[C38] Vented loop for head discharge

[S Orton]

Don,  Your email indicates you have a "vented loop" for your engine sea water cooling?  To me that doesn't sound like a good practice, as you could loose your cooling to your engine with a vacuum breaker on the suction side of a pump.  The scenario- marine growth partially plugs the intake, negative pressure increases on the pump suction, the vacuum breaker opens, and lets air into the pump suction loosing sea water flow.  I would definitely check into this.
Cheers, Steve O  
 



Date: Tue, 1 Nov 2011 08:44:23 -0600
From: maxsoto at gmail.com
To: listserve at catalina38.org
Subject: Re: [C38] Vented loop for head discharge

Steve,  Since the loop+vent breaks the siphon, the "pressure" on the joker valve is from the grey water located between the head and the loop.
Don, same thing happened to the PO, so he made a box that raises the head about 7 inches, and added a vented loop to the intake hose.  Apparently he found he boat with 1' of water. I think that the vented loop for the intake  is enough, so I'm going to remove the riser box. Short people have their feet on the air while seating in the head! 


Regards,


Max


2011/11/1 Don Strong <drstrong at ucdavis.edu>


Steve: I did the vented loop head-to sea retrofit because my insurer demanded it.  Big job! The exit hose goes up the along the hull, through the sink top and reaches an apex are just under the deck. The vent is at the apex. The loop+vent breaks the siphon. I don't see how the grey water problem is any different between "overboard" and "waste tank." When the valve is thrown to tank, grey water sits behind the joker valve just as it does when the valve is thrown to overboard. 

I also installed a vented loop for the sea water intake for the head after we awoke with 6" of water in the boat (someone "moi?" was too sleepy to flip the switch to "dry bowl during the night).  There is also a vented loop on the sea water intake for engine cooling. I recently replaced the vent.
Don


On 10/31/11 11:43 PM, Steve Smolinske wrote: 


Question for anyone with a vented loop in their head discharge.   Looking at it on paper it seems that the pressure of the grey water in the section from the head to the vented loop would be enough to leak back into the toilet bowl.  I know there is a duckbill valve and a flapper valve in the head to stop the reverse flow, but as we all know if you leave the discharge seacock open the head will fill up.   Does the vented loop work because the head pressure of the grey water in the run from head to loop is not as great as that coming from the seacock?  Any experiences are greatly appreciated.   Thanks
 
Steve

 
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-- 
Donald R. Strong
Professor
Dept. of Evolution and Ecology
University of California, Davis 95616
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-- 
Max Soto
C38 #198 ESTANCIA
Puntarenas, Costa Rica

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