To close the loop with the check valve issue I was having - I returned the two new, leaking ones to the vendor I purchased them from, and I was refunded the cost of the items as well as the shipping. I asked the vendor to check their inventory for a systemic or supplier problem with these valves, but they’ve “sold 99 of these since acquiring _________ in the last year, year-and-a-half, and have only had two returns”. So, buyer beware - definitely bench test before installing.
I ordered a third check valve, from a different vendor, and that one checked out good, right out of the box. This vendor acknowledged past issues with these and is now making them in house.
RobY