tank-to-bowl gasket) seals the main water path. When any of these rubber parts hardens, cracks or shifts, water escapes around a bolt or the gasket and drips out under the tank.
That means a true tank-bolt leak comes from a short list of causes: a worn or cracked bolt washer, a hardened tank-to-bowl gasket, nuts that are loose or, just as often, over-tightened, corroded bolts that no longer pull a clean seal, or, less often, a hairline crack in the tank porcelain around a bolt hole. There is also a category of water that pools under the tank but does not come from the bolts at all: a dripping supply line, a leaking fill-valve shank nut, or condensation running down the cold tank. The sections below take each in turn, in the order you should check them, starting with the impostors so you do not tear into a perfectly good tank for nothing.
Before touching a single nut, rule out the things that masquerade as a tank-bolt leak. All of them leave water under the tank, and none need the tank pulled.
Tank condensation, sometimes called tank sweat, is the most common false alarm. In humid bathrooms, or where the incoming water is very cold, moisture in the air condenses on the cold porcelain and runs down the outside of the tank to the floor, often pooling right under the tank where bolt drips would also appear. The giveaway is that condensation shows up in humid weather or after a hot shower, coats the whole outside surface of the tank, and appears whether or not you flush. The fix is an insulated tank liner, a mixing valve that warms the fill water slightly, or better bathroom ventilation, none of which involve the bolts.
The second impostor is a leak from the water supply side. The supply line connects to a shank nut at the bottom of the tank where the fill valve passes through, and a worn washer there, or a loose compression fitting on the supply line, can drip and run along the underside of the tank to the bolt area. To tell these apart, dry everything completely, then wipe the supply connection, the fill-valve shank nut, each bolt head inside the tank, and the gasket area with a paper towel, and watch where the first new water appears. A true bolt or gasket leak shows up under the tank, gets worse right after a flush as the tank refills under pressure, and traces straight up to a bolt or the gasket rather than to the supply fitting.
Two quick tests separate a real tank-bolt leak from an impostor. First, dry everything and wrap a dry paper towel around each bolt and around the supply connection, then flush several times and see which towel wets first and from where. Second, add a few drops of food coloring to the tank water, wait without flushing, and watch the floor: colored water under the tank means a bolt washer or gasket is leaking, while clear water means condensation or a supply drip. These cost nothing and save you from pulling a healthy tank.
The single most common cause of a genuine tank-bolt leak. The soft rubber washer under each bolt head is a wear part, and once it hardens or cracks, water follows the bolt straight through the hole.
Each tank bolt has a rubber washer that sits between the bolt head and the inside floor of the tank, sealing the bolt hole so the water standing in the tank cannot seep down through it. These washers are soft rubber, and like any rubber part they dry out, harden and crack over years of constant submersion. Once a washer loses its pliability, the seal around the bolt breaks and water weeps down the bolt threads to drip out under the tank. A leak that traces straight up to one bolt head, and gets worse as the tank sits full between flushes, is the textbook signature of a failed bolt washer.
The fix is inexpensive and within reach of most homeowners: replace the bolts and washers, ideally with a full tank-to-bowl kit so every rubber part is fresh at once. Shut off the supply, flush to empty the tank, sponge out the last of the water, then loosen the nuts underneath while holding the bolt heads inside to keep them from spinning. Drop in new brass bolts with new rubber washers (and metal washers under the nuts), and snug the nuts evenly. Always replace both bolts and washers together rather than just the leaking one, because a washer that has failed on one side means its twin is the same age and about to follow. Use brass bolts, which resist corrosion far better than plated steel and pull a cleaner long-term seal.
The big sponge gasket between tank and bowl carries the main flush flow, and when it hardens or shifts, the leak can look exactly like a bolt leak because the water exits at the same place.
