I have a 37 Holiday Mansion. I have a holding tank odor problem and wonder if it is the vent on the holdong tank. There is a vent tube that follows the pump out hose to the pump out deck opening but there is not an overboard vent. (like a fuel tank would have). My HM book makes it look like the vent and pump out hose are connected at the deck fitting. When I look down the fitting I can't see the vent attaching anywhere. Also I can't get my body over the stringers to follow the vent tube up the side to see if it is attached or just venting into the bilge.

There is not a vent fitting <like fuel vent> on the outside of the hull.

Questions?? 1> does HM vent the tank to the pump out deck fitting? If so when the cap is closed tight how would the tank vent? 2> Could they have not attached the vent tube or forgot to put in the vent thru hull fitting at the factory?

I am thinking of rerouting the vent tube and installing a fuel type vent fitting.

This has a pretty diagram http://www.southwindssailing.com/articles/0008/KISS0008.html

Bottom line you need a vent. The more air circulated the lower the smell. Without a vent pressure can build and you may get sprayed when you remove the cap to pump out. Peg hall will have a lot more to type

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I am just entering the holding tank zone myself. And my understanding is that you need a vent, the bigger the better. The idea is that the more air that gets to the poop the less it will smell.



Good luck to us all,

There may be several factors attributed to this. Peggy will be able to answer in more detail.

A few culprits off the top of my head:

How old are the heads? What type? The joker valve may be worn out and need replaced. If this is worn, odor will simply migrate back thru the head.

Check your hoses. Hoses break down over time and need replaced. This IS NOT A FUN JOB!!!!! I have done it. But it made a big difference with odor.

Vents can be a tricky subject. Depending on size and location, the odor will escape out the vent, but improperly placed/sized, may offend neighbors, or come back in the cabin.

I highly recommend you buy peg's book. I learned a lot from it.

A bit late seeing this one...not sure how I missed it...



ALL tanks--fuel, water and waste holding--MUST be vented. Fuel and
waste tanks MUST be vented to the outside of the hull. Water tanks
should be...who wants foul bilge odors to "flavor" your water...but not
required.



The tank vent serves two functions: 1. it provides an escape route for
air displaced by incoming water, waste or fuel...without a vent, the
tank would become pressurized, preventing anything from being pumped or
flushed into it...which means you can't fill a water or fuel tank, and
continuing to flush a toilet can cause an eruption or even worse, a
cracked tank. 2. It provides a source of air to replace contents
as they're drawn out. Without a vent, the fuel pump, water pump or
pumpout will pull a vacuum that prevents anything from being drawn out
of the tank once what little air in the tank is exhausted.



So if you can pump out the tank and/or flush the toilet without any
backup--and there's odor each time you flush, the tank has to be vented
somehow. If there's a hole in the cap of the deck pumpout fitting, the
vent very well may be teed into the pumpout line (which is a BAD way to
do it!). You're gonna have figure out to get your body to bend
enough (I'm old enough to appreciate that challenge!) to figure out
exactly what you do have...and then most likely re-route it to a
thru-hull fitting (which you'll also have to install).



Yes...oxygen is the key to odor elimination. When organic matter breaks
down anaerobically (without oxygen), it converts to sulphurous gasses
that stink...but when it breaks down aerobically (oxygenated), it
converts to CO2, which is odorless. So the more ventilation to
the tank, the better. However, depending on the size and location
of the tank, it may not be possible to provide enough oxygen to the
tank via the vent(s) to keep the contents aerobic...in which case,
aerating the tank contents may be the best answer.



However, the tank is rarely the source of odor INSIDE the
boat...because unless it's leaking, odor from inside the tank has only
one place to go: out the tank vent. So if you're trying to find
the source of odor inside your boat, the first place to look is the
hoses...sanitation hoses can become permeated with odor.
Replacement is the only cure. If the boat is in salt water, stagnant
sea water trapped in the head intake is another source of odor...but
usually goes away once the stagnant water is flushed out when you come
aboard again.



"Vents can be a tricky subject. Depending on size and location, the
odor will escape out the vent, but improperly placed/sized, may offend
neighbors, or come back in the cabin."



Only if tank contents stink...and assuming that tank contents HAVE to
stink is a false premise...they don't have to...in fact, can be made
completely odorless. Unfortunately, few boat builders bother to
give any thought to actually designing a sanitation SYSTEM...they just
drop components--toilet, tank, treatment device--into any empty space
and run hoses wherever they have to to connect it all up.
Or they start from that false premise, and in their efforts to keep
odors away from people, do things that actually create MORE
odor. But builders aren't the only ones...the K.I.S.S design in
woodboat's _link_ is a great e example of how NOT to install a holding
tank!






peghall38564.5422222222

so I was able to climb up and see that my vent tube is infact attached to the overboard vent fitting. Should I have a vented loop?

A vented loop is a siphon break... only required in lines connected to
below-waterline thru-hulls--to break a siphon. There's no reason
whatever for a vented loop in a vent line...vent thru-hulls are well
above waterline and nothing but air SHOULD pass through it.

Peggie,

Why is the KISS method in woodboats reply not a good solution?

Ray