Adding to Vent Pipe

[cpowers]

Attached is a somewhat simplified diagram of my dvw system. This is a 100+ year old house, with some pretty hacked up plumbing. The downstairs 2 sinks i added AIV's to several years ago, to help with good flow. Currently everything drains and works perfect. Last year i replaced 2 old toilets with Cadet 3's. Since then, When the upstairs toilet flushes, the downstairs toilet (sometimes) will gurgle. It seems pretty obvious that the new high flow toilet is creating a positive pressure in the system.

I am looking to fix this the easiest way possible that is (reasonably) correct. The red pipe in my picture is what i am thinking of adding to the system to provide a path for that positive air pressure.

Any thoughts/comments are appreciated.

 

[Terry]

The AAV's on the lower end do nothing to help when water surges down the line toward them. They pull air, but don't allow displacement of air.

The lower plumbing would be less affected by venting on the toilet trap arm. Any vent you bring up should go up through the roof, not tying back to a waste stack. I've noticed the same thing on homes before, the water sloshing around in the bowl below when the upper bowl gets flushed. Some people live with it.

And you do have AAV's on all the fixture below right? Otherwise they wouldn't be vented.

 

[Sponsor]

 

[cpowers]

I put the AAVs in to allow venting, because they basically weren't, just the two sinks, the distance from the tub and dishwasher is very small.

 

[Reach4]

The traps on all of your sinks and tub are S-traps. Not good. Look that up.

There are other considerations, but start there.

 

[cpowers]

no, that is just my lazy drain modeling skills

 

[cpowers]

Would i be better served, by leaving the current 'vent stack' and replumbing the upstairs restroom and washing machine with it's own waste line?

Thanks!
Chris

 

[Terry]

Would i be better served, by leaving the current 'vent stack' and replumbing the upstairs restroom and washing machine with it's own waste line?

Thanks!
Chris

And connecting downstream of the downstairs toilet.