backflow preventer

I did some searching, and have identified these parts here in the video, you could see my issue that it’s been leaking. Seems to happen when the heat comes on or for hot water usage. Do I simply replace these two parts in problem fixed? Or is there a problem elsewhere?

I have a Febco 850 backflow preventer unit. Water sprays out under the cap of the 1st test cock. My cap is not metal. It is made of black plastic attached with a rubber band, one end is a small loop as a washer for the cap, the other end is a large loop to loosely connect to the collar. A 7/16”...

I replaced 3 , new from shop, but same issue again and again. I tried 1 inch, zurn (don't remember model number ) as well as watts (800m4qt) PVBs. What is wrong I'm doing here . Why all PVBs are leaking from top ? By the water pressure is not more than 50 PSI.

My condo builder installed American Standard Kitchen sink spray head stopped working today and identified the issue as: A clogged check valve (a blockage of black grit and grease -- not sure what it is from, although we replaced the old water heater last year that was 9yrs old that had liner...

https://imgur.com/a/AeLl5FE Went on vacation for two weeks, had 24" of rain in one/two days, came home to a partially dried out, previously-flooded basement. Not sure where the water came in. Currently removing plywood and drywall and insulation to get rid of mold, and to investigate cause...