Sweetfilter is a newer style sewer vent filter design that resists freeze-up, allows condensation to drain inside the unit rather staining your roof like other "T" shaped designs, and eliminates sewer odor overnight. The atmosphere inside all operating plumbing vent stacks is soaking wet and 100% saturated with water. Do not be confused by anyone who tells you the inside of the stack is dry and must be protected from rain water. Its simply not correct! Sweetfilter is built with the same materials as your vent pipes, with no metal parts to corrode and includes our frost proof "easy to install" universal fit coupling. Oxpellet hydrophobic media prevents entry of odors, aerosolized pathogens, and VOC"s into your environment. Sweetfilter is shipped ready to slide over your vent stack. 90 day money back warranty, 5 year manufacturers warrantyFirst, all drain and sewage waste from your house flows into the sewer or septic yard tank. Secondly, as water flows into any drain, foul, corrosive, toxic gas laden, air is displaced and must be vented (H2S - hyrdogen sulfide and methyl mercaptans), or the water will not go down the drain. Many homes (especially mass produced houses) have been designed to minimize plumbing costs. One major efficiency is the use of branch venting for fixtures in close proximity. Although less expensive initially, it makes sewer odors far more common. The PEC Sweetfilter requires no special tools for installation and simply slides onto existing drain vent pipes on your roof with universal fitting included with your purchase. Sweetfilter works in any position, even upside down. Slide units over existing cold air roof vent stacks, yard vents, or "candy canes". Use screwdriver to rotate clamp screws clockwise evenly until secure against stack.Two of our best customers are Honolulu County, Hawaii and Juneau County, Alaska. Need we say more?