Der,
Suppose you put a nozzle on an air line that hadn't had its separator drained recently. If you directed it towards a nearby wall and opened it slightly, I don't think it would take long to see a deposit build up. I think that is what our garage electrician saw on the wall near the sprinkler head. I was just there fixing the XL3 system when he told me why I had a supervisory on that zone. A contractor did alot of other work before listening to him and replacing the head.
The 2 check valves probably hadn't been checked in years. The pumps are in parallel. I was there because they suspected a leak in the yard as a cause for the jockey short cycling. But when I gated off everything coming off the manifold, we were still losing pressure at the same rate. That's when the check valve became suspect. We gated off at the source to verify. They come in to run tests on both fire pumps but I'm not aware of any specific tests on the check valves or required maintenance on them.
Joe
