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Old 24-10-2015, 14:34   #1
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Aeration pumps for holding tanks

Has anyone got any recommendations for good air pumps that run off 12v, use little power, make little noise, and run for years in a boat environment!

sounds like a tall order to me. I know there is the SweetTank, but I was hoping for something a little cheaper.

I've been thinking about bellows with a heavy pendulum that react to boat movement!! so before I get carried away, let me know if there is a pump, many thanks.

PS I don't really want a debate on using an air pump with a holding tank, thats for another day, cheers
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Old 24-10-2015, 15:16   #2
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Re: Aeration pumps for holding tanks

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Originally Posted by mtompson View Post
Has anyone got any recommendations for good air pumps that run off 12v, use little power, make little noise, and run for years in a boat environment! sounds like a tall order to me. I know there is the SweetTank, but I was hoping for something a little cheaper. I've been thinking about bellows with a heavy pendulum that react to boat movement!! so before I get carried away, let me know if there is a pump, many thanks.
PS I don't really want a debate on using an air pump with a holding tank, thats for another day, cheers
There's a little bit more to aerating a waste tank than just a pump and length of hose. If there weren't, Groco's Sweetank system wouldn't have been on the market since 2002 without a single competing product ever hitting the market. So I suggest you read their installation, operation and maintenance instructions to get an idea of what's needed--especially the piping inside the tank--to make your system work. You can find those here: Groco Sweetank installation instructions

Now about your pump...it doesn't have to be a big one, but it does have be powerful enough to aerate contents, not just force noxious fumes out the vent--which may be what leads to debates about aeration. When done right, it DOES work! I'm not aware of any air pumps that run on 12v, but you might be able to replace the motor in a 115v fish tank pump with a 12v motor. However, I'm having a little trouble grasping how a "bellows with a heavy pendulum" would work...I can't even visualize what you mean.

Good luck with it... If can be of help in designing it, let me know.
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Old 24-10-2015, 16:19   #3
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Re: Aeration pumps for holding tanks

Thanks Peggie, I'm definitely going to give it a go, it makes a great deal of sense. I think most basic aquarium pumps use solenoids, it's the AC that gets them going back & forth. I have seen some pumps that use Pistons, therefore a motor.
As for my bellows idea, I'll do a pic
Imagine old style fireplace bellows, pointing up, fix one handle to boat, fix a weight to the other 'free' handle, probably on a longer extension? As the boat rocks the bellows pump air! It's a concept not a design, I bet people could think of loads of better ways to convert the motion of the boat to pump some air? No good in a still sheltered mooring, but who knows!
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Old 24-10-2015, 18:51   #4
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Re: Aeration pumps for holding tanks

I just recently purchased the Marine Metal Power Bubbles from Amazon for this purpose. It's a 12 volt air pump with aerator stones. It cost all of $34 plus tax. It's fairly low power draw (. 3 amps) and reasonably quiet. Most importantly it really does the job of virtually eliminating the bad smell of sewage. I also add a treatment of Raritan's KO after each pump out. The difference the aeration makes is amazing.

The one thing I recommend is also getting a cheap air regulator (cost a couple bucks) to put in line in the hose to decrease the amount of air. Without this regulator the pump is a bit noisier, uses a bit more power (. 5 amps) and simply produces more air than is needed for the job.

I've only had this running for a month, so I can't yet report it's longevity. I can say that I did not see any bad reviews for this product relating to breakdowns. It certainly is a heck of a lot better price than the Graco.

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Old 24-10-2015, 19:17   #5
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Re: Aeration pumps for holding tanks

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Originally Posted by peghall View Post
There's a little bit more to aerating a waste tank than just a pump and length of hose. If there weren't, Groco's Sweetank system wouldn't have been on the market since 2002 without a single competing product ever hitting the market. So I suggest you read their installation, operation and maintenance instructions to get an idea of what's needed--especially the piping inside the tank--to make your system work. You can find those here: Groco Sweetank installation instructions
Something about this smells fishy to me. It is recommended that vent lines be large diameter so that oxygen has access to the tank. It is even recommended that two vent lines be installed so the tank has air cross flow. All either of these recommendations accomplish is to at best exchange the air contents above the tank contents, and at worse just continually force the noxious fumes out the vent so that they never reach high concentrations.

