How do I know what size toilet seal to buy?

Determining the size of a toilet seal involves two core measurements: the diameter of the toilet drain outlet and the distance from the center of the bottom mounting hole to the wall (center-to-center distance). Combine these measurements with the seal type selection for a clear, tool-free process. Follow these steps:

I. Core Measurements: 2 Essential Dimensions (Mandatory)

1. Measure the toilet drain opening diameter (most critical)

The toilet drain opening is the circular hole at the bottom connecting to the pipe, determining the seal's “inner diameter compatibility”:

Method: Remove the old seal (if present). Use a tape measure/ruler to measure the inner diameter of the drain opening (measure from the inner edges of the opening, not the outer edges).

Common Sizes: Household toilet drain openings primarily come in two sizes:

Standard Size: 110mm (4.33 inches) (fits most household toilets);

Small Size: 90mm (3.54 inches) (used in some older or niche toilet models).

Note: If glaze protrudes, measure the “actual water passage diameter” to avoid overestimating glaze thickness.

2. Measure the Pit Distance (to confirm compatibility and prevent installation misalignment)

Pit distance is the distance from the center of the toilet mounting hole to the wall surface (after tiling). While it doesn't directly determine gasket size, it affects the gasket's “installation depth” and compatibility:

Method: Use a tape measure from the wall surface (tiled surface, not waterproof layer or bare wall) to the center of the toilet's bottom mounting bolt holes (typically two bolt holes; take the midpoint).

Common sizes: Residential c-flush distances are mainly 300mm (small units/older homes) or 400mm (mainstream new homes). Some special layouts have 200mm, 250mm, etc.

Purpose: Incorrect measurement may cause misalignment between the toilet drain outlet and the pipe after installation, leading to leaks even with correctly sized gaskets. Therefore, simultaneous verification is essential.

II. Supplementary: Confirming Gaskets Type (Details Affecting Size Selection)

Toilet gaskets are categorized into 3 types based on installation method, each with varying “compatibility” with dimensions. Select based on the existing gasket or toilet structure:

III. Practical Steps Summary (5-Minute Fix)

1. Turn off toilet water supply, empty tank and bowl water, disconnect inlet hose;

2. Unscrew bolts under toilet base, gently slide toilet away (use cloth to prevent tile scratches);

3. Remove old seal (if stuck, gently pry with screwdriver and clean residue);

Measure the drain outlet diameter (record value, e.g., 110mm) and center-to-center distance (record value, e.g., 300mm);

Select a gasket based on drain diameter: 110mm uses standard size, 90mm uses small size, or choose “90-110mm universal” if unsure;

When purchasing, inform the seller of the “drain outlet diameter + center-to-center distance.” The seller can assist in confirmation (e.g., for a toilet with a 300mm center-to-center distance, ensure the seal ring length does not interfere with pipe alignment).

IV. Pitfall Avoidance Tips

Don't rely solely on toilet brand/model: Even identical models across brands may have different drain outlet sizes—actual measurement is most accurate.

Seal material: Prioritize silicone (heat-resistant, excellent odor-proofing) or rubber (high cost-effectiveness); avoid low-grade plastic (prone to aging and leaks).

Installation Notes: Ensure the seal is fully seated over the drain outlet without wrinkles. After reinstalling the toilet, press evenly around the rim to guarantee a tight seal.

Following these measurement steps ensures a 99% success rate for selecting the correct size for household toilets. If uncertainty persists after measurement, take photos of the drain outlet and toilet base structure and consult the merchant's customer service.