If You think backflow does not affect you, ask your self a couple questions.Do you have a pool, sprinkler system, water softener? These are 3 very common luxuries that very often require residential backflow...
If you see this in the field, please don’t test it. This is a serious problem that will cause problems for everybody that touches it. So, advise the client that this needs to be corrected.
Don’t Do It. Don’t open up any watts LF009 or variety of models of the 009 that are being used for Hot Water with out a complete Check Valve on hand.