Basepump Hi-Performance Water Powered Back-up Sump Pump with Atmospheric Vacuum Breaker HB1000AVB Most states and municipalities require that you protect the potable water supply from any possible cross contamination, whether it's likely to happen or not. These are connections that could cause potable water to be contacted by non-potable water, like sump water. All standard models of Basepump are designed to prevent that from happening, but some authorities require a separate "approved" device be installed to protect the water supply. In these cases, the solution has been to install either a dual check valve or a Reduced Pressure Zone (RPZ) device to accomplish this. The RPZ device will restrict water flow and in many cases prevent a water powered system from operating. It is expensive, requires an annual inspection by a certified technician using special equipment, and must be reported to the plumbing authority in your municipality. Most municipalities recognize Atmospheric Vacuum Breaker (AVB) devices. Other water powered backup sump pump designs cannot use them, but Basepump can. Because of its location on the ceiling, it has the necessary height to prevent water from backing into the potable water supply. It simply cannot happen if installed properly. Once installed, inspected, and approved there should be no further question about it's safety. This makes it possible to meet the codes and also keep the costs down. Always check with your local plumbing department if you have any questions. If you are not satisfied for any reason products may be returned within 30 days of shipment for a credit or exchange (provided the product is undamaged), except where noted, NOT RETURNABLE. Return documentation should clearly specify credit or exchange. Returned items must be in the original packaging. All returns must include a return authorization (RGA) number that can be obtained by contacting our Customer Service Department. Original shipping cost deducted. Reference to brand names and numbers are for reference only, and not meant to imply that they are made by that manufacturer (OEM). Sometimes images shown are generic and not meant to infer that they are actual. The parts will work as intended and are high quality and precision tested. Track Page Views With Auctiva's FREE Counter