Holding tank vent smell and aeration

[Sleeping Bear]

I clean my tank with massive dose of bleach (4 gal bleach in 30 gal tank), but my tank is plastic metal tanks may not like this.

I fill tank 3/4, add bleach, fill tank to top, let sit and pump out.

The reason I do this is I have a light behind the tank to see where the level is, and it doesn't work well if the sides are covered with poop.

But I digress, and go back to my other post about carbon filters. I really don't care what the inside of the tank smells like, it is the outside that counts.

 

[boomerang]

I clean my tank with massive dose of bleach (4 gal bleach in 30 gal tank), but my tank is plastic metal tanks may not like this.

I fill tank 3/4, add bleach, fill tank to top, let sit and pump out.

The reason I do this is I have a light behind the tank to see where the level is, and it doesn't work well if the sides are covered with poop.

But I digress, and go back to my other post about carbon filters. I really don't care what the inside of the tank smells like, it is the outside that counts.

I think I just heard Peggy scream.

 

[AlanT]

I use a carbon filter on the vent tube. It is a granulated carbon water filter with the standard water filter housing upside down and tilted so if there is ever a disaster it can drain back. The filter costs about ten bucks and lasts about two months constant use.

It has to be a granulated filter because the carbon block filters cause some back pressure, ask me how I know!!

I also added a carbon filter on the vent on a prior boat which had a seawater flush. It completely solved the problem. I built it from Schedule 40 pipe and used carbon granules from a pet shop (it is used in fish tanks).
~A

 

[NightCrawler]

Did you PM Peggie? She might have something else to try.

Peggy knows her stuff. Been on the phone with her a couple of times. We struggled for a long time and ended up with the NoFlex solution. You have to keep on top of it, but odors never returned. Excellent product.

 

[HeadMistress]

I think I just heard Peggy scream.

<LOL> It was a groan actually.

Waste is full of body fats, which creates the scum on the tank walls. Bleach won't dissolve oil or fats, it just removes the color. But detergent will, so next time try a massive dose of Dawn Ultra and let that soak awhile. Better yet, figure out a way to agitate it a bit.

As for vent filters...they actually help to promote the problem they're sold to cure. And like most things, prevention is easier and usually cheaper than cure...and OXYGEN will prevent odors from occurring in holding tanks because odor can only be created in an ANAEROBIC environment. Creating an AEROBIC environment in the tank prevents odor from being generated. A larger diameter, shorter, straighter vent lines is often the solution because it allows better air exchange with the gasses in the tank, but if that's not possible, aeration is the answer. There are many people who've successfully created DIY aerators that work with a fish tank aerator and some perforated hose.

--Peggie

 

[CaptTom]

I'm confused about NoFlex, OxyClean and Sodium Percarbonate.

First off, is SP really one of main ingredients in NoFlex?

From what I've read, SP breaks down into, among other things, Hydrogen Peroxide when it's dissolved in water.

I always thought of OxyClean and Hydrogen Peroxide as bleaching agents. I also connect bleaching with killing bacteria - both aerobic and anaerobic. And it's bad to kill all the bacteria in a holding tank, right? But then how does NoFlex work?

Obviously I'm missing some key facts here.

 

[rslifkin]

In a high enough concentration I'd expect SP to kill bacteria of all types. But in smaller quantities I don't think it's enough to kill aerobic bacteria, but the SP breaking down does release oxygen.

 

[Bacchus]

SPC is a non-clorine bleach. It forms hydrogen peroxide in water which breaks down and produces oxygen which is the key to promoting an aerobic environment and aerobic breakdown of waste that avoids the stink of anaerobic breakdown.
Yes... SPC is listed as the major ingredient (I forget the range but something like 85-95%) note that the mfg does not call it SPC but it's another chemical description that means the same thing.

 

[catalinajack]

SPC is a non-clorine bleach. It forms hydrogen peroxide in water which breaks down and produces oxygen which is the key to promoting an aerobic environment and aerobic breakdown of waste that avoids the stink of anaerobic breakdown.
Yes... SPC is listed as the major ingredient (I forget the range but something like 85-95%) note that the mfg does not call it SPC but it's another chemical description that means the same thing.

