anti-syphon

Hi, I replaced our trap with an anti-syphon one (and also changed the angle of the washing machine waste). But when the washing machine starts, it still gurgles. Why does that still happen, and more importantly, what else do I need to do? Please see 2 images before/after: Thanks in advance!

I've just got a 40mm anti syphon p trap to replace a normal sink u-bend (to fix gurgling sink issues). The upright part that should connect to the sink waste is 40mm, but as the sink waste is also 40mm there's no way for them to slot together. At the other end, the p trap is large enough to...