If the above is done, then tank odors should disappear because the contents will be aerobic and not smell - this is the advice always given, correct?

If all that was done was to fit an aquarium pump to continually pump air into a tank's headspace, then this would accomplish all that large dual cross vents could accomplish.

Now we are to believe that there is special magic about Groco's product that can't be matched? I have examined this product closely and find it is simply an aquarium pump connected to an aerator tube (I have lots of experience with aquariums and these are the exact components used in them). There is no magic or technical complexity to it at all. It is simply way over-priced, and I doubt they sell very many of them.

I would like to understand why a large vent line will work wonders, but a cheap air pump (or bellows controlled by a pendulum) continually pumping air into and through a headspace will not work and a special magic high price gizmo is necessary.

Mark
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Old 24-10-2015, 20:07   #6
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Re: Aeration pumps for holding tanks

In 99% of tanks, increased ventilation/oxygen is the solution. But when the tank is in a location that doesn't allow the vent line(s) to provide sufficient exchange of air with the CO2 on the surface, or the tank is too deep for passive ventilation above the surface to keep the contents aerobic, aerating the contents can be solution.

There's no "magic" to the Groco Sweetank...just the knowledge to know that a single column air won't aerate a tankful, it'll only push noxious gasses out the vent...that aeration requires installing perforated piping across the bottom of the tank to provide a "curtain" of air. It took 'em 3 tries to come up with piping that didn't become clogged with sludge. That a pump has to provide enough air to fully aerate...that a too-small pump will only push noxious gasses out the vent, one that's too large will only drive people crazy with the sound of "boiling" water coming from the tank. That the system has to run 24/7/365 (except during extended layup) because when aeration ceases, odor recurs.

But hey...if you think a cheap pump and a length of hose will work, have at it. Occasionally, in tanks that prob'ly didn't need it, that works.
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Old 24-10-2015, 20:22   #7
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Re: Aeration pumps for holding tanks

I hadn't heard of it before. Went to Amazon to check it out. They're marketing it for bait wells and live wells...They say it's for tanks up to 35 gallons, but no mention of the depth...no mention of waste tanks. And they say it's "most effective when used with water renewal systems," which doesn't seem to describe waste tanks. Neither do "stainless steel clips." But I'm fascinated by it and want to talk with 'em, 'cuz it's the first system I've heard about that COULD be competition for the Sweetank.
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Old 24-10-2015, 23:25   #8
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Re: Aeration pumps for holding tanks

Peggy,

It was everything I have read from you that led me to this product. All of your writings convinced me that the way to get rid of my holding tank odors was to make sure that fresh air was being circulated through the tank. While I did install a large diameter air vent hose (1"), there was no easy way to install two of them with one on each side of the boat. The run also had to drop down a fair distance and involved a 90 degree elbow. I just figured without some sort of fan or air pump there was no way that natural airflow was going to happen.

This pointed me to the Groco product; but it just seemed way overpriced for what it was. In deeper research I found a posting some guy did on a forum for trawlers who found this product and installed it in his boat's holding tank with very good results. My results have also been equally positive. I can now open up the inspection port with the tank full of product and the odor is really quite minimal. Before using this aerator, doing the same thing would knock you over with the smell. It is truly a night and day difference. To me this really proves your point about keeping the tank exposed to fresh air. The KO treatment also probably helps by introducing a nice dose of the good "bugs" - I believe this was a development of yours as well.

While the Marine Metal Power Bubbles may not be quite as refined as the Groco product in all it's details, I believe it gives essentially the same end result at a fraction of the price. The only slightly tricky bit with this unit is figuring out a clean and leak-free way of getting the hose inside of the tank. I personally have a tank I made myself (because of a tricky shape it needed to be) out of 1/4" plywood and fiberglass/epoxy. I drilled a hole in the top to tightly accommodate a short 1/8" diameter copper tube that I could push through and seal up with some good goop. This is the right size tube to push the hose onto. The pump also includes check valves to attach to the hose just in case the pump lost power and the tank overflowed, there should be no "product" going into the pump. Instead of a rigid pipe holding the aerator at the bottom of the tank like the Groco design, this system includes a small weight on the porous stone aerator to keep it from floating up.

Thanks again for all your advice.

