Cracked Toilet Cistern — Repair or Replace?
Check the steps below first — if you're not confident, get it fixed safely today.
Post a job — we'll find you an engineer →A cracked cistern that leaks onto the floor near the toilet can cause water damage to the subfloor over time. Identify the crack location carefully before deciding on repair vs replacement.
A cracked toilet cistern is usually not repairable in the long term — ceramic does not reliably bond back together under water pressure. The practical options are: temporary repair with epoxy for minor surface cracks, or replacement of the cistern (or whole toilet suite if a matching cistern is unavailable).
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Most likely cause & what to check
Turn off the water supply and flush to empty the cistern. Dry the inside of the cistern completely with towels and allow to air dry for several hours — the crack must be completely dry for any repair product to bond.
Identify the crack — is it internal, external, or through both walls? A hairline crack on the outer surface may be stable; a crack through the cistern wall will leak under pressure and cannot be reliably sealed long-term.
For a hairline surface crack as a temporary measure: clean with isopropyl alcohol, apply waterproof epoxy putty or two-part epoxy adhesive, smooth flush with the surface, and allow to cure for 24 hours before refilling.
Accept that any repair is temporary — cistern ceramic cannot be permanently fixed once cracked through. Plan for a replacement within 6–12 months.
To replace the cistern only, you need to match the exact model to ensure the bolt holes and flush valve connection align with the existing toilet pan. Search for your toilet manufacturer and model number to find a replacement cistern.
If a matching cistern is unavailable (common for toilets over 10 years old), replacing the full toilet suite is usually the most practical option. A complete close-coupled toilet suite costs £80–250.
A plumber can replace a toilet in 1.5–2 hours. If you are comfortable with basic plumbing, replacing a toilet is a DIY-achievable task using push-fit connectors for the soil pipe connection.
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