# Holding Tank Vent Clogged?



## TSOJOURNER (Dec 16, 1999)

Please bear in mind I'm a new boat owner, please be kind if I seem a bit ignorant. This is my first experience using a marine toilet.

A week ago my holding tank overflowed. I noticed a bad smell in the cockpit one morning. I traced the stench and effluent back to the waste pump out cap. Ever since that mess was cleaned up and the tank pumped out, I have been noticing a foul smell for a few minutes in the cabin immediately after using the head. The smell is more like methane (I think) than specifically human waste. I also here a hissing sound in the v berth after I flush. I didn't notice this before, but can't be certain if this is normal behavior. The smell resides after a few minutes. I can see the lines coming out of the holding tank in the v-berth. They all seem fine, good seals and all.

I suspect the vent line might be clogged somewhere near the exit vent. Does this sound reasonable? If so, what's the best (least disgusting) way to clear the line?

Also, it appear that their is fluid in the vent line. I can see bubbles traveling up the line after a flush, is this normal?

Any ideas\suggestion will be graciously received.

Thanks


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## CalebD (Jan 11, 2008)

Here is what I suggest you do.
Pump out your holding tank. Once the tank is empty use a fresh water hose to force water through the vent line. This should help clean out any remaing crap left in the vent and push it back into the tank. It is quite important that the vent line be free and clear of obstructions solid or liquid. If the vent is plugged you will not be able to suck everything out of the tank when you try to pump out. 
To keep the head (toilet) smelling its freshest you should flush it once or twice using only fresh water.
Next, run some more fresh water into your holding tank from your pump out fitting (a couple gallons would do). Pump all of that out again.
Now would be a good time to put some K-O tank treatment bacteria in the tank.
I hope your vent line did not discharge too much stuff overboard or leak somewhere into your bilge.
Good luck.


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## celenoglu (Dec 13, 2008)

Some plastics transfer the odours through their body. Specially low quality hoses might cause this problem. In this case it is agood idea to change the hoses with good quality hoses. Another alternative is to use aluminum tape to cover all the hoses.


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## sailingdog (Mar 19, 2006)

Check the vent line for insects too... a lot of times wasps and other insects will take up residence in the holding tank vent line. It would help if you said what boat you had, but I'm guessing its a Cape Dory 28 from your username.  

Another common cause of vent line blockage is over filling the holding tank, and the sewage ends up in the line and ends up clogging it. Upgrading the vent line to 1" hose can help reduce odor and clogging problems, so is a worthy upgrade in many cases.


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## CLucas (Feb 10, 2007)

Is the hissing sound coming from the vent line connection on the holding tank, or the other end of the vent line? What about the connection to the thru-deck fitting? If the connection is good from _inside _the boat, I would suggest probing a bit with a small piece of wire from the _exterior _to see if there is any debris or, as has been suggested, an insect nest, etc.


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## TSOJOURNER (Dec 16, 1999)

Thanks for all your suggestions, the problem is resolved.

I pumped out the holding tank, filled it with fresh water, then attacked the vent line. Turns out the vent line had a leak! That explains the hissing sound. The vent line was very long and made some awkward bends, I intend to resolve this with a shorter, more direct routing when I replace the line tomorrow.

Thanks again for your help. I'm amazed how quick you all responded with useful feedback. I'll be back with my next 'challenge' tomorrow


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## sailingdog (Mar 19, 2006)

Gary—

Run the line as straight as possible The better the tank vents, the more likely you'll have good aerobic bacteria in it, rather than the nasty anaerobic (and stink generating) bacteria.


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## ereiss (Nov 25, 2002)

You might want to get Peggy Hall's book on marine sanitation. She is quite rightly known as the Headmistress. She will also answer your questions.

"Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and Other Sources of Aggravation and Odor" 


Hope this helps.

Ed Reiss


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