I have a strange problem that has just started on one of my toilets. It
is located on the first floor of my house has it's own stand pipe. When
the toilet is flushed, the siphon action is too strong. At the end of
the flush, there is next to no water left in the trap in the bowl. This
is soon followed by some air gurgling back into the bowl.

I've checked the access panel of the stand pipe and water is draining
down it. It does not appear to be any faster than usual.

I don't think it is a blockage and there are no apparent water leaks.

My downstairs toilet is fine, but it uses it's own stand pipe. The
drainage for the sink and bath end up in the same stand pipe as the
"faulty" toilet and they are draining just as quickly as always.

Could this be an air leak in the pan connector?

Any help is appreciated.

~S~