Okay - so I am even more or less confused.

Your are now saying that we do not need two vents on a Baba 30
holding tank and one will suffice. I thought you said two were needed.

My logic says to use two vents, one in and one out and put in a small
fan powered by solar with a backup by battery and cycle it on and
off. Does anyone have a source for a simple dc fan that can bring in
air through a 3/4 hose?

I do not think I can run a straight vent hose as indicated.

Even though I was a physics teacher once and have an electrical
engineering degree, I guess I am just too dumb to figure all this out.

I guess Dave from the Baja is now convinced not to pump his tank dry.

Well back to billing time to pay for the shipping costs.

Alan


At 02:43 PM 1/5/2006, Peggie wrote:

>>...about the relatively low level of engineering and dispersed
>>scientific knowledge as to the subject.
>
> > I will just address a couple of issues:
>
>>(1) PUMPING THE TANK DRY
>>Anyway, my question should have been more clear: should a holding
>>tank not have a drain in the bottom to fully evacuate the wate from the tank?
>
>No. For several reasons: 1. it leaves waste sitting in the tank
>discharge hose. 2. It leaves any sludge in the bottom of tank ('cuz
>owners rarely if ever bother to flush it out of the tank) to dry out
>and turn to concrete, or to pile up in the line to the thru-hull and
>create a clog...or both.
>
>
>>(2) VENTILATION
>
>Alan, you're trying to over-engineer something that's actually very simple...
>>How does one increase the air flow through the vents of a tank?
>
>By increasing the diameter and making 'em as short, straight and
>horizontal as possible. When the tank location doesn't allow the
>vent line to be short, straight and relatively horizontal, or the
>tank is too deep for passive ventilation to work, either an
>aeration system that oxygenates the tank contents, or two vent lines
>with an exhaust fan in one to pull air through the tank is needed.
>
>>This is sort of black art (pardon the pun) - really, what is the
>>scientific principle that results in air flow. You need a pressure
>>differential. I do no understand how this is effective without a fan.
>
>You'll have to ask a physicists to explain it, Alan.
>
>>What about a solar fan?
>
>The source of power for a fan is immaterial.
>
>>How much air flow is needed - per minute, per day, per gallon, per
>>gallon per minute? How much oxygen is required?
>
>Not a lot. For instance, the Groco Sweetank air pump is only a 1.7
>litre/min pump, and is sufficient to oxygenate the contents of a
>tank up to 150 gals. The distribution of the air in the tank is more
>important than the volume.
>
>>Well, your responses below pretty much were non-responsive - but,
>>for my immediate need I am trying to decide how to increase air flow.
>
>For a tank the size of the one you're installing, you'll have all
>the air needed to keep it aerobic if you install a single 1"
>diameter (ID) vent line that runs forward no more than about 5', is
>straight, and doesn't rise more than 45 degrees, and use an organic
>tank product (Odorlos or Raritan K.O.).
>
>>Now I am confused. Earlier this week when I noted that that I was
>>going to installed a Sweetank, you pointed out how unsuitable it
>>was for a sailboat, would draw power, had to be kept on all the
>>time, and would clog up.
>
>I did not say that it was unsuitable for a sailboat...you inferred
>that it would be because it does need power 24/7/365. It will not
>clog up if it is left running continuously.
>
>>You then recommended no Sweetank and recommended an in and out vent
>>which is your standard recommmendation.
>
>I didn't recommend against it, I did say that I don't think you NEED
>it in a tank that small, especially since you intend to relocate the
>vent to the hull.
>
>> But, you could not say how really to assure air flow except not
>> to have a vertical vent (which our beloved Baba 30's have) and to
>> have two. So, I wondered if there was a simple in line fan.
>
>You won't need a fan, Alan...nor will you need two vents.
>
> > I guess no one wants to fund
>>a study as to how much air (cubic feet) needs to be blown into a
>>closed holding tank over each 24 hours (taking into account
>>temperature, surface area, volume of waste, type of waste. air
>>flow) in order to keep the tank fresh. Surely the studies are there.
>
>Yes they are. There's no need for any studies specific to holding
>tanks because the same principles apply to storing toilet waste and
>flush water in a tank that apply to the storage of any other liquid
>in a tank. And the same principles re the breakdown of ANY organic
>matter, both aerobically and anaerobically, also apply to the
>organic matter in a holding tank. In fact, you should be able to
>extrapolate all the information you think you need from any source
>that deals with keeping an aquarium aerobic...the contents of a
>holding tank are about the same density and pH level as water, and a
>tank is a tank.
>
>>Which goes back to my initial issue which was putting in a
>>SweetTank and running it on a timer - but, then I would have to
>>know whether a few hours a day is all it takes.
>
>That would vary depending on temperature. Bacterial activities
>increases as temperature rises, decreases as it falls. Above about
>78 F, the increase is exponential...below 60 it becomes very
>sluggish...increasingly so till it ceases altogether below 40 F. So
>while you might get away with running it for only a few hours a
