plumbing stack issues?

BlueBSH

Attached is a crude diagram of the plumbing layout for 1/3rd our house...

I say 1/3rd because there is three seperate sections of sanitary line that eventurally merge underground into one large line... this section is the one I am wondering about, each of the three sections have their own 1.5" soil stack with a proper vent on the roof

in this section, when you flush the toilet you hear the mini vent they put on under the sinks rattle as it tries to draw in air to counter act suction caused by the flush...

the stack is upstream from the toilet, any reason this would be caused? there is only one connection to the stack from what appears to be the 2nd to highest point in the line... to explain the diagram here is how the system goes right now


3" PVC riser pipe comes out of the slab goes up to the ceiling then does a 90 degree turn to go another direction with a Y branch that goes to the first toilet also, first it hits a T that T's off to a 1.5" line for the sinks, this is the sinks that have the mini vent on... then another T to a 1.5" line to the main bath/shower the other 3" of the T continues to a 3" T that has a U trap on it for a walk in shower, after that another 3" T with no trap, goes up to the toilet, 3" line continues and branches off to a 1.5" line that continues to a T that goes vertically to the stack vent, the othe end terminates at the last sink...

I'm sure I messed up the description since there is so many T's

but should there be more venting? I was reading plumbing code and it says all fixtures must have vents, what exactly does that mean? the diagram they show has basically a connection from every fixture back to the stack vent pipe this was definatlly not done that way

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