Gould 0738 wrote:
If you've got a stinky holding tank, it's a sign of a failing or badly designed
system.

No, it's not...it's only a sign that the environment inside the tank is
anaerobic ("septic"). Nor is the holding tank likely to be the source of
odor inside the boat 'cuz the only place odor from inside the tank has
to go is out the tank vent. Odor inside the boat originates inside the
boat...stagnant sea water trapped in the head intake...permeated
sanitation hoses...a dirty sump...a wet bilge...trapped water below the
sole that can't drain...all of the above can smell like a sewer. I
can't count the number of people who've torn out and replaced their
whole sanitation system trying to get rid of what they thought was
"head" odor, when all they really needed to do was clean--really CLEAN,
and flush all the dirty water out--their bilges and sumps.

Peggie will most assuredly check in with
some corrections, adjustments, or differences of opinion with the following
item. It appeared last month in a regional boating magazine, and may suggest a
braoder scope to solving your problem than
simply dumping perfume down the head.

The article is mostly on the mark...however, there are a few things I
take exception to:

Some of the chemicals in the head treatments we routinely flush are nastier
than the sewage they claim to de-odorize. Bronopol and Dowicil are bacterial
pesticides, and in sufficient quantities can inhibit the effectiveness of
shoreside sewage treatment plants. Formaldehyde is considered a probable
carcinogen. Glutaraldehyde is (literally) embalming fluid. One teaspoon of
Paraformaldehyde can kill a 150-pound adult, while it takes several ounces of
Para-dichlorobenzene to snuff out a human life.

AMEN!! But he forgot to include quaternary ammonium compounds, which are
equally nasty.

The good news is our boats don't have to stink and we don't have to spend $100
a gallon for poisons and perfumes that fail to cure the problem. A properly
installed and maintained marine sanitation system will operate virtually odor
free.

TOTALLY odorfree.

Odors can emanate from any portion of the marine sanitation system, and finding
the exact source, or sources, of a stinky problem can be frustrating. One
workable technique for isolating the source of a smell involves wiping any
suspected area with a clean, slightly damp rag. If odors are escaping from the
area, the rag won't pass the "sniff test" once removed.

That works to check hoses for odor permeation, but wiping down a hard
surface is a waste of time because hard surfaces only collect odors from
other sources, they cannot be the source of any odor.

The head:

Many heads have
sections of pipe that are joined together with gaskets and screws. These joints
will hold forever in a marine supply store or a mail order catalog, but may
tend to work loose in a seaway.

I've not found that to be true in any decent quality toilet...however,
rubber gaskets do wear out eventually, so it could be true if the toilet
is old and badly neglected. I think I smell a sales pitch coming...and
here it is:

If the existing head has seen better days, it might be wise to at least
consider upgrading to one of the VacuFlush (tm) heads. The VacuFlush system
uses a very tiny amount of fresh water for each flush, rather than seawater.
Sal****er sanitation systems are more likely to develop odor problems than
systems using fresh water, as the sal****er itself naturally contains a large
amount of organisms that will breed, die, and odoriferously decompose in the
head, the sewage lines, and the holding tank.

Seawater can stagnate and stink in the head intake, but it makes no
difference in a holding tank whether the toilet flushes with sea water
or fresh. Nor is the VacuFlush the only toilet that uses pressurized
fresh water. It's just the most expensive. Every major toilet mfr offers
at least one pressurized flush water version, some for as little as 1/4
of the price of a VacuFlush.

The sewage hose:

It makes sense to evaluate both condition and system design when examining the
sewage hose. Sewage hose is not immortal, and needs to be replaced after
several years.

Not necessarily. Only hoses that stink need to be replaced...and there's
no predicting how long that can take. I've seen hoses that are more than
10 years old that don't stink...I've seen hoses permeate with odor in
just a few months.


The holding tank:

One of the most critical components of a marine sanitation system is the
holding tank vent.

That much is true...but--

Billions of little microbes are busily digesting the
contents of a healthy holding tank, and some rather wretched smelling gases
inevitably result.

It is NOT inevitable...only if the environment inside the tank is
anaerobic (and I smell another sales pitch coming).

If these gases are allowed to escape to the atmosphere
outside the boat, they will.

They have to escape, or the tank pressurizes. But they do NOT have to
stink!

Otherwise, they tend to escape into the on board
atmosphere and contribute to an odor problem.

Unless there's a leak in the system, there's no way they can escape
inside the boat. And I disagree with almost all of the following...it
assumes that foul gasses are inevitable.

The vent line should exit the top of the tank, should be of generous diameter,
and should lead overboard at a spot where the escaping fumes are unlikely to
reenter the vessel through a portlight or other opening.

He's half right...the vent fitting should be on the top of the tank, and
should be positioned closest to the centerline of the boat to prevent
tank contents from overflowing out the vent while heeled. Ideally, the
diameter should be 1" and the line should be as short and straight as
possible without regard for portlights etc...'cuz if the tank
environment is aerobic there won't be any "fumes" to worry about
reentering the boat.

I knew a sales pitch was coming:

An in-line charcoal filter can be fit
to a vent hose to eliminate some of the odors in cases where no suitable exit
point is available, (but to the degree that the filter will block some of the
air flow through the vent line there is a definite compromise in play).

Noooooooo!!! The LAST thing you want in a tank vent line is a filter. It
creates the very problem it's sold to cure! Not only that, but they cost
a whopping $50 and only last season, and are toast immediately if they
ever get wet.

All in all, though, he didn't do too badly....just contradicted himself
a few times in describing what causes odor and how to prevent it in an
attempt to provide some useful info AND sell SeaLand products.

--
Peggie
----------
Peggie Hall
Specializing in marine sanitation since 1987
Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and
Other Sources of Aggravation and Odor"
http://www.seaworthy.com/html/get_rid_of_boat_odors.htm