Surrounding the flush valve, where the tank sits on the bowl, is a large sponge or rubber gasket often called the spud gasket or tank-to-bowl gasket. It seals the main opening through which tank water rushes into the bowl on every flush. Like the bolt washers, this gasket is rubber and degrades with age, going hard, flattening or developing cracks until it no longer seals. When it fails, water escapes from the center of the joint and runs out under the tank, frequently pooling near the bolts, so owners blame the bolts when the gasket is the real culprit. A leak that surges with every flush, rather than dripping steadily, often points to the gasket.
Because the gasket and the bolts share the same joint, the right repair is to replace them together. A complete tank-to-bowl kit includes both brass bolts, both rubber bolt washers, the metal washers and nuts, and the large spud gasket, so a single inexpensive kit refreshes the entire joint. Pulling the tank to reach the gasket also gives you a clear look at the porcelain around the flush-valve opening and the bolt holes, which is exactly where a hairline crack would hide. Refreshing every rubber part at once means you fix the leak whether it was the bolts, the gasket, or both, and you avoid pulling the tank a second time a year later when the part you skipped fails.
When a tank joint leaks, the economical move is a complete tank-to-bowl kit, not a single washer. The bolts, both washers and the spud gasket are all the same age and live in the same water, so replacing one while leaving the rest is how people end up pulling the tank twice in two years. A full kit is a low-cost part, the labor is identical, and it guarantees the leak is fixed at the source rather than chased from one rubber piece to the next.
The nuts hold the rubber compressed against the porcelain. Too loose and the seal weeps, but too tight is the bigger hazard, because cranking on brittle porcelain cracks the tank.
The nuts underneath the bowl shelf clamp the tank down and compress the bolt washers and the spud gasket into a watertight seal. If they are simply loose, the rubber is not pressed firmly enough and water seeps past, which a careful, even snugging can sometimes cure on its own. A tank that was solid for years and then develops a slow weep can occasionally be fixed by tightening the nuts a quarter turn at a time, alternating sides, until the drip stops. This is the cheapest possible fix and worth trying before pulling anything apart, as long as you tighten gently.
Over-tightening is the more dangerous and more common mistake. The clamping force lands on a brittle porcelain tank, and cranking the nuts down hard can crack the tank around the bolt holes, turning a five dollar washer problem into a tank replacement. Tighten only enough to stop the leak and hold the tank firm; the tank should not rock, but it does not need to be bolted like an engine. Hold the bolt head still inside the tank with a screwdriver while you turn the nut, so the bolt does not spin and chew its washer. If the nuts spin without tightening, the bolts are corroded or stripped and need replacing rather than forcing.
Tank bolts only need to be snug enough to compress the rubber and stop the leak. Tighten the two nuts gradually and alternately, a little at a time on each side, and stop the moment the drip stops and the tank is firm. The most common way homeowners turn a cheap repair into a new tank is forcing the nuts down hard and cracking the porcelain around a bolt hole. If the tank still weeps after the nuts are snug, the answer is fresh rubber parts, not more torque.
The bolts are simple, but the wrong material rusts, swells and weeps. A corroded bolt cannot pull a clean seal no matter how new the washer.
Tank bolts live half-submerged in standing water, so material matters. Plated-steel bolts, common in cheap kits, eventually rust, and the corrosion swells the metal, weakens the threads and leaves a rough surface that the rubber washer cannot seal against. A bolt that has rusted at the head inside the tank will weep around its washer even when the washer itself is sound, and a bolt that has corroded at the nut will spin or strip instead of tightening. Rust stains streaking down from a bolt head, or orange water around the bolt hole, are clear signs the hardware is the problem.
The fix is to replace the bolts with solid brass, which does not rust and pulls a clean, durable seal. Brass tank-to-bowl bolts come in most quality kits and are the right choice for any repair, since they outlast the toilet rather than failing again in a few years. While the tank is off, replace both bolts even if only one looks corroded, and pair them with fresh rubber washers and a new gasket. Avoid reusing old hardware to save a few dollars; the entire point of the repair is a joint that seals and stays sealed, and old steel bolts undermine that no matter how careful the installation.
The one cause the fixture cannot survive. When the porcelain is cracked around a bolt hole or anywhere on the tank, no kit will help, and the toilet has to be replaced.
