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Boat Sank due to Syphoning Effect



 
 
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  #1  
Old December 12th 05, 10:16 AM posted to rec.boats.cruising
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Default Boat Sank due to Syphoning Effect

A friend of mine has a Beneteau 345 moored in Corfu, it was due to be
lifted out for the winter this morning but unfortunately he had a phone
call from the Marina to say his boat had sank! The boat was stern on to
the pontoon and it was only the ropes holding the stern end out of the
water. There are no other boats on the pontoon as they have already
been lifted out.

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 evening before the boat sank a large power craft powered at speed
through the Marina and created a very large bow wave, 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.

Anyone heard of this before?

Ads
  #2  
Old December 12th 05, 03:57 PM posted to rec.boats.cruising
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Default Boat Sank due to Syphoning Effect

phasmatis wrote:

The evening before the boat sank a large power craft powered at speed
through the Marina and created a very large bow wave, 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.
Anyone heard of this before?



Many times...but it's unlikely that the large wake had anything to do
with it. Head seacocks left open when no one is aboard are the leading
causes of boats sinking in their slips.

His toilet is below the waterline...I'd bet real money that a) he's
never installed a vented loop in the head intake...and b) he never
bothers to close the head intake (nor the discharge either) seacock when
he leaves the boat, foolishly relying on the wet/dry valve in the toilet
to prevent water from overflowing the bowl. Either the valve failed
(very common), or the toilet was left in the wet mode. It only takes a
few hours for enough water to flood the boat via the toilet to sink it.


--
Peggie
----------
Peggie Hall
Specializing in marine sanitation since 1987
Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and
Other Sources of Aggravation and Odor"
http://www.seaworthy.com/store/custo...0&cat=6&page=1
http://shop.sailboatowners.com/books...ku=90&cat=1304
  #3  
Old December 12th 05, 04:17 PM posted to rec.boats.cruising
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Default Boat Sank due to Syphoning Effect

Peggie Hall wrote:
....
His toilet is below the waterline...I'd bet real money that a) he's
never installed a vented loop in the head intake...


Just curious - do most new boats come without the vented loop, or is
this caused by poor refits (or both)? Also, do the vents get clogged
or fail on their own? How often should they be cleaned out?

Thanks
  #4  
Old December 12th 05, 07:49 PM posted to rec.boats.cruising
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Default Boat Sank due to Syphoning Effect

On Mon, 12 Dec 2005 14:57:08 GMT, Peggie Hall
wrote:


His toilet is below the waterline...I'd bet real money that a) he's
never installed a vented loop in the head intake...and b) he never
bothers to close the head intake (nor the discharge either) seacock when
he leaves the boat, foolishly relying on the wet/dry valve in the toilet
to prevent water from overflowing the bowl. Either the valve failed


I would second that. Once going below to use the toilet noticed bowl
was almost full of seawater. Toilet pump valve had failed. Lucky us,
top of the bowl was just above waterline.

We usually open the toilet intake seacock when we get to our boat and
have it open as long as we are under way. Have reconsidered that
practice since then.


Mike




  #5  
Old December 12th 05, 08:38 PM posted to rec.boats.cruising
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Default Boat Sank due to Syphoning Effect

On Mon, 12 Dec 2005 20:49:04 +0200, Mike the Spamkiller
wrote:

We usually open the toilet intake seacock when we get to our boat and
have it open as long as we are under way. Have reconsidered that
practice since then.


==========================

You can flood via the output seacock as well if the right valves fail.

Both input and output shoud have vented loops well above the
waterline.

  #6  
Old December 12th 05, 09:11 PM posted to rec.boats.cruising
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Default Boat Sank due to Syphoning Effect

On Mon, 12 Dec 2005 14:38:07 -0500, Wayne.B
wrote:

On Mon, 12 Dec 2005 20:49:04 +0200, Mike the Spamkiller
wrote:

We usually open the toilet intake seacock when we get to our boat and
have it open as long as we are under way. Have reconsidered that
practice since then.


