"Kohler tank parts" covers everything in or attached to the tank that isn't the flush valve, fill valve, or flapper — the tank-to-bowl gasket and brass bolts (the seal between tank and bowl on two-piece toilets), the sponge gasket (a foam ring inside the tank), and the tank lid itself. Tank-to-bowl gasket failures are the second-most-common Kohler repair after flapper replacement.
Tank-to-bowl gasket — the most common tank-side failure
Between the tank and the bowl sits a circular rubber-and-foam gasket (sometimes called a "sponge gasket" or "spud washer") that seals the water connection. Over 10–15 years, the rubber hardens and the foam compresses. Water leaks at the tank-to-bowl junction — usually a slow drip you'll see on the bowl's lower-rear surface or pooling on the floor behind the toilet.
Tank-to-bowl repair kit
- Universal kit: Korky 481BP — $12–$18. Includes new gasket, two brass tank bolts, two rubber washers, two metal washers. Fits Kohler, TOTO, American Standard, Mansfield, Gerber — virtually all US two-piece toilets.
- Kohler-specific kit: Kohler GP1059291 — $25. Slightly higher quality rubber, identical mounting pattern.
- Heavy-duty option: Fluidmaster Universal Performax — $20. Better long-term seal for hard-water areas.
How to replace the tank-to-bowl gasket (45 minutes)
- Shut off water at the wall. Flush and sponge tank dry.
- Disconnect the supply line at the tank.
- Inside the tank, unscrew the two brass bolts holding the tank to the bowl. Use a flathead screwdriver from inside the tank to hold the bolt head while loosening the nut underneath with a wrench. (Tip: brass bolts often seize — use penetrating oil overnight first if they won't budge.)
- Lift the tank straight up off the bowl. Set the tank on a soft surface (towel-padded floor).
- Remove the old gasket from the bowl-side flange or the underside of the tank (it sticks to whichever surface is harder).
- Clean both surfaces — the bowl-side rim where the tank sits, and the tank-side outlet flange. Wipe with vinegar to remove mineral residue.
- Install the new gasket on the bowl-side rim (or the tank-side flange — manufacturer-specific; check the kit instructions).
- Insert the new brass bolts through the tank from inside, with the rubber washer between bolt head and tank.
- Carefully lower the tank back onto the bowl. The bolts should slide through the bowl-side mounting holes.
- From below the bowl, install metal washers and nuts. Tighten alternately, hand-tight + 1/4 turn — never overtighten.
- Reconnect supply line. Turn water on. Check for leaks at the tank-bolt nuts, the gasket joint, and the supply connection.
Tank lid replacement — the sourcing puzzle
Cracked tank lid is a common Kohler problem — usually from being knocked over during cleaning, or a falling decoration. Replacement is straightforward when the model is current; tricky when it's been discontinued. The two paths:
Path 1: Current production Kohler — easy
If your Kohler is currently in production, the tank lid is available direct from Kohler Customer Service. You'll need the model number (printed on the underside of the existing lid or on the inside of the tank) and the color code (printed near the model number — e.g., "0" for White, "96" for Biscuit, "47" for Almond). Tank lid order takes 5–10 business days, costs $80–$220 depending on size and color.
Path 2: Discontinued model — harder
For older Kohlers (pre-2010 designer lines, discontinued colors), the path is one of:
- eBay or Replacements.com — broken Kohler tanks are often parted out; a matching used lid in your color may be available.
- Lid Pros / This Old Toilet — specialty US suppliers that stock discontinued Kohler tank lids. Search by Kohler model number.
- Kohler dealer special order — sometimes Kohler can custom-make a lid for a discontinued model, with 6–10 week lead time and $300+ pricing.
- Repair (cosmetic) — for hairline cracks, a porcelain-bonding epoxy can extend the lid's life. Not ideal but cheaper than replacement.
Sponge gasket (internal water deflector)
Inside the tank, a foam ring sits around the flush valve overflow tube. Its purpose is to direct refill water downward and reduce splashing. Over time, the foam compresses and the deflection becomes less effective — usually noticed as splashing sounds during refill. Replacement is a $5 foam ring, slides on/off the overflow tube without tools.
Tank bolts — the brass kit
The brass bolts that hold the tank to the bowl will eventually corrode in chlorine-treated water, especially in homes with chlorine tablets dropped in the tank (a common cause of accelerated corrosion). Replace the bolts when you replace the gasket — it's the same kit. Never reuse 10+ year old brass bolts; they can shear during retightening.
Cost summary
- Tank-to-bowl gasket kit (universal): $12–$25
- Tank-to-bowl gasket kit (Kohler OEM): $25
- Brass tank bolts (replacement only): $5–$8 set
- Sponge gasket: $5
- Tank lid (current production): $80–$220
- Tank lid (discontinued, sourced): $150–$450
- Time DIY for gasket replacement: 45–60 minutes
- Plumber service call (gasket): $200–$320