Commercial restroom toilet flushes by itself every few minutes

The faint trickle into the bowl makes a flapper or flush-valve-seat leak the leading suspect. A useful confirmation is to add a few drops of food coloring to the tank water, then wait without flushing. If colored water appears in the bowl, water is bypassing the flapper or the seat. Clean the seat and check for mineral buildup, warping, or a damaged hinge area before installing the replacement.

The supply-shutoff test is also useful, but interpret it carefully. With the supply closed and the tank marked, a falling tank level confirms a tank-to-bowl leak. If the level instead rises while the supply is on and reaches the overflow tube, the fill valve isn’t shutting off or is adjusted incorrectly. A loose handle or chain usually causes a partial flush or prevents the flapper from seating, so check that the chain has slight slack and isn’t catching under the flapper. On a commercial fixture, use the correct flapper or flush-valve seal for that model rather than assuming a universal part will hold up.

For commercial restrooms, match the replacement flapper or seal to the fixture’s flush-valve design rather than relying on a universal part. Hard-water deposits can roughen or distort the seat, and some commercial bowl or tank cleaners can shorten the life of certain rubber compounds. If a correctly sized replacement starts leaking again quickly, inspect the seat and consider a manufacturer-approved seal instead of repeatedly replacing generic flappers.

Check the tank water level against the overflow tube after refill. If it reaches or spills into the tube, the fill valve is misadjusted or failing, which can cause periodic refills and a trickle into the bowl.

Also make sure the handle returns fully and the chain has slight slack. A binding handle, overtightened mounting nut, or taut chain can keep the flapper from seating completely.

If the marked tank level drops with the supply shut off, tank water is escaping; check for an external leak before concluding it’s entering the bowl. If the water is going into the bowl, that won’t tell you whether the flapper is the culprit or the flush-valve seat is damaged. I’d inspect the seat before choosing a replacement; otherwise, even the right-sized new flapper may not seal against a rough or distorted surface.

The tank-level and overflow checks already discussed are the relevant starting point for this tank-type fixture. I wouldn’t use bowl water level alone to choose a flapper or fill-valve repair. The follow-up should establish where tank water is going, including ruling out an external leak, before replacing parts.

I’d consider replacing the flush-valve assembly if its seat or body is visibly damaged, or if a correctly matched seal still leaks after the seat and linkage are checked; repeated seal swaps against a bad surface are unlikely to be a lasting fix. A compliance inspection is a separate question: age or phantom flushing alone doesn’t establish noncompliance. If there’s a specific concern about required fixture type, accessibility, or local plumbing rules, have the responsible facilities person or local authority assess it rather than assuming a tank repair answers that question.

Colored water in the bowl shows that tank water is reaching it, but it doesn’t by itself prove a flapper or seat leak. If the tank is overfilling, colored water can also enter the bowl through the overflow tube. Check the tank level against the overflow before treating the dye result as confirmation of a leaking seal.