Porcelain is durable but brittle, and a tank can crack from a dropped object, a hard freeze, ground movement, or, most often in this context, over-tightened tank bolts. A hairline crack radiating from a bolt hole, or running down the tank wall, weeps water continuously and pools it under the tank in a way that mimics a worn washer. Unlike a rubber-part leak, a crack often leaks even when the toilet is not flushed, because the standing water in the tank seeps through the crack steadily rather than only on the flush. Drying the porcelain and watching where water reappears, with the help of food coloring in the tank, reveals a crack as the source.
There is no reliable permanent repair for a structural crack in a tank that holds water under pressure. Epoxy and porcelain sealers are at best a short-term stopgap on a hairline crack above the waterline, and a crack at or below the waterline, or one through a bolt hole, means the tank is at the end of its life. Replacing just the tank is sometimes possible if you can source an exact matching tank, but for many models a full toilet replacement is the right and only durable answer. The upside is the chance to buy a model that is harder to leak in the first place, which the picks below address. Our guide on what to do when a toilet is not flushing properly and how to fix it covers related tank and flush-path problems if the bowl is also struggling.
Before deciding the tank is cracked, dry the entire tank inside and out, then add a few drops of food coloring to the tank water and wait twenty minutes without flushing. If colored water appears on the floor under the tank, the path is a crack rather than a flush-only seal leak. If the floor stays dry until you flush, the crack is unlikely and the washers or gasket are the real culprit. This one test prevents both unnecessary replacements and pointless kit swaps.
A side-by-side summary of the causes, ranked roughly from cheapest and most common to hardest. Start at the top and stop when the leak stops. The tinted row is the cause most owners overlook and the one most likely behind a recurring tank-bolt leak.
| Cause | Best For (what it explains) | Typical fix | Cost | DIY? | Likelihood |
|---|---|---|---|---|---|
| Worn bolt washers or gasket | Drip or surge under the tank at the joint | Replace the full tank-to-bowl kit | Low | Yes | Very common |
| Loose tank nuts | Slow weep that started gradually | Snug nuts evenly by hand feel | Free | Yes | Common |
| Tank condensation | Whole tank wet in humid weather, no flush needed | Insulate tank, improve ventilation | Low | Yes | Common |
| Supply line or shank nut drip | Water traces to the supply fitting, not the bolts | Replace supply washer or fill-valve nut | Low | Yes | Moderate |
| Corroded steel bolts | Rust stains, bolts spin or weep at the head | Replace with solid brass bolts and kit | Low | Yes | Moderate |
| Cracked tank or bolt hole | Leaks without flushing, steady weep | Replace the tank or the toilet | High | No | Uncommon |
If we had to name the single most common mistake, it is replacing one bolt washer and leaving the gasket and the second washer in place. They are all the same age and sit in the same water, so the leak comes back within a year and you pull the tank again. Buy the complete tank-to-bowl kit, refresh everything at once, and use brass bolts so corrosion never restarts the problem. And tighten by feel, never by muscle, because the fastest way to turn a cheap repair into a new tank is cranking the nuts down hard and cracking the porcelain around a bolt hole.
If a cracked tank or a chronically poor joint has you buying a replacement, a few design features genuinely lower the odds of a future tank leak. The spec sheet predicts which replacement seals best.
The most leak-resistant fixtures share a handful of traits. A one-piece toilet, where the tank and bowl are a single porcelain casting, eliminates the tank-to-bowl joint entirely, so there are no tank bolts, no spud gasket and no bolt washers to fail, which removes this whole category of leak. Among two-piece models, factory-fitted brass hardware, an oversized sponge gasket and a thick, evenly machined tank shelf bed down more reliably and resist the weeping that plagues thin, cheaply hardware-equipped tanks. None of these guarantees a leak-free life, but together they meaningfully reduce the chance of the joint failures that cause tank-bolt leaks.