>day--or even leaving it off for days--in the spring and fall, it may
>or may not be necessary to run it continuously in July and
>August...depending upon how warm it gets inside your boat sitting in
>the summer sun. But again, Groco does not recommend leaving it off
>because unless air is being blown out of the "perforations" (for
>lack of a better term) in the piping to prevent it, sludge can
>settle into 'em and clog 'em up.
>
>It's not rocket science, Alan...nor is there anything about holding
>tank maintenance that's arcanely specific to holding tanks. It's
>just another application for a few VERY simple bio-chemistry principles.
>
>Peggie
>
>>
>>>Alan Sugarman wrote:
>>>
>>>Thanks for the images!
>>>
>>>>As to the EPA etc., there are government grants out there for this issue.
>>>
>>>
>>>Only for pumpout equipment, nothing else.
>>>
>>>>Government funds have gone to funding pumpout stations etc. - it
>>>>would make sense for some funding of technology advances in the
>>>>sanitation area. What kind of research could be done with EPA,
>>>>State, or Boat US Foundation Grants:
>>>
>>>
>>>
>>>>Examples:
>>>>Should holding tanks be pumped dry?
>>>
>>>
>>>That requires a grant? Otoh, somebody did get one to study why
>>>kids fall off tricyles (conclusion: because they lose their
>>>balance)...so why not? Maybe I'll apply for one...:)
>>>
>>>>How does one increase the air flow through the vents of a tank?
>>>
>>>
>>>Already known.
>>>
>>>>Miniaturization of pumps?
>>>
>>>
>>>They're already about as small as they can be to efficiently
>>>handle flow through 'em at a rate that wouldn't have you pumping
>>>for an hour to move 5 gallons.
>>>
>>>>Development of electrosan type units so that the processing unit
>>>>is separate from the holding tank?
>>>
>>>
>>>Apparently you're not familiar with the Lectra/San and how it
>>>works at all. It already IS separate from any holding tank...it's
>>>a flow-through system that treats and discharges a flush at a
>>>time. There are other Type I and II systems that are designed to
>>>be connected to a holding tank...Galley Maid, HeadHunter, the
>>>Groco ThermoPure are just few.
>>>
>>>>Air ventilation pumps?
>>>
>>>
>>>Already on the market...the Groco Sweetank was the first (and
>>>still the best by far), but it has competition.
>>>
>>>>Separation of urine and flush water from fecal matter?
>>>
>>>
>>>Already on the market...take a look at the AirHead--which is a
>>>dessicator--and composting toilets. However, they still leave you
>>>with the issue of what to do with the urine. It has to be drained
>>>off, or the solids won't compost, they'll just rot and stink...and
>>>you can't legally pour just urine overboard inside the "3 mile
>>>limit," so you have to store it aboard--either in jugs or a
>>>tank--and either carry 'em off the boat or have the tank pumped
>>>out. So I don't see much advantage to 'em.
>>>
>>>Re tank venting...
>>>
>>>>This is sort of black art (pardon the pun) - really, what is the
>>>>scientific principle that results in air flow. You need a
>>>>pressure differential. I do no understand how this is effective without a fan.
>>>>What about a solar fan?
>>>>How much air flow is needed - per minute, per day, per gallon,
>>>>per gallon per minute? How much oxygen is required?
>>>
>>>
>>>There are no "one size fits all"/"cookie cutter" answers to those
>>>questions...it depends on the tank location, size of the
>>>tank--especially the depth, length and diameter of the vent line,
>>>lcation of the vent thru-hull...
>>>
>>> > Lectra/San is $999 at West and I still need a holding tank and a salf
>>>
>>>>feed system at $400.
>>>
>>>
>>>You're shopping at the wrong store..WM's prices are the highest in
>>>the country! You can beat their price by at least $200 if you shop
>>>hard. The PuraSan, which doesn't need salt, can be found for under $700.
>>>
>>>>Sweetank is $250.
>>>>Shipping a tank from UK is maybe $125 if that much.
>>>
>>>
>>>Plus the cost of the tank. And don't forget the tank level
>>>monitor. CG regs require some means of determining when the tank
>>>is at least 3/4 full. If the tank is readily accessible for visual
>>>inspection, no gauge is needed...but if it's not (which is
>>>unlikely under a v-berth), you'll need one.
>>>
>>>>Anway, the Lectra/San is 13.5 inch high due to its inflexible
>>>>design which has not changed in years and years.
>>>
>>>
>>>Actually it has been, internally, several times...and the new
>>>Electro Scan is a completely new design.
>>>
>>>There's a LOT more R&D going on in the marine sanitation industry
>>>than you think there is, Alan...none of it gov't funded either.
>>>But there are limitations to what's possible. Some of your
>>>expectation are tantamount to expecting an engine mfr to develop a
>>>40 hp diesel that'll fit in a shoebox. If you do a little
>>>homework, you'll learn that there are good reasons why pumps,
>>>y-valves, etc are the sizes they are.
>>>
>>>--
>>>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/store/customer/product.php?productid=40&cat=6&page=1
>>>
>>>http://shop.sailboatowners.com/books/detail-books.htm?fno=0&sku=90&cat=1304
>>>
>>>
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>>
>>
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>
>--
>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://shop.sailboatowners.com/books/detail-books.htm?fno=0&sku=90&cat=1304
>
>
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Received on Thu Jan 05 13:12:58 2006