And SPC is a whole lot cheaper, and it works a charm.

 

[Brisyboy]

Well, for that pesky smelly tank, I know NoFlex is the go to solution - I used it after discussions (forum and phone) with Peggy and there was no question is solved the problem virtually instantly.

My problem was I kept forgetting to add dose - back came the stinkies. So............plan B I already had one vent line running straight and slightly up hill from the tank. It was about 30mm inside dia so should have helped. Plan B involved running a second vent, same size, from the other side of the tank (also from the top) along side the existing. HOWEVER, on the outside of the hull I installed a small scoop (forgot the name but they are available from chandleries) - horizontally over one of the vent outlets, facing aft. The idea being that the breeze flowing over this creates a venturi effect and sucks air out of the tank, to be replaced by clean (oxygenated) air. I agree the suction must be only very small BUT it has done the job and no smell. BTW, my outlets are side by side so I used the aft one for the venturi. If they were stacked - either one PLUS one either side of the hull would have been just as good, but I had no access.

Thats how I keep plenty of oxygen in the tank.

 

[Comodave]

My tank had the usual 5/8” vent with the filter in it. So that means no air flow through that vent at all. The filter was put in at the factory in a totally inaccessible location. I can see it but no way to even touch it much less change it. So the filter was put in in 1998. Never been changed because you can’t get to it. I added 2 1.5” vents, one to each side of the boat. So there is pretty good air flow through the tank no matter which way the wind is blowing.

 

[Brisyboy]

My tank had the usual 5/8” vent with the filter in it. So that means no air flow through that vent at all. The filter was put in at the factory in a totally inaccessible location. I can see it but no way to even touch it much less change it. So the filter was put in in 1998. Never been changed because you can’t get to it. I added 2 1.5” vents, one to each side of the boat. So there is pretty good air flow through the tank no matter which way the wind is blowing.

Yup, either side is a good solution AND it saves the cost of a scoop

 

[Andy G]

I am about to install a new 160 litre 'plastic' holding tank behing the generator in the ER. I am keen to get it done properly, especially after reading the various posts concerning venting etc.

It seems to me that carbon filters may not be the way to go, but getting adequate amounts of fresh air into the tank is a major plus. I like the idea that George from Brisboy & Comodave have come up with, that is two breather pipes from the top of the tank.

As I am starting completly from scratch I am open to any advice or tips from those who gone gone before.

Cheers & Happy Christmas to all.

Andy

 

[AlanT]

I am about to install a new 160 litre 'plastic' holding tank behing the generator in the ER. I am keen to get it done properly, especially after reading the various posts concerning venting etc.

It seems to me that carbon filters may not be the way to go, but getting adequate amounts of fresh air into the tank is a major plus. I like the idea that George from Brisboy & Comodave have come up with, that is two breather pipes from the top of the tank.

As I am starting completly from scratch I am open to any advice or tips from those who gone gone before.

Cheers & Happy Christmas to all.

Andy

My last boat had a perennially smelly holding tank. Marina neighbors cringed when we flushed. I changed both heads to Marine Elegance and changed supply from saltwater to fresh, changed all hoses and installed a home made carbon filter. Never had another smell to worry about. Never needed any chemicals or additives.

 

[Rated Aargh]

previous owner of my boat installed a simple little aquarium airpump into the top of the tank. he said if the tank starts to smell any just plug that little bugger in for an hour or two and then unplug it (120v). Sure as Sh*t it must apply just enough positive pressure to vent out the tank and the odor goes away.
Just a low budget correction, may not be a final fix type solution but i guess neither is anything else that you have to continually add after each pump out..

 

[Comodave]

previous owner of my boat installed a simple little aquarium airpump into the top of the tank. he said if the tank starts to smell any just plug that little bugger in for an hour or two and then unplug it (120v). Sure as Sh*t it must apply just enough positive pressure to vent out the tank and the odor goes away.
Just a low budget correction, may not be a final fix type solution but i guess neither is anything else that you have to continually add after each pump out..

Same principle as the Groco SweetTank. But it is 12 volts and recommended to run it 24x7. If the poop has enough oxygen it won’t stink. When there is a shortage of oxygen then you get the stinky bacteria.