Toilet Closet Bolts: Size, Material and Installation

Toilet closet bolts -- also called toilet floor bolts, johnny bolts, or toilet anchor bolts -- are the small threaded fasteners that secure your toilet to the floor flange. They slide into the slots on the closet flange, extend upward through the toilet base holes, and are tightened down with nuts and washers. Despite being hidden from view, they are one of the most structurally critical fasteners in your bathroom. A failed or corroded closet bolt can cause the toilet to rock, the wax seal to break, and sewage water to leak beneath your floor -- leading to rot and mold that can cost thousands to repair.

This guide covers the full picture: standard sizes and specifications, material choices, what brands like TOTO, Kohler, American Standard, Woodbridge, Swiss Madison, and Gerber actually specify in their installation manuals, and step-by-step installation instructions that apply to the vast majority of residential toilets.

What are toilet closet bolts and why do they matter?

The closet flange -- a ring typically made of PVC, ABS, or cast iron -- sits at or slightly above the finished floor surface. It has two slots positioned 180 degrees apart. The head of each closet bolt drops into one of these slots and is rotated so the flat sides of the bolt head grip the underside of the flange ring. When the toilet base slides down over the bolts, the two bolt holes on the toilet base align with the upward-projecting bolt shafts. Washers, a plastic positioning cap, and nuts are then installed on top to clamp the toilet firmly to the floor.

Because this connection bears the full weight of the toilet plus any person sitting on it -- potentially 350 pounds or more for models rated to ADA-compliant weight limits -- the integrity of the bolt, the flange, and the floor substrate all work together. A closet bolt cannot compensate for a broken flange or a rotted subfloor, but a corroded or undersized bolt can fail even when the rest of the assembly is sound.

What is the standard size for toilet closet bolts?

Understanding closet bolt dimensions requires looking at several measurements:

The 5/16-18 UNC standard is near-universal in the United States regardless of toilet brand. TOTO's installation instructions for the Drake (CST744), Drake II (CST454), UltraMax II (MS604114), and Aquia IV (CWT447MFG) all specify the standard 5/16-inch bolt pattern with a 12-inch rough-in. Kohler's Highline and Cimarron series, American Standard's Champion 4 and Cadet 3, Woodbridge's T-0001, Swiss Madison's Sublime series, and Gerber's Viper and Maxwell series all share the same bolt specification. The variation you encounter is in rough-in distance -- 10, 12, or 14 inches -- which refers to the distance from the finished wall to the center of the drain, not to the bolts themselves.

What materials are toilet closet bolts made from, and which is best?

In a bathroom environment, the area around the toilet base is subject to repeated cleaning with water, cleaners, and the moisture that naturally accumulates from a working toilet. Over a 5 to 10 year period, zinc-plated steel bolts commonly develop rust that makes them nearly impossible to remove without cutting. This creates a secondary problem: using a hacksaw or reciprocating saw at floor level, near a wax ring and a drain, is messy and risks damaging the flange. Stainless steel bolts add only a small premium to the project but can typically be unthreaded normally when you next need to pull the toilet.

Bolt kits from brands like Sioux Chief, Oatey, Fluidmaster, and Danco dominate the hardware aisle. Sioux Chief's stainless steel closet bolt kits (part 887 series) and Oatey's stainless kits are among the most widely stocked and specified. These kits typically include two bolts, two plastic positioning washers, two metal washers, two hex nuts, and two plastic caps that snap over the finished assembly for a clean appearance. This kit format is what most plumbing references describe when they say "replace closet bolts."

When should you replace toilet closet bolts?

Signs that closet bolts need attention include:

• Toilet movement or rocking: Even slight movement can break the wax seal and allow sewer gas to enter. Tightening the nuts may help if the bolts are intact, but if the bolt is corroded or the flange is broken, replacement is required.
• Rust staining on the floor around the toilet base: This indicates that the exposed bolt shaft is corroding and the moisture is wicking under the toilet base. Rust staining at this location often predicts a bolt that will fail or seize within the next year or two.
• Stripped or spinning bolt: If a bolt spins rather than threading the nut down, the bolt head is no longer gripping the flange slot. The toilet must be lifted and the bolt repositioned or replaced.
• Broken or sheared bolt: Overtightening -- especially on porcelain that is thinner at the base holes -- can snap a bolt. A snapped bolt requires toilet removal to replace.
• Installation on a new toilet: New toilets are typically packaged without closet bolts; the hardware kit is sold separately or installed from an existing set. If the existing bolts are more than five years old or show any corrosion, replace them as part of the new toilet installation.