Greg
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Old 25-10-2015, 02:58   #9
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Re: Aeration pumps for holding tanks

This is great, just the kind of chat I was looking for, thanks all.

Marine Metal Power Bubbles looks good. As its geared towards the fishing industry it may not be designed to run & run, but well worth testing at that price.

I too have had aquariums over the years and there is some real crossover of techniques and gear to look into, one thing that comes to mind are techniques using powerheads alternating to help reduce 'dead spots' etc etc.

Anyway, not wanting to detract too much from the rest of the chat, here is a rough sketch of the bellows/pendulum concept. As I said its just a concept to get the creative thinking going not an actual design.

The concept is to shift weight or liquid about, compressing air in the process, there are loads of ways, I think its worth thinking about.
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Old 25-10-2015, 07:49   #10
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Re: Aeration pumps for holding tanks

I'll give 'em a call on Monday, 'cuz I have a bunch of questions for 'em. There's a big difference between a live well and a waste tank... What's the lifespan of the stones in either? Will they become clogged with sludge and animal fats in waste? Replace or clean? If clean, how? If replace, how often? Are they the same stones used in aquariums? Stainless steel in contact with urine has very short lifespan...what are the alternatives? It would have to be able to run 24/7 on fishing boats offshore, but only for days. What about the 365 necessary to keep a waste tank aerobic?

I'll report back after I talk with 'em.
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Old 25-10-2015, 08:53   #11
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Re: Aeration pumps for holding tanks

I've used 12v aquarium pumps, identical to the Power Bubbles sort in year-long holding tanks tests. Works fine. All I did was run a tube to the bottom. I can't agree with the need for an air curtain, though I'm sure it helps reduce the air requirement in large tanks.

a. An over-size vent works, and there is no liquid circulation. This also demonstrates just how little air is needed.
b. There is no reason to run the pump 24/7. A few hours every other day should do, depending on tank size. The testing was based on a 10 gallon tank, 1 hour per day.
c. The tank will circulate with the boat moves.

There is no need to create a completely aerobic tank, just to support enough aerobic bacteria to consume the H2S and related compounds.

But basically, there are easier ways, discussed on this forum. Ventilation is simplest.
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Old 25-10-2015, 09:31   #12
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Re: Aeration pumps for holding tanks

? Why bother? Sail the boat, that will slosh things around
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Old 25-10-2015, 13:02   #13
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Re: Aeration pumps for holding tanks

A test of a 10 gallon tank on the bench only proves that passive ventilation above the surface works in small tanks...actually, up to about 20" in depth. Passive ventilation above surface can't supply enough oxygen to keep the contents aerobic below that depth...so when the boat rocks and/or the toilet is flushed, noxious gasses are pushed out the vent. Aeration solves that problem, and also eliminates the "blanket" of CO2 generated by aerobic AND anaerobic breakdown.

Preventing that "blanket" from forming is the reason it IS necessary to run the aerator 24/7 in a tank big enough to need aeration. If the contents at the bottom are allowed to turn anaerobic, that CAN be reversed, but it takes hours--even days in a large enough tank--during which time noxious gasses are being forced out, gradually diminishing over time.

It's actually very rare that tanks smaller than about 40 gallons need aeration to eliminate odor...UNLESS the tank is buried in a deep bilge and has a overlong convoluted vent line. In 90% of tanks passive ventilation above the surface is all that's needed.
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Old 25-10-2015, 16:02   #14
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Re: Aeration pumps for holding tanks

I should sell these things. Buy yourself a 12V bait tank aerator and run the aerator hose to a hose barb you fabricate in the top of your holding tank. Just buy a barb and drill and tap into the most suitable part of the tank top. That blows fresh air into the tank continuously. This is enough to stop the growth of anaerobic bacteria. Anaerobes are the stinky kind of bacteria.
Next fabricate a vent scrubber out of about 18 inches of PVC plumbing pipe with appropriate end caps and hose barbs, and if you want to be able to change the filtration material every year or so, make one end removable; fill it with activated charcoal granules from the pet store aquarium section, and slap your new scrubber into the tank vent line. Result: No holding tank odor, ever. And the parts are cheap.
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Old 25-10-2015, 18:23   #15
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Re: Aeration pumps for holding tanks

I have been using a fishtank pump, purchased at a pet store, for years now, and it has worked very well and small cost as well as very quiet.
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