网上查了下这个问题很普遍,然后他们自己做:You can go to a 4" pvc sch 40.
-demons(堂·吉诃德);
2017-10-18{207}(#11121977@0)
Take some stainless steel screen and wrap it in a 2" tube. Wrap it with more screen until it fits snug in the 4". Glue the other 2" reducer on it. Make it as long as possible. Should be an instant glasspack.