Holding Tank Vent Line

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Jan 29, 2008
20
Oday 30 Marinette
I'm thinking about refitting a very old holding tank and hoses on my 1984 Oday 30. Everything looks pretty straight forward except that the vent line has a Y connector connected to two short pieces, one leading to the bow end of the tank and one leading to the aft end of the tank. Is that a good connection for venting the holding tank?
 
Dec 2, 1997
8,954
- - LIttle Rock
No, not good

It's apparently a PO's idea of increasing ventilation to the tank without installing a second vent fitting. Running one vent line forward is a good idea, but the wye connector defeats the "cross ventilation" because air forced in the bow thru-hull will take the line of least resistance, which is straight to the aft thru-hull without going through the tank.

If the forward vent line is straight and < 3' long...it's the only one you need.

You say the tank is old... if it's aluminum, now is the time to replace it. If it's plastic, it should be ok.
 
Jan 29, 2008
20
Oday 30 Marinette
Thanks Peggie. The front vent line is less than 3'. The aft vent line is about 4.5' and has a sharp incline. Should I leave the aft vent line where it is and install a bow vent for cross ventilation? If so, I would probably have to change the hose, what type of hose do you recommend. Also my holding tank is plastic so I probably won't change it out. I just want to eliminate the odors.
 
Dec 2, 1997
8,954
- - LIttle Rock
I wouldn't bother with an aft vent line...put a threaded plug--available from any hardware store--in the tank fitting. Ideally, I'd install a new vent thru-hull forward of the tank, but as short as the line to the existing thru-hull is, I'd just go with it for now.

As for hose, use Trident 101 (available from the chandlery on this site) for your 1.5" head discharge hose and pumpout line....Shields or Trident #148 for your head intake line and vent line.

I also suggest you check out the link in my signature...it'll take you to a comprehensive "marine toilets and holding tanks 101" manual that will help you learn how to install and maintain a system and how to prevent and eliminate odors.
 

BobM

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Jun 10, 2004
3,269
S2 9.2A Winthrop, MA
Peggy, regarding odors, the PO of my boat replaced everything, but it still smells badly. I think he used to correct hose (thick white stuff), but did what appears to be a marginal job of cutting it to fit and clamping it. I know that that hose is very difficult to work with. Are tips for working with it covered in your book? I think I may replace it all or at least attempt to reclamp it all, replacing any pieces he cut too short. Also, are those holding tank aerators effective at eliminating odor? If they are, I may bit the bullet and install one. My Wife is complaining about odor and when you open the lockers where the hoses / tank are it will blow you away.
 
Dec 2, 1997
8,954
- - LIttle Rock
Aerator won't solve your problem

Unless a tank is leaking, a holding tank cannot be the source of odors INSIDE a boat...'cuz unless the tank is leaking, odor from inside a tank has only one place to go: out the vent line. So nothing you do the contents of a holding tank will solve an odor problem inside a boat. (I cannot count the number of times I've posted this.)

Most likely sources are permeated hoses, wet dirty bilges, wet dirty sumps, water trapped under the sole. A wet dirty bilge can make a whole boat smell like a swamp and even a sewer...and if your ice box and/or shower drain into the bilge, you can bet real money that your bilges stink. I can't count the number of people who've contacted me after they've replaced their entire sanitation system in an effort to get rid of what they thought was "head" odor, when all they really needed to do was clean their bilges and sumps--really CLEAN 'em and flush ALL the dirty water out instead of just dumping some kind of cleaner into 'em and calling it done.

So clean your bilges and sumps...test your hoses to make sure they have permeated before replacing 'em.

And yes, all of this--and how to replace hoses too--is covered in detail in my book.
 
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