The vent is there to vent the drain to atmosphere, you would need to check with BC to see if you can do what you are asking, Air admittance valves only let air in, the vent allows gases to escape as well, why do you need to shorten it
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local