[C38] Vented loop for head discharge

[Don Strong]

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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