Read those traits alongside the core flush specs so you buy once. A toilet that pairs leak-resistant construction with a high MaP score, a wide glazed trapway and a 3 inch or larger flush valve is a fixture you will not have to revisit. MaP, short for Maximum Performance, is the independent test that measures how many grams of waste a toilet clears per flush: 600 grams handles a typical home, 800 grams is strong, and 1,000 grams is the practical ceiling. The three picks below all combine sound, leak-resistant construction with strong flush specs, covering an everyday one-piece default that removes the joint, a sturdy two-piece value option with good hardware, and a clean skirted design.
If a cracked tank or a joint you cannot keep sealed means a new toilet, these three pair leak-resistant construction with a high MaP score and a wide trapway. Each suits a different situation, from a one-piece that removes the joint to a sturdy two-piece value choice.
A one-piece body has no tank-to-bowl bolts, washers or spud gasket to fail, removing this leak category entirely, while a glazed trapway, Tornado flush and 1,000 gram MaP rating at an efficient 1.28 gallons make it the most leak-resistant strong-flush default.
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A canister flush valve, factory brass tank hardware and a thick, evenly machined tank shelf make the Cimarron a dependable, leak-resistant two-piece, with a deep Kohler parts ecosystem that keeps a future tank-to-bowl kit easy to source.
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A one-piece skirted design has no tank joint to weep, gives a flat, easy-to-clean footprint, and pairs a glazed trapway with a strong MaP flush for everyday loads, all at an accessible price point.
Check price on AmazonRun these steps in order. Each is quick, and stopping at the first that solves the problem saves you money and effort. This is the same logic a methodical plumber follows.
Dry the tank inside and out and the floor completely, wrap dry paper towels around each bolt head and the supply connection, then flush several times. If a towel at a bolt or the gasket wets first, it is the joint. If the whole tank surface sweats in humid air, or the supply fitting drips, you have condensation or a supply leak, which need different fixes.
Pop off any bolt caps and tighten each nut a small amount at a time, alternating sides, while holding the bolt head still inside the tank with a screwdriver. Stop the instant the drip stops and the tank is firm. This is the cheapest possible fix and resolves some slow weeps on its own. Never force the nuts, since over-tightening cracks the porcelain tank.
If snugging does not stop the leak, shut off the supply valve, flush to empty the tank, and sponge out the last inch of water so the inside is dry. Disconnect the supply line at the bottom of the tank. A dry, empty tank is essential before you loosen the bolts, since any standing water will pour out the moment the joint breaks.
Hold each bolt head inside the tank and loosen its nut underneath, then lift the tank straight up and set it on a towel. Inspect the bolt holes and the flush-valve opening for hairline cracks, and check the old bolts for rust. This is your one clear look at the porcelain that a kit cannot fix.
Fit the new brass bolts with fresh rubber washers inside the tank, seat the new spud gasket over the flush valve, lower the tank squarely onto the bowl, and add the metal washers and nuts underneath. Snug the nuts evenly and gently, alternating sides, until the tank is firm and level, then reconnect the supply and turn the water on.
If the leak persists after a fresh kit, or if water pools even without flushing, check the porcelain for a hairline crack using food coloring in the tank. A crack through a bolt hole or below the waterline means the tank is finished, and the durable answer is replacing the tank or the toilet rather than chasing the leak.
Resist the urge to chase one rubber part at a time. In the field, the order that solves the most tank-bolt leaks for the least money is confirm it is the joint, snug the nuts gently, then drain and pull the tank and install a complete brass kit, and only then suspect a crack. We have seen homeowners swap a single washer twice in a year on a tank whose gasket was the real leak. Refresh everything at once with brass hardware, tighten by feel, and when you do replace the toilet, choose a one-piece model that has no tank joint to leak in the first place.
