Gurgling waste

[Lawrence]

Is there another way of solving a gurgling basin waste without fitting an air inlet valve?

I only have access to about a 200mm length of waste pipe (sloping at 1 in 40) that joins the trap to a vertical section of waste pipe which is concealed behind a wall. If the air inlet valve is the only / best way to resolve this problem can it be fitted on the 200mm section of pipe from the trap to the vertical pipe?

thanks

[rosebery]

Two options:

a. In line anti vac device.

b. Anti-syphon trap.

Cheers