Looped Vent Line

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Peter Ouzts

Hi, I'm a fairly rookie boat owner who is a part-time liveaboard. I recently had to replace my aluminum holding tank with a new plastic tank. The old vent line was replaced and I didn't really have time to investigate it. So I just looked this weekend and found that the vent line (1 1/2") goes fairly horizontal until it reaches the side of the hull then snakes vertically to the hull penetration. Which I'm assuming is bad. But what's worse is that it appears that the vent line "loops" vertically above the hull port then back down to the hull fitting. I'm guessing this is the mother of all bad vent line installations. Is my hunch true? Should I get rid of the vent loop? Given that I am stuck with a vertical stretch should I install a bigger vent line? Thanks
 
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Peggie Hall/HeadMistress

Take the loop out...

And sometime between seasons, reroute it. A larger vent line in a vertical run won't help.
 
Jan 2, 2005
779
Hunter 35.5 Legend Lake Travis-Austin,TX
Are you saying...

the "vent" line is 1 1/2 inch? That's the size of input and discharge lines!!! Standard "vent" is 5/8 I believe and an increase to 1" max. is a good idea. You do not want any loops in the vent, needs to be as horizontal as possible.
 
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Peggie Hall/Headmistress

No reason why a vent shouldn't be 1.5"

The bigger, the better. The only reason the "standard" vent line is 5/8" is because someone somewhere established 5/8" as the "standard" size for fuel and water tanks...and so applied the same size to holding tanks without any thought whatever to the idea that waste isn't fuel or water...and I can think of at least half a dozen more examples, starting with vertical vent lines. Catalina is the worst...not only are their vent lines vertical, but they terminate inside a rail stanchion that only has a tiny slit in the back of it that's constantly clogged.
 
May 17, 2007
180
HUNTER 25.5 St. Augustine
pls explain why vertical vents are bad

New to this also but I understand physics a bit. So I'm curious...Why is a vertical vent line not as good? Thanks, Steph
 
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Peter Ouzts

Duh!!

Hi Folks, Well, first, duh!! The vent line is 5/8", i.e., standard. Not sure why I have 1-1/2" on my brain ... sorry. I will take the loop out because that is fairly easy (only need to be a semi-contortionalist). Re-routing is not so easy but I will give it a shot. Thanks for your help. Peter Ouzts
 
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Landsend

The vent line could be routed this way...

The vent line could be installed this way to stop water from backing in when your sailing with your rails down.
 
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