The bowl in one of my commodes fills up to it's normal line, but the water in the bowl gets lower in about 30 minutes. The tank is filling up fine. I replaced the flapper, but the problem continues. Any suggestions. Thank You. AY
Look for a clogged vent associated with that toilet. A partial vacuum may be being created when other devices drain, which is sucking the water out of that toilet through it's trap.
Try flushing other toilets and running water in sinks while someone watches the affected toilet's bowl level. That may give you a clue.
Jeff
And if it still drains out slowly when no other fixtures have been used, there may be a flaw in the bowl passage, allowing leakage to the drain or even leaking into the floor.
Much less likely, a string or similar is stuck in the bowl outlet and is "siphoning" water out along the string.
Jim
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