[Public-List] Holding tank vent

[Glennb]

Good call George,  I havent installed the tank or lines yet so, dont really have any experience with how it will work yet.  Makes sense that it wont drain when heeled. Much ado about nothing maybe...!

Glenn

Sent from my iPad

On Mar 4, 2013, at 9:51 PM, George Dinwiddie <gdinwiddie at alberg30.org> wrote:

> Glenn,
> 
> On 3/4/13 11:06 PM, brooks.glenn at comcast.net wrote:
>> John, Great question...
>> 
>> 
>> I dont think one vent line can back fill. the ambient air pressure in
>> a closed tank system will prevent sea water intrusion through the
>> vent line. Certainly did (prevent backfill) in my fishing boat in
>> Alaska, which had a fuel tank vent at the bow.
>> 
>> 
>> But with two 3/4" vent lines, the back pressure in the tank is
>> neutralized and it seems like water could then enter, particularly
>> when bashing to windward. One of the vent lines would be in a gravity
>> feed position above the tank, so conceivably could the tank be in a
>> position then to syphon water back into the boat through the commode?
>> A n asty result to say the least...
> 
> It's the low side that will go in the water. It won't flow by gravity, and I don't see how it will get a siphon going.
> 
> - George
> 
> -- 
> ----------------------------------------------------------------------
>  When I remember bygone days                         George Dinwiddie
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