My toilets don't flush everything down, even when holding down the handle. This is happening in all 5 toilets in the house. Actually it's the house that I work in. There's 3 stories. The offices are on the 2nd story with 3 toilets. The living quarters are on the 3rd floor (2 toilets). The housekeeper started using blue toilet cleaner recently (I guess what you put in the tank). Don't know if that has anything to do with it.

I'm not sure how they are vented. The maintenance man said there's 2 vents in the roof. We have a lot of oak trees around the house. Maybe a squirrel in the vent?

Wow! All five toilets acting the same way? If it were just one or two I would suspect mineral buildup in the jet,(have you checked?) but with all five I have to go with blocked vents. Do all of your vents revent back in the attic before exiting out the roof with one pipe? Waiting on your reply. Tom

Sounds to me like you have some revents in the attic to check along with checking foir dead critters in the roof vents. If this were just one or two toilets we could focus on those but when all toilets are affected we must take a hard look at the system that affects them all. Since you aren't complaining about drainage backups all that's left is the vents. Have them checked. Good luck, Tom