Across the major brands, the pattern for leak resistance holds. TOTO leads with one-piece models like the UltraMax II and Aquia IV that remove the tank joint entirely, alongside well-built two-piece designs such as the Drake. Kohler counters with sturdy tanks and quality hardware on the Cimarron, Highline and Santa Rosa. American Standard offers the durable Champion 4 and value Cadet 3, while Woodbridge, Swiss Madison and Gerber bring skirted one-piece styling and the Viper and Avalanche two-piece lines. Whichever brand you choose, the rule is the same: a one-piece body, or a two-piece with brass hardware and a quality gasket installed with care, makes a future tank leak unlikely. If the bowl also clears slowly, our guide on how to improve toilet flush power with seven proven fixes covers the upgrades worth trying, the weak toilet flush fix and its causes walks through each one, and if drainage is the issue, our guide on why a toilet keeps clogging and how to fix it covers the trapway and flush-path checks.
A toilet leaking from the tank bolts is rarely the disaster it looks like. The cause is almost always specific and findable: condensation pretending to be a leak, a supply-line drip, loose nuts, worn bolt washers, a hardened gasket, corroded steel bolts, or, least often, a cracked tank. Work through them in order, starting by confirming the leak is real and trying the gentle nut snug, and most households stop the leak with a low-cost tank-to-bowl kit and an hour of work. When the diagnosis does point to a cracked tank or bolt hole, replace the tank or the toilet with a leak-resistant one-piece model, and the drip stops being part of your bathroom. Confirm the cause first, then check the current price on Amazon for whichever kit or replacement your diagnosis calls for.
Diagnose before you spend. Confirm the water is coming from the joint and not condensation or the supply line, try a gentle, even snug of the nuts, then drain the tank and install a complete brass tank-to-bowl kit, in that order. Most tank-bolt leaks end there for little money. Only replace the toilet if the tank porcelain is cracked. When you do replace, the one-piece TOTO UltraMax II removes the joint entirely and is the most leak-resistant strong-flush pick, with the Kohler Cimarron and Woodbridge T-0019 as solid alternatives.
The usual cause is worn rubber: the soft washer under a bolt head has hardened or cracked, or the larger spud gasket between the tank and bowl has degraded, so water escapes at the joint and drips under the tank. The bolts themselves rarely fail. Replacing the complete tank-to-bowl kit, both bolts, both washers and the gasket, fixes the great majority of these leaks for a low parts cost.
Sometimes, yes. If the rubber is still good and the nuts have simply loosened, a careful, even snug can restore the seal. Tighten each nut a little at a time, alternating sides, while holding the bolt head still inside the tank, and stop the moment the drip stops. Never force them, because over-tightening cracks the porcelain tank. If it still leaks after a gentle snug, the washers or gasket need replacing.
A tank-to-bowl kit is an inexpensive set that refreshes the entire joint between the tank and the bowl. It contains two bolts (ideally solid brass), two rubber washers that seal the bolt holes inside the tank, the metal washers and nuts that go underneath, and the large sponge spud gasket that seals the flush valve. Replacing the whole kit at once ensures the leak is fixed regardless of which rubber part had failed.
Replace the whole kit. Both washers and the gasket are the same age and sit in the same water, so a washer that failed on one side means its twin and the gasket are about to follow. The labor of pulling the tank is identical either way, and a full kit is a low-cost part, so refreshing everything at once avoids pulling the tank a second time within a year or two.
Dry the tank inside and out and watch where new water appears. A bolt or gasket leak traces straight up to a bolt head or the joint and worsens right after a flush as the tank refills. Condensation, or tank sweat, coats the entire outside of the cold tank in humid weather or after a hot shower and appears with no flush needed. If the whole surface is wet without flushing, it is condensation, which insulation or ventilation fixes.
Dry everything, then wrap paper towels around each bolt head and around the supply connection and shank nut at the bottom of the tank, and flush a few times. A bolt or gasket leak wets the towel at the joint, while a supply leak wets the towel at the fitting. Supply leaks often drip whether or not you flush, whereas a gasket leak surges with the flush. The wet towel tells you which to fix.
A leak that surges with each flush usually points to the tank-to-bowl gasket rather than a bolt washer. Flushing sends a rush of water through the joint under brief pressure, and a hardened or cracked gasket lets some escape under the tank, then the drip slows as the tank refills. A steady drip that continues between flushes is more likely a bolt washer. Either way, the full kit addresses both.
