Holding Tank Odor and Filters

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thinwater
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Holding Tank Odor and Filters

Post by thinwater »

I'm starting some research for Practical Sailor, in part because I was asked, but the deciding factor was personal need. I found a few PDQ forum posts about the Sealand/Dometic filter, but nothing more.

Yes, I have tired many treatments over the years. They help some, but not enough, and I'm lazy about them. And that isn't what the article is about.

The vent location on the 32 is poor; it's forward and if you are anchored it's going to come in.

I'll be testing a number of brands using "synthetic" holding tanks. I'll also be exploring some DIY alternatives and improved installation, so that they cannot be damaged by overflow or contribute to sucking a tank in. I've designed commercial odor control systems, so I do have a firm grasp of the chemistry.

Any PDQ Altair-specific expereince? I'd hate to start in the wrong direction.
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Re: Holding Tank Odor and Filters

Post by Mongoosemagic »

I know that you said that your article was not about additives.....But, I had the same problem to the point it was uncomfortable to sit on the tramp. I read a book (Getting Rid of Boat Odors) and the reccomendation was for K. O. (Kills odor) and C.P. (Clean Potties) both by Raritan. I tried them and they do work. The upkeep is very minimal, add K.O. when you have your tank pumped and only use C.P. to clean the head. We have left the boat in the sun for a month with a half full holding tank, and have not had any odor. We also have spent the winter in the Bahamas and another winter in Florida without any odor so the products work without any need for a filter. We have hull #36 (Mongoose Magic)
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Re: Holding Tank Odor and Filters

Post by thinwater »

My publisher just expanded the scope, so I will be looking at chemicals too, using the same set-up. In that way we can make some direct comparisons. Certainly, KO was on the list.

Anyone no of chemical approaches that are not so well known, or perhaps self-formulations?
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Re: Holding Tank Odor and Filters

Post by eepstein »

I don't have any secret formulas, but have used vinegar. I also heard someone uses Epson salts to bring the salt level in the holding tank to a toxic level. Never tried it myself though. Let me know if you need assistance. I'm on the hard at Herrington (row J).
Eric & Bonnie Epstein
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Re: Holding Tank Odor and Filters

Post by Page 83 »

http://forums.hunter.sailboatowners.com ... y.php?f=31

This is the Head Mistress blog, Peggy Hall. Look here first.

When I bought my 32 I was told that the vent hose was too small, and made matters worse. At that time Forum Wisdom was to go to a 1" id vent hose and fittings.

On another forum there was discussion of pumping air into the sewage with a glorified acquarium pump. I don't know where that idea went.

I'm not sure whether or not smells will go away if you kill active culture in the sewage. It seems that encouraging the little buggers might be a better idea. I'm not even sure which little buggers are aerobic vs. anaerobic or which is desirable.
Sandy Daugherty "Page 83" PDQ 36026
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Re: Holding Tank Odor and Filters

Post by SecondWind »

ODORLOS, sold at West Marine. Never a problem after we started using it.
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Re: Holding Tank Odor and Filters

Post by thinwater »

Page 83: Hi!

Yes, I have spoken with Peggy off-line. She had some sound advise that will be incorporated into the experimental design. We will be testing many combinations.

Regarding the aerobic/anaerobic bug thing, I will be testing that in a practical way by varying the vent size. Wastewater plant design is part of my work (industrial not sanitary) and some of those plants use bugs and some have odor problems anyway. We treat these with improved aeration and a variety of treatment systems. She absolutely is right when she says aerobic systems stink less, but the question is what is practically achievable with common levels of benign neglect?

Theories are great. Side-by-side testing sorts them out. My job is to keep an open mind, listen to EVERY comment, and try to incorporate as many experiences and questions as practical.
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Re: Holding Tank Odor and Filters

Post by Page 83 »

This is beyond the scope of your article, but I've wondered if a very simple bellows could pump a bubble or two into the holding tank just from wave motion. It would be great to find out how much air is required, and if it needs to be distributed evenly through the tank.

Call me if you need help assembling stuff. I'm good at generating stink. (410) 956-2331
Sandy Daugherty "Page 83" PDQ 36026
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Re: Holding Tank Odor and Filters

Post by thinwater »

My final solution; A carbon filter with a slightly convoluted installation. Cheap, though.

http://sail-delmarva.blogspot.com/2011/ ... ilter.html

The PDQ 32 has a TERRIBLE vent location and I think this may be a good answer for the 32s only. So far, fresh as a flower.
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Re: Holding Tank Odor and Filters

Post by amytom »

Drew,

I'm attempting to copy your design, (greatest form of flattery?) and had a few questions:

1) Would mounting the unit vertically prevent the settling of the carbon issues?

2) Would it be beneficial to make the housing out of clear PVC to view the contents?

3) How deep of a loop would be appropriate to ensure some liquid stays in there while still preventing overpressure or vacuum? I was considering a loop dropping two feet beneath the filter.

Thanks for your thoughts,

Tom
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Re: Holding Tank Odor and Filters

Post by thinwater »

I'm not too flattered; the filter is boring in concept and running traps is traditional bathroom plumbing. But so far it's working perfectly.

1. If I had had space, vertical orientation would be good. I preferred to have it higher, so that overflows could go under and out the bypass. However, vertical mounting is not required: tap the carbon down and pre-load both foam supports by compacting them a bit. That is how the manufacturers do it.

2. Spent carbon and new carbon look exactly the same (I've emptied many industrial canisters, holding thousands of pounds). It wouldn't hurt anything, but I don't think it would help. I do like the idea of having the trap loop clear, because you do need to keep liquid in it. I may switch to antifreeze, since it won't evaporate; I'll have to see if that is a problem.

3. I don't think a loop need be anymore than 6-8 inches. I have an 8-inch loop and I have observed it during flush and pump-out cycles; it does not move more than a fraction of an inch. The pressure drop through the carbon is quite low, if kept dry. Sailing, even in rough water (25 knots, steep chop) does not seem to splash the loop much. It stayed full. Too deep a loop and the by-pass function is defeated.

4. If you don't want to get fancy on the mounting, I think 2-inch PVC conduit clamps would do a nice job; they fit the pipe perfectly, but would need a spacer under them to allow clearance for the fittings. Two ~ 1/2" x 3/4" x 3" strip of wood or Starboard would do nicely and would be lighter and simpler. I think I was just bored and wanted to do some woodwork.

A few interesting tidbits. I am currently doing a long-term study of filters and hoses for Practical Sailor (I have 6 small holding tanks in my back yard--ew), and I've learned a few things:
* All of the filters hold about the same amount of carbon. There must be little point in being larger... or they just copied each other.
* Everyone I have talked to indicated they last 2-5 years.
* Some designs are meant to be screwed to the tank (Big Orange, Vetus) while other suggest mounting high (in the Dometic instructions and over the phone). Yet Dometic mounts theirs on the tank if you buy a complete system. It seems they are like to rely upon frequent pump-outs or monitoring systems.
* The best deal on hose barbs was from "Best Deal" hardware (which makes for a ridiculous sign in Deale, Md).
Writing full time since 2014.
"Rigging Modern Anchors,"Seaworthy Press, https://www.amazon.com/Rigging-Modern-A ... 1948494078
Book Store. http://sail-delmarva.blogspot.com/2017/ ... store.html
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