Decomisioning Holding tank question

[Alan Wheeler]

Ohhh if you only new what you swam in Steve ;-) :-)
Yeah I got your point Lodesman and it was a good point. But no, the tank is so huge, I never ever let it get full. Infact, we keep it as empty as we can to eliminate as much possible sloshing around as we can.
I even went to the extent of placing a computer fan inside the large vent hose. I made up a box the fan was mounted in and the thing was placed in line drawing air out of the tank. I thought this may produce a low pressure in the tank. Sadly the fan didn't like a charge voltage above 12V and it rapidly died. So I don't know if it would have worked.
Chrisc, yes electrasan have a unit that has two electrode plates in the tank. I am not sure what they are made from but replacement plates are in the NZ$400-600 price range, so not cheap. It's a great idea and this is what I have considered putting in in place of the main tank. They have two tanks as I understand it and two maserator pumps that control the levels in each tank, with the final tank supposedly pumping "safe" discharge out.
Raritan Engineering | Waste Treatment | LectraSan

[Chrisc]

O.K., I know about this Lectrasan thing - too pricey for me! What I was getting excited about was the notion that perhaps I could put a couple of terminals in my Holding tank and zap it with a few amps and eliminate the smell. I thought that possibly it was something along the lines of lighting a match in the toilet room after you've had a poo. Works a treat to dispel odours.
Isn't it incredible the amount of trouble and expense we go to to move a load of poop from inside to outside - probably not more than 30cm in distance. Whatever happened to 'in the bucket and chuck it?'

[GordMay]

Watts From Wastewater:
New Device Produces Power While Treating Sewage
Science Daily — “A new technology is being developed that can turn raw sewage into raw power. The device, called a microbial fuel cell, not only treats wastewater, but also provides a clean energy source with the potential for enormous financial savings, according to scientists at Pennsylvania State University ...”

Goto: ScienceDaily: Watts From Wastewater: New Device Produces Power While Treating Sewage

More: Fuel Cell Works Supplemental News Page


Marine sewage disposal device - United States Patent 3951803
A marine sewage disposal device connectable to a toilet and flushed by water, in which the sewage is macerated to small particle size, subjected to heat and electric current to destroy coliform bacteria, and subsequently filtered to separate liquids from solids prior to being discharged. Power requirements are relatively low, in the order of 2 to 5 amperes at 110 volts A.C., or less, thereby permitting the device to be used on relatively small craft having minimal generating equipment, such as a standard generator arranged to bypass the usual voltage regulator.
Goto: Marine sewage disposal device - Patent 3951803

[hellosailor]

"2 to 5 amperes at 110 volts A.C., or less, thereby permitting the device to be used on relatively small craft having minimal generating equipment, such as a standard generator arranged to bypass the usual voltage regulator."
Well, the USPO has the job of handing out patents to the widest audience, even if he inventions don't or can't work. The patent isn't a validation of the concept.
First, the gizmo needs the usual voltage regulator bypassed...Sure, they're going to pull high voltage out of the alternator. Rewire alternator, void warranties, run high voltage lines with unregulated voltage in them.<G> Then there's the power draw, 5A@110AC means 550W which still means pulling one horsepower from the alternator, or 45 AMPS of 12VDC load.
Dunno what miracle this patent is for, but I doubt it will take over the "small craft" market.<G>

[Alan Wheeler]

So what power is it producing???

[ssullivan]

Oooh. Just had another possibility for you Wheels. (Just what you needed, right??)

You say grey and black water are going to this tank currently? You say the smell happens in the galley underway when the boat is lively and the sh*t is sloshing around that tank?

Maybe you have some sewer gasses escaping through the galley sink drain! Is there anything to prevent that from happening the way the plumbing is currently set up?

I'd definitely keep the black and grey waters apart specifically for this purpose. Can you cap off the galley drain/plumbing (completely so no gas can pass) next time you take her out for a spin? Can you also cap off all grey water drains everywhere to be doubly sure? Maybe... just maybe... the vent loops you have on the tank are only part of the story. A direct line from sink to blackwater would make for a NASTY sewer gas backup on occasions.

