Holding tank vent line

[Deepdraft]

Hi -

I read that the holding tank should be run with as few bends and as horizontal as possible. My tank is in the bow. Do folks run the line straight through the hull? Previous owner ran it up to the chain locker.

Thanks.

[Deepdraft]

Meant to write the holding tank vent line should be run...

[Lagoon4us]

Points to consider,
1) In a overflow/tanks full situation emulsified poop may flow through it so terminate it to a point where this wont be a problem, ours goes from top of tank to a skin fitting just above the waterline.
2) Smells/methane will vent through it so the down low spot is also best.
3) If you have an overflow event remember to shove a hose in the outlet and backflush it to ensure it's clean.
Note: Don't allow the tank when backflushing to receive full tap pressure as you may void the tank.
Cheers

[Deepdraft]

Thanks- all good information. If i run it straight from the fitting through the hull, is the s special thru hull fitting made for venting?

[Lagoon4us]

Any type you like and are happy with, mine is plastic and has a small valve in place. A removable clam is good but not necessary, remember and try to visualise your installation when heeling or plowing into a head sea, think about the pumping action going through a wave can do, just think it all out before drilling....

[GordMay]

The holding tank vent fitting should be located above the holding tank and above the
waterline at all angles of heel.
It should also be no less than 24 inches away from any opening into an accommodation space.
Form a gooseneck in the vent line, above the vent fitting to prevent seawater from
back flooding to the tank.
Ensure that the holding tank vent line has a constant rise from the top of the tank to
the vent fitting. Otherwise low spots may fill with sewage and act as a trap,
effectively plugging the vent.
Vent lines should be as short as possible.