I am doing my bathroom removed the tub and putting recess shower tray . I have two bathrooms next to each other. bathroom one drains comes in bathroom two and then goes in soil pipe as soil pipe is boxed in bathroom 2 corner. check
picture 1 and 2
I added boss connector to soil pipe which is about 45 cm below the roof to drain both bathroom separately. used 40mm pipe.
check picture 3 and 4
The drain pipe of shower tray is running around 1meter before turning 90 degree downwards parallel to the soil pipe and connected to the soil at around 40 cm below.
my concern is siphon of the pipe when they drop 90 degree downwards. please let me know if I need to vent there 40 mm pipes .