Quick Answer:
After turning water back on following winterization, a toilet that briefly refills or runs is often caused by rubber parts that stiffened or warped in the cold. Start by inspecting the flapper and its seat for stiffness, hardening, or warping. If the flapper is rigid or no longer seals cleanly, replace it — that usually fixes the problem quickly and cheaply.
Why This Happens
Cold temperatures make rubber less flexible. When a toilet sat in an unheated space or was drained for winter, the flapper and other rubber seals can become hard, misshapen, or cracked. When you restore water pressure, a stiff or warped flapper may not seal immediately, letting water leak from the tank into the bowl. The tank then partially refills, which looks like a short, unexplained refill.
Other contributors can be a sticky flush lever, a chain that catches, or a valve seat with mineral deposits. If you recently had any changes to your supply pressure, that can also trigger similar symptoms — see Phantom flush after pressure change. If the tank refills at odd hours or you notice slow fills overnight, check the guide on Toilet refills only at night for more causes.
Step-by-Step What to Do
1. Turn off the water and drain the tank
- Shut the shutoff valve at the wall behind the toilet.
- Flush to empty most of the water from the tank. Use a sponge to remove remaining water so you can inspect parts dry.
2. Inspect the flapper
- Look for cracking, flattening, or hardening. Press the flapper with your finger — it should bend easily and spring back.
- If it feels stiff, brittle, or stays warped, plan to replace it.
3. Check the flapper seat and chain
- Examine the rubber seat around the flush valve for mineral buildup or rough spots; clean with a soft cloth if needed.
- Make sure the chain has a little slack (about 1⁄2 inch) and does not bind under the flapper when it settles.
4. Test the flush lever and hinge
- Move the flush lever by hand to confirm smooth operation and that it returns to rest position without catching.
- Replace or lubricate the lever if it’s sticking (use silicone-safe products only where appropriate).
5. Replace a stiff or warped flapper
- Buy a matching flapper at a hardware store — most are inexpensive and easy to install.
- Follow the package instructions: remove the old flapper from the pegs or ring, attach the new one, and adjust chain length.
6. Refill and observe
- Turn the water back on slowly and let the tank fill. Watch for continued slow leaking into the bowl or repeated refills.
- If the problem stops, run a few test flushes to verify the fix.
What Not to Do
- Don’t expect cold-stiff rubber to recover; plumber if replacement is needed.
- Don’t pour boiling water into the tank or bowl to try to reshape parts — rapid temperature changes can crack porcelain and damage seals.
- Don’t rely on temporary fixes like shims or bulky tape under the flapper; they usually fail and can make the seal worse.
When to Call a Professional
- If the flapper seat is damaged, cracked, or the tank rim around the valve is chipped.
- If replacing the flapper doesn’t stop the leak or the toilet continuously refills.
- If you’re uncomfortable working on the tank, or if there are signs of a larger problem (cracked tank, persistent high water bills, or supply-line issues).
Safety Notes
- Turn off the shutoff valve and drain the tank before working inside to avoid unexpected water flow.
- Wear gloves when handling old rubber parts and when cleaning mineral deposits.
- Avoid harsh chemical cleaners in the tank; they can accelerate rubber deterioration.
Common Homeowner Questions
- How long does a flapper last? Typically 3–5 years; colder conditions can shorten that life.
- Can I reuse the old flapper if it looks fine? If it flexes easily and seals cleanly, yes — but replace it if it feels stiff or warped.
- Will a small leak around the flapper raise my water bill quickly? A steady small leak can add up over weeks; fix it promptly to avoid higher bills.