"Bob M." wrote in message

For a year or two, probably. Does it have a rubber flap in it or is it a
real check valve? If it's a check valve, don't use it. They rattle after
some time. (i'd question the rubber flap kind too; they'd get stuck in
the 'outflow' direction eventually)

Another point about check valves. Some are swing checks that must be mounted
horizontal. Spring checks can go vertical. Personally, I'd not use one