"dpb" wrote
cshenk wrote:

I'm thinking vacumn pulling via vent sounds most likely just now but I'll
have her give it another good go with a plunger and change out the
flapper since those are simple cheap fixes.
...

I'd also suggest a good dose of vinegar in the tank and a squirt of CLR or
similar in the ring area of the feeds--I'd still suspect liming there as a
culprit in low flow during flushing, particularly if water supply is a
little or a lot hard...

Grin, more info. It's not when flushing the toilet. Acts normal then.
Sporadically though, the bowl volume goes way down, sometimes coming back up
later on it's own. Flushing restores it always.

I suppose the changes enumerated _could_ have changed the venting and
caused a problem but I'd think it fairly unlikely--I don't think I've ever
known of a case that caused measurable/noticeable volume to go down the
drain on a consistent basis. That would imply somehow having a persistent
vacuum problem which doesn't seem too likely to be caused by wind or other
changes of the type you've noted as that would be variable.

I'm wondering if it's a combination thing?

Easy enough to test (altho probably not for Mom) by adding a baffle at the
vent exit. Sister good at climbing too???? vbg

Sadly, Sister pretty much out of the picture. So's the brother. Life moved
on and she isnt part of their world anymore. I'm the only one with daily
communication. Unfortunate but happens.