Backflow Preventer Questions
Hi guys. I'm wondering if you guys could answer some questions about backflow preventers for me. I'm not an irrigation guy, and this is actually related to volunteer efforts on my part to try to solve a mystery for a local municipality. They are getting fecal coliform contamination in a well at their athletic complex as an ongoing problem. The well provides water for their snack bar and water fountains as well as their irrigation system. It's a drilled bedrock well, so I think it unlikely that the groundwater in the area is contaminated, although it is posslbe.
Possible sources of the contamination that I have identified are:
1) Surface water leaking into the well head (someone is inspecting the well for me today to let me know if it's flush with grade or elevated)
2) A bad well seal around the well casing allowing water to flow around the outside of the casing, and
3) Possible backflow from their irrigation system
This field does get a lot of geese on it, and I'm thinking that perhaps they're getting backflow from the irrigation system into the well. So what exactly is a backflow preventer? Is it like a check valve? Do they fail sometimes (I would imagine so)? How does one typically test one? Is there usually just one on a system or multiple?
I have no idea what their irrigation setup is and it's not likely I'll have that information readily available. I guess I just want to know a little more about backflow preventers and if it's possible that a failed one (or lack of one for that matter) could be causing surface water to flow back into the well.
Thanks in advance.