View Full Version : Holding tank

08-08-2001, 09:15 PM
Many boats have problems with odiferous heads. I want to fabricate a custom holding tank of about 30 gallons for a wooden sailboat head. What materials and methods must be used to prevent odors from migrating thru? Anyone have experience with this?

08-08-2001, 09:57 PM
William,I have some experience over in 40 yrs of boating,but never approached this subject real scientificly.I did experiment some,spent alot of money and concluded that odor is going to be a part of boating life.
The question for me becomes,how much odor.
First,review sites like the boating community,yacht survey.com(Pasco)is the pro.surveyor,and his site may have an article on this topic.Besides it is an excellent site.Pasco is very well informed.
Now,my own experience.The odor will migrate thru most hose walls,but the stuff made just for this purpose is really the best.Hose connections are the next biggest problem.
I solved most of this issue by making sure I used a longish piece of the heavy walled white water pipe as my connecting points for the hose.That way I could get lots of hose slid over the pipe,and with a material like boatlife as a sealant between the hose and the pipe,I achieved a pretty gas/odor tight seal.
Containers.I have had all kinds,and the bladder is the worst,while the very thick poly type stuff was the best.If I were going to build one,I would probably build the box of thick material and encapsalate it in glass cloth and resin.This last part is a pure guess.
There is a guy on the forum called chemist who along with his experience may be able to provide some of the chemestry that will explain why certain materials will or will not do the job.

[This message has been edited by dasboat (edited 08-08-2001).]

David Ray
08-08-2001, 10:09 PM
Peggy Hall is the unmitigated Expert on these subjects having done some work with the Gov't etc. on this subject. Smell is NOT necessary acording to her... There is a whole sight devoted to this topic where she goes into the causes of odors etc. I don't have the sight but a mere search on her name on www.google.com (http://www.google.com) will reward you with an onslaught of urls related to her...

For what it's worth (my 1.5 cents)


08-09-2001, 06:11 AM
Pay very close attention to Peggy's site. I obtained 1/4 inch polyethylene from READ Plastices and along with their "welding/soldering material fabricated Ta'ana Maris tank and then heavily glassed it. I also left plenty of ventilation room around the tank, although the under sole bay was isolated from the frames fore and aft of the area. Then I plumbed a wooden air shaft from the deck to the bilge alongside the bulkhead for the head/shower and on the deck there is a Nicro solar vent in constant operation in exhaust mode. On the other side of the boat is a similar air shaft with a solar vent acting as an intake. There is a sealed half pipe of glass epoxy running from the compartment just forward of the tank area to the compartment aft of the tank area for drainage via bilge pump. Ventilation is the key. Make sure you have access through the cabin sole for maintenance to any macerator pumps/through hulls etc.

Scott Rosen
08-09-2001, 08:33 AM
I agree with dasboat in that you should use ONLY the hose designed for the purpose and the thick poly container.

The weak points in the system are the diaphram in the pump and the vent hose. In my holding tank, any odor comes from the pump diaphram, which is a thin, flexible rubber-like material. It is completely ineffective in containing the odors. I suppose I could try to build an air-tight box for it, but that's not practical. Here's what I do. I buy a large amount of the strongest anti-odor holding tank treatment I can find and add a hefty dose with each pumpout. The warmer the weather, the more treatment you will need. This is not a place to pinch pennies. For the vent hose, use the same hose that you use for the rest of the setup, not the cheap, clear stuff.

Nora Lee
08-09-2001, 09:58 AM
On 4th of July weekend, my Captain decided to remove our Raritan head for a rebuild at home, put said head in "George" our 1990 Ford Pick up, forgot to put the tailgate up and shattered the bowl all over the causeway.

The next day I purchase a Sanipotti which can be permanently mounted to a y valve as well as be pumped out, or can be dumped down a marina toilet.

The potti usually lasts about a week as it has a 6 1/2 gal. holding tank. This temporary solution may end up to be our permanent head. No moving parts to worry about, very little odor and serves us well. Our air pollution aboard has been greatly resolved.

