I have a 20 year old house which we have lived in for 5 years. For the first 4 or so years we had no plumbing venting problems......THEN.....I replaced all the toilets with Elger Titan toilets(6 litre flush).....great toilets by the way.....only have to flush those babies once.
Now I have two bathrooms that suck the traps dry! One in a shower 3 feet from the toilet and the other a vanity about 4 feet from the toilet.
What gives? Do those new toilets flush so well that they create a vacuum and pull the water out of those other traps? Nothing else was changed.
I went up on the roof and ran water down the vents and they pass water with no problem......any other ideas???
NOTHING, especially a toilet, can pull the seal from a properly vented lavatory trap. IF that is happening, then you have some other problem which we cannot diagnose without being there and seeing when and how it happens and how to cure it.
I was sure that after reading the forum for awhile that someone would be able to figure this out.