Just wondering if anyone has a preference or a reason to use either a bell trap or a P trap for basement floor drains when they flow into a sand mound. It is for a house being newly costructed in SW Pa. The plumber wants to use the bell trap as is normally done, but the contractor installing the sand mound recommends the P trap, (something about the system “burping”). Is there a significant difference one way or the other? Running these drains into a separate holding tank or drywell is not an option. TIA Jeff