A Happy 1st Mate,


08-09-2001, 12:40 PM
Has anyone tried the composting marine toilets (SUNMAR is one manufacturer, no connection or endorsement real or suggested)? It seems to me that carrying around a bag of the compost material and cranking the composting drum over once a day beats smells, pumpouts, pumpout fees, plumbing woes, etc.

They run a grand or so, but that can't be more than a good marine toilet, tank, and peripherals.


08-09-2001, 02:37 PM
ptrrd,Seems to me there was a thread here some time ago(this year) about that idea.
WH,that might be worth looking at.Anyone remember?

Dale Harvey
08-09-2001, 04:30 PM
Paladin's tank is by far the best I have ever heard of. Definately Rolls Royce quality and worth the effort. Polyethelene is the only thing that will work with sewage chemicals and his structural glass overlay eliminates all the pitfalls of straight plastic tanks. The only thing he didn't mention is the need for internal tank baffel plates and removeable cleanout ports. You would be best off with a "V" or rounded bottom and don't run the baffel plates clear down.

Mark Van
08-09-2001, 04:38 PM
I purchased a Sun-Mar composting head last october, and have been using it in a travel trailer, and then had it installed in my boat, which hasn't been launched yet, but the toilet has been in use. (try using a standard marine toilet when your boat isn't in the water)
On the earlier thread, I remember reading Phil Bolger's comment on his, and it wasn't very favorable.
I will agree with a few of his comments. It could have been built better, and the fan was way too loud. I replaced it with a Vetus 12 volt ventilater, and it is much better.
If you install it on a boat, and don't have 110 volt power, you must have a way to drain out excess liquid. I rigged a way to pump it out with a diaphram pump, and it is satisfactory, but a holding tank under the toilet would be better. It doesn't have to be very big, it would probably take two people a couple of weeks to fill a five gallon tank. There is a slight odor coming out of the vent, but I havn't tried the charcoal filter that was supplied yet, so I don't know how well it will solve the problem. It doesn't smell like s**t, more like good muddy compost. However, if the 110 volt heater is used to evaporate excess liquid, the smell is much stronger, like stale piss, which is what it is.
Even though I am not 100% satisfied with it, it still beats any other alternative. It is impossible to clog, easy to install, and requires no through-hull fittings.
The Marine/RV model that I have would probaly not be big enough fore two people full time, but for weekend and vacation use, would be OK.

08-09-2001, 07:22 PM
I've rebuilt several boats and have always installed a welded aluminum holding tank, with double clamps ( a little googe on the connection doesn't hurt) and a good vent pipe, at least as large as the pump-out pipe. Carry it up as high as you can get it and nature will handle the odors. By the way, use fresh water to flush the head and your odors are reduced by more than 60% to start with. Salt water and sewage form hydrogen sulphide, the stuff that stinks!

08-09-2001, 08:01 PM
sorry about an INCOMPLETE note....The tank in Ta'ana Mari is properly baffled, I refer to Peggy Hall's web site, there is a complete description of how it should be done. The tank itself is "v" shaped as the boat is a wineglas configuration similar to Lyle Hess' boats. Additionally there are clean-out ports on top accessible when you lift the cabin sole and the macerator pump is
mated directly to the tank....making for short connections...to a "Y" valve for overboard or deck pump-out fitting. A good
vent to topsides is definitely necessary, and we do use fresh water into the head to reduce the hydrogen sulphide smell. Additionally...periodically I drop in a package of Fleishmans yeast into the head to stir things up in the holding tank.....seems to work well. The head is a Baby Blake and has never failed although every couple of years I tear it down and put in a new overhaul kit...going 8 years now. The entire tank assembly cost about $40 in materials and a week and a halfs work...

08-10-2001, 07:14 PM
Nora, the Captain is guilty of destroying ship's vital equipment? Surely you aren't going to let him get away with that? Seems to me that he ought to suffer at least a (temporary?) reduction in rank to First Mate while the current First Mate should be awarded command of the vessel. I wouldn't call it mutiny exactly . . . . http://media5.hypernet.com/~dick/ubb/wink.gif