SINK NOT DRAINING DUE TO NO OVERFLOW

[mogwai]

Hello

We recently had a bathroom referb with a new sink and vanity unit that contained all new plumbing for it. The sink doesn't have an overflow and is draining really really slowly as I understand that there needs to be an air vent in the trap etc.. I know that this is pretty basic but know very little about plumbing but am asking if anyone could kindly point me in the right direction with regards to the parts that I'll need to get and install to rectify this issue. Pics attached.

Many thanks for any advice.

 

[ShaunCorbs]

Can’t you get the plumber back whose installer it ?

Adjustable Inlet Tubular Swivel Anti-Syphon 'P' Trap

75mm Water Seal Adjustable Inlet Tubular Swivel Anti-Syphon (Silentrap) 'P' Trap with Universal Outlet

mcalpineplumbing.com

11/4 eg asa

 

[MikeJhn]

Needs an air admittance valve.