Hi, our office has a Sloan toilet flash valve like the one shown at
http://www.sloanvalve.com/index_2240_ENU_HTML.htm. The valve sits on a
standard toilet.

Recently it started to leak at the top of the vacuum breaker flush
connector where it meets the vacuum breaker coupling. The leak happens
when the flush is just ending. Some water will leak out from under the
vacuum breaker coupling and it stops leaking when the flush ends.

Anyone knows how to fix it? Is it just a loose coupling, or is
something wrong inside?

The fixture is about 3 years old.

Thanks