[mudnut]

Wheels,seeing that you have tried everthing under the sun to fix this problem without resolve maybe my thoughts wont sound so silly.#1 Have you ever gone out sailing with the tank completely empty,and,has it produced the same senerio.#2Would the sloshing around while sailing cause the gas to pressurise within the tank,if so,would that cause a difference in your venting system or your sink drains?Now with that last thought,could the PO have installed some sort of hole with a cover plate over it,somewhere,under your galley that you don't know about.If so,then it might just be a case of said cover plate has a deteriated gasket or seal which leaks gas while under sail?I have had other silly thoughts but they stay with me till I die.Mudnut.

[Alan Wheeler]

No thought is silly Mudnut. I would even try standing on my head if you said it would help.
To answer both you and Sean. Yes I have emtied the tanks as far as they can. The macerator pump is on one side of the tank and close to the bottom, but I doubt it will ever get all. I have even pumped out when the boat heels that way to get as much as I can. But with a tank floor of something like 6ft x 3ft alone, the dregs in the bottom must add up to a lot of liquid not being able to be removed.
Sean I have also thought of the sink drains. They drop verticle straight into the tank. But I have S bends with water in them to stop gas from coming up. I have even put the plugs in the sinks incase the gas bubled up through the water. Lastly, I "Y' the 32mm hose into the bas of the sink drain so as the least amount of pressure build up could be found there. But nup.
Mudnut, your suspicion is also mine. The tank is divided in two by a large baffle. I only know it exists as I have seen the same in the fresh water tank. A lot more pleasant a place to go putting your head into :-) Anyways, I also know it exist, because originaly the one side of the tank never filled up compleatly as it had no vent. Thus the air pressure inside would stop the tank filling . When I found that out a put a vent hose on that side of the tank, I thought my problems would be solved. Once again, No. So I believe the issue has to be in the metal tank top plate that is built under the galley. The only thing I have tried that side is to pour in sealants and epoxy and what not to try and seal off the lid. But either it's not the problem or I am missing the hole.
Please, I don't care if anyone goes over what I have already done, so keep it coming. I am desperate and I may have missed something that you come up with.

[FrankZ]

While is sounds like you have tried a lot of stuff, it might be benifical to find a (very good) friend that is a boatie as well. Have this person poke around and look and don't hint, prompt, discuss, or otherwise guide. Let em start with a description of the problem. Sometimes a new set of unbiased eyes (or a nose in this one) will see something you keep staring at and not seeing.

Of course for this job you better be ready to provide a really nice dinner afterwards.

[mudnut]

I think defining the problem comes first.A presure test will tell you that in fact there is a leak.If you cannot reach it you carn't fix it!!Here comes that new kitchen Mr's Wheeler been dreaming of.<Gr>Mudnut.

[Alan Wheeler]

Ummmm, new kitchen, absolutely NOT!!!!!

[hellosailor]

Alan, I think Mudnut's right on this one, a pressure test will confirm if there is or isn't a leak. Either way...sewage smells usually indicate there is inadequate ventilation in the tank, per Paggy Hall's many writings on the subject over many years. If it builds up that kind of smell, it might not be ventilated well enough regardless of whether it is leaking or not.

[Alan Wheeler]

How big an air intake do I need then;-) I mean I have a 32mm and a 19mm hose and set in such away that one draws through the air in one and out the other. So I can't get anymore air in there unless I fitted a bilge blower. I have heard of that comment Peggy Hall made and after I had this issue, I thought yeah well it didn't work.

[seafox]

you could try eating roses for a few weeks!

I have tried all sorts of things to get rid of poo loo smells. I reckon it is worse when the boat is at the marina and not used for a few weeks. A Y valve at the salt water intake where fresh water can be pumped through the system works wonders for a pump loo.

Otherwise, block the holding tank and poo 500 metres from the shore and in over 5m depth where the poo police will leave you alone. You could then fill the tank with some Tui beer. It will kill anything.

[Alan Wheeler]

Good thought, but if there is a leak, the beer will go flat ;-)