Peggie Hall wrote in news:4jmnf.32927$q%.3104
@newssvr12.news.prodigy.com:

Jeff wrote:
Just curious - do most new boats come without the vented loop,

Toilet mfrs do not include vented loops because they're only needed if
the toilet is below the waterline and/or discharges below the the
waterline...so a good number would be discarded, adding needless cost
to
all units. So it's up to the builder or the owner to install 'em.
Some
builders do, most production builders don't.

or is
this caused by poor refits (or both)?

For production builders, it's about cost. Among owners, many don't even
know what a vented loop is, much less whether they need one...I fielded
a post on a forum recently from someone who'd just replaced his toilet
and reported how he was able to discard about 8' of intake hose because
his new toilet had only a short piece of hose connecting the pump to
the
bowl instead of all that extra hose and a fitting he couldn't figure
out
the need for.

Also, do the vents get clogged or
fail on their own? How often should they be cleaned out?

The vent should have an air valve in it that only allows air INTO the
line to break a siphon (which is why the intake loop has to be between
the pump and the bowl...if it's installed between the thru-hull and the
pump, it interferes with the pump's ability to prime)...and yes, the
air
valves do get clogged up with salt or waste...and yes, they wear
out...requiring periodic cleaning and/or replacement.

But because the air valve in most loops is a replaceable item, often
only sold separately instead of being included with new loops, many
boat
owners don't know air valves exist...and without the valve, the
waste/flush water will squirt out the hole in the top of the loop where
the air valve should go when the toilet is flushed. It never occurs to
most people that there's a part missing...instead, they put a vent line
on it...which is the WRONG thing to do because that line can only be
1/4", and so it quickly becomes clogged by waste squirting into it,
turning the vented loop into an UNvented loop that no longer can
function as a siphon break...it becomes just a high arch in the line.

Although a vented loop can break a siphon--which is always started by
PULLING liquid through a line--it cannot prevent water from being
PUSHED
through a line...which can happen while underway due to the pressure of
water against the hull and any open thru-hull. It's an effect known as
"ram water"--water being rammed up a line. So a vented loop will not
prevent water from flooding and overflowing the bowl while underway,
only while the boat is at rest. So it's advisable to keep all head
seacocks closed except when actually in use while aboard AND when away
from the boat...and any tank overboard discharge thru-hull closed at
ALL
times except when actually dumping the tank...'cuz if water can flood
the toilet, it can also flood the tank. If the head seacocks are in
locations that are so inaccessible as to make keeping 'em closed while
aboard except when using the toilet, install shutoff valves in 'em
right
next to the toilet.

Btw...something the first poster said:

The boat has now been pumped out and is afloat again and on inspection
there is no obvious reason why the boat would take on so much water to
sink the boat in a 12 hour period since it was last viewed...the only
explanation as to the cause that has been offered is that the bow wave
caused the toilet to overflow and created a syphoning effect which in
turn filled the yacht with water.

That possible explanation makes it obvious it was noticed that the head
seacocks were open...how much MORE obvious a reason would anyone
qualified to inspect the boat need???? And if they weren't closed
after
raising the boat, that boat is gonna sink again (if it hasn't already)!


Oh jes can you draw usa a picture?