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Likely cause: a partial clog in the toilet trap
If the tank parts check out and only this toilet is weak, something may be lodged in the trap. Try a flanged plunger.
Why this happens
HomeTips lists a partial clog in the trap among the causes of a weak flush, and recommends plunging with a flanged plunger. A clog that lets water through slowly still robs the flush of its pull. HomeTips also notes that some aging low-flow toilet designs simply flush weakly.
How to fix it
- Use a flanged plunger, the kind with a soft extension at the bottom, so it seals in the bowl outlet.
- Plunge firmly several times, then flush to test.
- Repeat once or twice if the flush improves but is not fully back.
- Do not pour drain chemicals into the toilet before calling for help, and tell the plumber if you already did.
When to stop. If plunging does not help, or the weak flush keeps coming back, call a plumber.
If this does not fix it, tell the plumber
- Only this toilet flushes weakly, and the tank parts check out.
- Whether plunging helped.
- Whether any drain chemicals went into the bowl.
Build the full list: what to tell the plumber.
Start this troubleshooter over
References (every fact above comes from one of these pages)
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