==========================

You can flood via the output seacock as well if the right valves fail.

Both input and output shoud have vented loops well above the
waterline.


and better keep seacocks closed or else taking a leak get more serious
meaning

Mike



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  #7  
Old December 12th 05, 09:24 PM posted to rec.boats.cruising
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Default Vented loops and suction (was) Boat Sank due to Syphoning Effect

Well, this thread has me thinking, as neither of our heads has vented loops
in the intake line, and the aft head is distinctly under the waterline (fwd
isn't except on sharp port tack).

So, if I understand vented loops properly, suction gets air, rather than
water, thus preventing siphoning. So, how do you suck in the supply water
if the supply line is vented???

L8R

Skip, scratching his head, pardon the expression (solidly asking pardon for
the other - inferred solid - expression)

--
Morgan 461 #2
SV Flying Pig KI4MPC
http://tinyurl.com/384p2 The vessel as Tehamana, as we bought her

"Twenty years from now you will be more disappointed by the things you
didn't do than by the ones you did do. So throw off the bowlines. Sail
away from the safe harbor. Catch the trade winds in your sails. Explore.
Dream. Discover." - Mark Twain


  #8  
Old December 12th 05, 09:38 PM posted to rec.boats.cruising
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Default Vented loops and suction (was) Boat Sank due to SyphoningEffect

The vent goes between the toilet pump and the toilet bowl... not
between the inlet and the pump

bob

Skip Gundlach wrote:
Well, this thread has me thinking, as neither of our heads has vented loops
in the intake line, and the aft head is distinctly under the waterline (fwd
isn't except on sharp port tack).

So, if I understand vented loops properly, suction gets air, rather than
water, thus preventing siphoning. So, how do you suck in the supply water
if the supply line is vented???

L8R

Skip, scratching his head, pardon the expression (solidly asking pardon for
the other - inferred solid - expression)

  #9  
Old December 12th 05, 10:53 PM posted to rec.boats.cruising
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Default Boat Sank due to Syphoning Effect

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)!

--
Peggie
----------
Peggie Hall
Specializing in marine sanitation since 1987
Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and
Other Sources of Aggravation and Odor"
http://www.seaworthy.com/store/custo...0&cat=6&page=1
http://shop.sailboatowners.com/books...ku=90&cat=1304
  #10  
Old December 12th 05, 11:05 PM posted to rec.boats.cruising
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Default Vented loops and suction (was) Boat Sank due to SyphoningEffect

Skip Gundlach wrote:

So, if I understand vented loops properly, suction gets air, rather than
water, thus preventing siphoning. So, how do you suck in the supply water
if the supply line is vented???


Skip, have you ever bothered to the read the manual for your toilet? It
includes drawings showing the locations for both discharge and intake
vented loops.

If you don't have a manual for it, download and print one from the mfr's
website. Not only do the manuals illustrate where to put the loops, they
also include exploded diagragms of the pumps and most have
trouble-shooting guides.

That said, there are some very high end manual toilets--W-C Skipper,
Groco EB and Model K--that don't have the short piece of hose connecting
the pump to the bowl...the only place TO put a vented loop in the intake
is in the line between the thru-hull and the pump. However, the design
of these toilets also makes a vented loop in the intake unncessary.

There's no way to put one between the pump and the bowl on most electric
macerating toilets either...it has to go between the thru-hull and the
pump. Instead of just an air valve in the top of the loop, it's
necessary to intall an electric solenoid valve that's wired to the flush
button.

--
Peggie
----------
Peggie Hall
Specializing in marine sanitation since 1987
Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and
Other Sources of Aggravation and Odor"
http://www.seaworthy.com/store/custo...0&cat=6&page=1
http://shop.sailboatowners.com/books...ku=90&cat=1304
 




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