One nuance worth noting: if your toilet rocks but the bolts appear intact, the issue may not be the bolts at all. A cracked flange, a rotted subfloor, or a toilet base that is warped can all produce rocking that tightening bolts will not fix. Tightening closet bolts on a cracked toilet base is particularly dangerous -- porcelain fractures can be sudden and can cause injury. For toilets from American Standard's Champion 4 or Cadet 3 lines, Kohler's Highline, or TOTO's Drake series, the manufacturer installation documentation is the authoritative source for maximum torque values, though most manuals simply say "hand-tight plus one-quarter turn" to avoid specifying a value that varies by floor condition.

How do you install toilet closet bolts correctly?

Tools and materials you will need

• Stainless steel closet bolt kit (two-pack; 3-1/2-inch bolts if you have thick tile floors, standard 2-1/4-inch for typical floors)
• Wax ring (replace whenever you pull a toilet)
• Adjustable wrench or 1/2-inch socket wrench
• Hacksaw or oscillating tool with metal cutting blade
• Putty knife or scraper
• Old towels or a bucket to capture water from the tank and bowl
• Sponge or wet-dry vacuum
• Level (optional but recommended)
• Silicone caulk (optional; some codes require caulking the toilet base to the floor)

Step-by-step installation

Step 1 -- Shut off the water supply. Locate the shutoff valve behind or below the toilet and turn it clockwise until closed. Flush the toilet once to empty most of the tank. Use a sponge or wet-dry vacuum to remove remaining water from the tank and bowl so the toilet is light enough to lift.

Step 2 -- Disconnect the supply line. Unscrew the supply line nut from the fill valve at the bottom of the tank. Have a towel ready for any residual drip.

Step 3 -- Remove the toilet. Pop the plastic caps off the existing closet bolt nuts at the toilet base. Use an adjustable wrench to loosen and remove the nuts and any washers. Grip the toilet at the bowl and tank junction, rock it gently to break the wax seal, and lift straight up. Set the toilet on its side on an old towel or cardboard so you do not crack the tank. Do not set it on the wax ring side.

Step 4 -- Remove old bolts and clean the flange. Lift the old bolts out of the flange slots. Use a putty knife to scrape all old wax from the flange surface and the toilet horn. Wax remnants left on the flange face prevent the new wax ring from sealing properly. Inspect the flange carefully: look for cracks, missing sections, or the flange sitting below floor level. A flange that is broken or sunken needs to be repaired or replaced with a flange repair kit before proceeding -- new closet bolts cannot overcome a compromised flange.

Step 5 -- Install the new closet bolts. Slide the head of each new stainless steel bolt into the slots in the flange, one on each side, positioned at the 3 o'clock and 9 o'clock position (in line with the distance-from-wall centerline, perpendicular to the wall itself). Rotate each bolt head so the flat sides grip the underside of the flange ring and the bolt stands vertical. Slide the plastic positioning washers (included in most kits) over the bolt shafts to hold them upright and centered on the flange while you work. If you do not have positioning washers, a small amount of plumber's putty around the base of the bolt can temporarily hold them upright.

Step 6 -- Install the new wax ring. Wax rings are sold with or without a polyethylene horn extension. For standard installations where the flange is at or above floor level, use a standard wax ring without an extension. For flanges that sit below the finished floor surface -- a common result of tile additions -- use a thick wax ring or a wax ring with a plastic horn extension. Press the wax ring onto the toilet horn (not onto the flange) with the wax side facing outward. The ring should be centered on the horn opening.

Step 7 -- Set the toilet. With a helper if the toilet is heavy -- a two-piece toilet like the Kohler Highline or American Standard Champion 4 typically weighs 55 to 90 pounds for the combined assembly, while one-piece models like the TOTO UltraMax II or Woodbridge T-0001 can reach 90 to 120 pounds -- align the toilet base holes with the upright closet bolts and lower the toilet straight down. Do not set it and slide it -- doing so smears and compromises the wax seal. Apply your body weight by pressing down on the toilet rim evenly to compress the wax ring fully.

Step 8 -- Secure the toilet. Slide the metal washers over each bolt, followed by the hex nuts. Hand-tighten the nuts, alternating between sides to keep the toilet level, until snug. Then use the adjustable wrench to tighten each nut an additional quarter turn, again alternating sides. Check that the toilet does not rock. If it rocks slightly on an uneven floor, plastic toilet shims (sold separately) can be inserted under the toilet base before final tightening. Do not overtighten -- you are threading a metal nut onto a bolt that is pressing against a porcelain base, and cracking the base is a real risk. The correct feel is firm resistance with zero toilet movement, not maximum force.

