Failed antivac trap?

[CountryFan]

It’s been a while since I’ve done plumbing and never really worked on pedestal traps (other than my own).

The problem:

For a while my basin has been slow to drain, I’ve tried a couple of attempts at clearing, including using my wet vac, but it’s still a little slow. The trap is a McAlpine pedestal trap X10v or similar. I’ve had the trap off today and it was practically clear, using plunger offers no resistance either. The self-sealing/anti-vac part seems ok, but I used to be able to hear it, now I don’t.

Questions:

Does this point to a failed trap or at least the antivac part of it? I can’t seem to locate spares for it. Cba replacing with a P-trap and waterless traps are dearer, although the Viva one seems ok price wise - anyone used Viva and are they ok?

Do I actually need an antivac trap? I can’t remember why I asked for it, think it was because the shower used to gurgle or something. Shower possibly tees into bath waste (shower is en-suite, bathroom next door) trouble basin is en-suite

 

[Hugh Jaleak]

Slow draining points to blocked pipework. Unlikely to be an issue with the trap IMO. Anti Vac traps are needed where the waste run risks siphoning the trap, so allows air behind the water to prevent the trap being pulled following a discharge.

 

[CountryFan]

Slow draining points to blocked pipework. Unlikely to be an issue with the trap IMO. Anti Vac traps are needed where the waste run risks siphoning the trap, so allows air behind the water to prevent the trap being pulled following a discharge.

Ok,I’ll try downstream of the trap and see if it’s anything to do with that. It crossed my mind if it was that but the basin filled quite quickly even after trap removal.