Hi Kristi,

What is a pvb? Sorry for the daq. Aloha

kristi08, I am guessing that you mean 'pressure vacuum breaker'. My understanding of how the device works is that it prevents water from 'siphoning' back into the house system when the pressure in the house system drops lower than the exterior (hose or irrigation) system. So when the toilet is flushed or the washing machine is filling, the pressure at the hose bib drops, and the water in the exterior system would flow backwards (because the exterior pressure is now higher) and contaminate the house system. The vacuum breaker kicks in and this flow gushes out on the ground. It ought to stop when the pressure equalises or when the exterior system is empty, whichever occurs first.
If it continues, then either I do not understand the problem or something else is going on.

ronalawn- I am also guessing that it stands for pressure vacuum breaker-- it is the piece that the water cirulates through after it flows to the exterior of the house- I was told it was more like a pump that increases pressure to the system. Your explanation about the backflow contaminating the system sounds right-- I never had this problem with my last pvb(which cracked last winter)-- It was a nice metal version-- this is a plastic one that looks cheap. I have always run into the basement and shut the main water off when it gushes because I don't want to flood the side of the house-- I guess i will have the plumber come in and see if he can install something that will prevent that hose bib from drawing back into the house. Thanks so much for your explanation-- just feel like I'm dealing with "guys" who are novice and took the $ and don't know how to make the system function properly.