The little diaphragm
in a siphon break (vented loop) air valve does wear out or become degraded by salt
and sea water
minerals, requiring replacement of the valve. If the valve isn't clogged or crusted, you're not likely to notice the pinhole(s) or miniscule tears in the diaphragm
. The warmer the water
, the higher the salt
and mineral content, so periodic cleaning
will help to extend the life of the rubber diaphragm. But eventually everything wears out and air valves aren't expensive.
Because air valves are typically sold separately from loops, a lot of boat owners don't even know they exist...the only solution they can think of that will put an end to water or waste squirting out the hole in the nipple on the top of the loop is to put a vent line on it.
BAD IDEA because the tube has to be so small--only 1/4" inner diameter--that it very quickly becomes clogged at the connection with salt and sea water minerals, turning the vented loop into an UNvented loop that no longer has any ability to break a siphon. Because the vent line has solved
the pesky squirting problem, it's out of sight, out of mind, so it's never cleaned.