Step 9 -- Trim the bolt shafts. Most stainless steel bolts extend several inches above the nut after installation. Use a hacksaw or oscillating tool to trim each bolt shaft so that approximately 1/4 inch protrudes above the nut. This allows the plastic decorative caps to snap on cleanly. Trim slowly to avoid putting lateral force on the toilet base during cutting. File or deburr the cut end if you are placing the cap on immediately, so the cap snaps down cleanly.

Step 10 -- Reconnect and test. Reattach the supply line to the fill valve. Slowly open the shutoff valve and allow the tank to fill. Flush two or three times and inspect the toilet base and supply line connection for any leaks. Check that the toilet does not rock. Snap the plastic caps over the bolt stubs. If local code requires it, apply a bead of silicone caulk around the toilet base, leaving a small gap at the back to allow detection of any future wax ring leak.

Closet bolt installation for specific toilet types

The basic installation process applies across brands, but a few model-specific notes are useful:

TOTO Drake and Drake II (two-piece): These toilets separate into tank and bowl for easier handling. The bowl alone weighs approximately 55 to 65 pounds -- manageable for one person. TOTO's installation documentation calls for standard 5/16-inch bolts and specifies checking that the flange is at or above floor level before setting the wax ring.

TOTO UltraMax II (one-piece): At roughly 99 pounds, this model benefits from two-person installation. The elongated footprint means the bolt holes are in the same standard location but the toilet is harder to maneuver over the bolts. Lay the toilet on its side to attach the wax ring, then stand it upright for final positioning.

TOTO Aquia IV (dual-flush, wall-hung version): The wall-hung Aquia IV uses a carrier frame and does not use closet bolts at all -- it attaches to the carrier frame bolts. The floor-mounted version of the Aquia IV uses standard closet bolts like any other floor-mount toilet.

American Standard Champion 4 and Cadet 3: These have a wider footprint at the base. The Champion 4 in particular has a very wide trapway and a heavier base. Standard bolt placement applies, but verify the rough-in distance (most Champion 4 models are 12-inch rough-in, but confirm with the model number).

Kohler Cimarron and Highline: Standard installation. Kohler sells a genuine accessory kit (K-GP85160) that includes closet bolts with their toilets in some packages, but third-party stainless kits are fully compatible.

Woodbridge T-0001: This one-piece unit is heavy (approximately 105 pounds) and has a skirted trapway that means the bolt caps may not be visible from the standard angle. Some Woodbridge installations use a concealed bolt cover panel. Confirm bolt access points before beginning.

Swiss Madison Sublime and Sublime II: Skirted one-piece design with concealed trapway. Swiss Madison provides specific installation hardware with some models, including a wrench-access cutout in the skirt. Confirm before purchasing a generic bolt kit.

For information about which toilet might be the right fit for your bathroom, see our guide to the best flushing toilets and our comparison of toilet rough-in sizes. If you are also replacing the flange as part of this project, our guide to closet flange repair and replacement covers that process in detail. For issues with leaks at the base, see our toilet leaking at base troubleshooting guide.

What about offset flanges and specialty installations?

An offset flange -- used when the drain pipe does not align with the desired toilet position -- shifts the toilet center by 1/2 inch to 2 inches relative to the drain. The closet bolt slots in an offset flange are in the same relative position to the flange ring, so standard 5/16-inch bolts still apply. However, offset flanges reduce effective flushing performance because the drain alignment is compromised. This is not a bolt issue, but a setup worth noting if you are combining an offset flange with a high-performance toilet like the TOTO Drake II or American Standard Champion 4.

Very thick tile floors -- particularly stone tile installations that add 3/4 inch or more to the floor level above the original flange -- require either long closet bolts (3-1/2 to 4 inches) or a flange extender kit. Flange extenders stack above the existing flange to bring the flange face up to or above the new floor level. Without bringing the flange up, the wax ring cannot create an adequate seal and the bolt length may be insufficient to engage enough thread for the nut.

Closet bolt torque and how tight is tight enough

There is no universally published torque specification for toilet closet bolts in the same way there is for engine head bolts, because the correct tension depends heavily on the toilet base material thickness, the floor condition, and whether floor shims are in use. The practical guidance from plumbing professionals and major manufacturer installation sheets consistently points to the same approach: hand-tight plus one-quarter turn, with the toilet showing zero rocking motion.

If you use a torque wrench for peace of mind, values cited in professional plumbing forums range from 5 to 15 foot-pounds for the toilet base nuts -- with the lower end being appropriate for thin porcelain and the higher end appropriate for thick commercial porcelain. Most residential installs fall in the 5 to 10 foot-pound range. When in doubt, err low and check for toilet movement rather than adding more torque.