Quick Answer:
If a toilet started doing a phantom flush after a remodel, vibration or movement during work often changed the flush chain length or the flapper position. The quickest fix is to check the chain and adjust the slack so the flapper can sit fully on the seat. If the flapper or seat is damaged and won’t seal, call a plumber.
Why This Happens
During remodeling, tools, cabinets or people bumping the toilet tank or handle can shift the lever, chain or flapper. A chain that is too tight can lift the flapper slightly, and a chain that is too loose can get caught under the flapper. Either problem lets water trickle past the flapper and the fill valve reopens briefly, creating what looks like a random flush.
If work involved shutting and turning water back on, the refill valve may also be settling into a new position, which can cause similar symptoms—see Phantom flush after turning water back on for related causes and checks.
Step-by-Step What to Do
1. Observe one full cycle
- Flush and watch the flapper as the tank empties and refills. Note whether the flapper drops flat onto the seat and stays there.
- Check whether the refill tube is hitting the overflow pipe or if water level is set too high; excess water can cause intermittent refilling.
2. Check chain routing and length
- Lift the tank lid and trace the chain from the handle lever to the flapper. Make sure it isn’t twisted, caught under the flapper, or looping around other parts.
- There should be a small amount of slack—enough so the flapper can close fully but not so long it droops under the flapper. Aim for about 1/2 inch of free play when the flapper is closed.
3. Adjust chain slack
- Unhook the chain from the lever or move it to a different hole on the lever arm to increase or decrease length. Some chains have extra links you can remove.
- After each small adjustment, flush to confirm the flapper seats properly and the fill stops when the tank is full.
4. Inspect flapper and seat
- Look for warping, mineral buildup, or torn rubber on the flapper and uneven wear on the seat. Clean gently with a cloth and mild cleaner if needed.
- If the flapper or seat looks damaged, replacing the flapper is inexpensive and often solves phantom leaks.
5. Final checks
- Make sure the handle isn’t loose or sticking; a wobbly handle can change chain tension intermittently.
- If you recently installed a filter or changed supply parts and see odd refilling behavior, also check related parts and consider the advice in Random refills after installing filter.
What Not to Do
- Don’t tighten the chain so much that the flapper cannot close fully—this can prevent a proper seal and make things worse.
- Don’t jam or wedge the flapper closed with foreign objects or glue to stop a leak.
- Don’t delay contacting a professional if the flapper won’t seat even after sensible adjustments; continuing to run a leaking toilet wastes water and can hide other problems.
When to Call a Professional
- If the flapper or seat is damaged or warped and a replacement doesn’t stop the phantom flushing.
- If you suspect the fill valve or internal tank parts were damaged during the remodel, or the toilet repeatedly refills despite adjusting chain and replacing the flapper.
- If the leak is large, continuous, or you can’t access parts safely in the tank.
Safety Notes
- Turn off the water only if you need to replace parts and are comfortable doing the job; most chain adjustments can be done with the water on because the tank handles the water flow.
- Wear gloves when reaching into the tank to avoid skin contact with mineral deposits or cleaners.
- Avoid using harsh chemicals inside the tank; they can damage rubber parts and make sealing problems worse.
Common Homeowner Questions
- Why does my toilet randomly refill? Usually a flapper that isn’t sealing or a fill valve reset; check chain slack and flapper condition first.
- How much chain slack is right? Enough so the flapper can sit fully on the seat with about 1/2 inch of free play.
- Can I fix this myself after a remodel? Yes, chain adjustments and flapper replacements are common DIY fixes; call a plumber if parts are damaged or the problem persists.