Yes, it is a manageable DIY job for most homeowners. Shut off the supply, flush and sponge out the tank, disconnect the supply line, hold each bolt head while loosening its nut, and lift the tank off. Inspect the porcelain, fit the new brass bolts, washers and gasket, lower the tank back squarely, snug the nuts gently and reconnect the water. A second person to steady the tank helps, but it is not strictly required.
Solid brass. Tank bolts live half-submerged in standing water, and plated-steel bolts rust over time, swelling the metal, weakening the threads and roughening the surface so the washer cannot seal. Brass does not corrode, pulls a clean long-term seal, and outlasts the toilet. If a kit comes with steel bolts, swap them for brass; the small extra cost prevents the leak from returning in a few years.
Only snug enough to compress the rubber, stop the leak and hold the tank firm and level. Tighten the two nuts gradually and alternately, a small amount each, and stop as soon as the tank is solid and the drip stops. The tank should not rock, but it does not need heavy torque. Over-tightening is the leading cause of a cracked tank, so tighten by hand feel rather than forcing the nuts down hard.
Spinning bolts mean the bolt or nut threads have corroded or stripped, common with old steel hardware. Hold the bolt head still inside the tank with a flat screwdriver while you turn the nut underneath with a wrench. If it still spins, the bolt is finished and must be replaced. This is a clear sign to install a fresh brass tank-to-bowl kit rather than trying to salvage the old hardware.
Not reliably. A hairline crack above the waterline can sometimes be slowed with epoxy or porcelain sealer as a short-term stopgap, but a crack at or below the waterline, or one through a bolt hole, holds water under pressure and will keep weeping. Porcelain cannot be permanently repaired in that situation, so a cracked tank means replacing the tank with an exact match or replacing the whole toilet.
Dry the entire tank inside and out, then add a few drops of food coloring to the tank water and wait about twenty minutes without flushing. If colored water appears on the floor under the tank without a flush, the source is a crack rather than a flush-only gasket leak. Inspect the porcelain in good light, paying close attention to the area around each bolt hole and the flush-valve opening, where cracks most often start.
The most common fix is inexpensive in parts. A complete tank-to-bowl kit with brass bolts, washers and a gasket is a low-cost item, so a DIY repair is mostly your time, typically under an hour. Calling a plumber adds a service fee for the same job. A full tank replacement, if the tank is cracked, is the costlier end, and is often the point at which replacing the whole toilet makes more sense.
Yes, replace it at the same time. The spud gasket sits in the same joint and the same standing water as the bolt washers, so it is the same age and condition. Pulling the tank to reach a leaking bolt gives you free access to the gasket, and a full kit costs little more than a single washer. Skipping the gasket is how a fixed tank starts leaking again from the center of the joint a year later.
Yes. A one-piece toilet casts the tank and bowl as a single piece of porcelain, so there are no tank bolts, no bolt washers and no spud gasket to fail, which removes this entire leak category. A one-piece TOTO UltraMax II is a strong example. The tradeoff is that one-piece toilets are heavier and usually cost more, but they eliminate the joint that causes tank-bolt leaks in two-piece models.
It is not usually an immediate flood emergency, but it should not be left for long. Even a slow drip runs onto the floor on every fill cycle, where it rots the subfloor, loosens tile and grows mold over weeks. If you cannot fix it right away, shut the supply off between uses and dry the floor often. A spongy or discolored floor behind the toilet means damage is already underway and needs prompt attention.
Start with the DIY route, since most tank-bolt leaks trace to worn washers, a hardened gasket or loose nuts, all of which a complete kit and an hour of work address for little money. Call a plumber when the tank is cracked and needs replacement, when the subfloor is rotted and needs structural repair, or when you have installed a fresh kit and the leak still returns and you need help confirming whether a crack is the cause.
How we rank & our data sources
We do not run physical lab tests. Rankings are built from published, verifiable data and real owner feedback, never paid placement.
Researched by Derek Whitman · Last updated June 28, 2026 · Our review method
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