Those elbows and reducers are ridiculous .. in my opinion it should of been connected with more care to air flow, elbows and reducers by their nature cause large amounts of restriction.
If it was piped by a *talented* person you would not see such a contraption of fittings.
talented workers are far and few between , even when safety is a factor you often end up with monkeys doing the Job..
quote:
Every PVC fitting has an airflow resistance that is approximately equal to the footage given in the table below. For example each 4" 90 degree sweep elbow adds the equivalent of 6 feet of straight pipe resistance while a 4" 90 degree sharp edged elbow adds 15 feet of equivalent straight pipe resistance
Pipe size restriction
4 inch Reducer cause the the vent to perform as if it is 30 ft longer
6 inch reducer causes the pipe to perform as if it is 60 ft longer
How to measure airflow in PVC piping requires careful measuring of airflow with a pitot tube or calibrtated anenometer to determine CFM