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Old 03-02-2011, 09:03   #1
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Proper Holding Tank Positioning

Hi everyone.
Im ready to install this new holding tank, but it will only fit in one place and it would have to go on its side. I'm just wondering if it will work properly if the in and outlet are both on the side of the tank and not the top. It sits well bellow the head where I would plan to install it. Any thoughts or advice greatly appreciated. (Picture of the tank bellow. That's what I mean by "on its side")
I would really like to avoid the relocation of the fittings on the tank!

Thanks to all for looking.
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Old 03-02-2011, 09:20   #2
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The pump out port has to be on the bottom (not underneath, low side) unless it has a dip tube in it, then it has to be on top. The vent preferrably will be fore or aft. The holding tank that was in my boat when I bought it had the vent located on a side, facing the side of the boat, and the morons ran the vent line down then up. So had just pumped out the night before, tank mostly empty. Went sailing heeled over. Someone uses the head and the vent mounted on the deck spews good stuff. Heeling the boat put liquids in the vent line that since it went downhill collected a slug of it, next use of head clears the vent line onto the deck. They also plumbed the head outlet to the bottom fitting so they could turn the Y valve to the 3rd position and let gravity drain the tank. Problem with that is the hose from the head to the tank is always full of sewage. The hose was half way clogged with settled sewage that had turned to concrete.

I replaced the tank with one with all fittings on top so I don't have to worry about leaks or vent lines filling before the tank is full. Many boats don't have the space luxury for this.

John
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Old 03-02-2011, 09:42   #3
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Even if the vent faces aft or forward, you absolutely MUST run the vent line up immediately before it goes horizontal.
Wave action of the boat will do what was previously posted.
That pic looks to me like the vent is going to give you a repeat performance the first time you're punching into a sea with even a partially full tank.
Sloshing will find that vent line.
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Old 03-02-2011, 10:06   #4
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So probably best to relocate the fittings, or make the tank fit upright I guess? There is actually one place where the tank would fit well up right. Plus there would be ample space for all the plumbing, but the tank would actually sit higher than the head's outlet by about a foot. Is that a bad idea? I have a vented loop and everything.

Thanks
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Old 03-02-2011, 10:13   #5
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Never, Never , Never, install a holding tank with fittings below liquid level, this is sewage you are dealing with, think about the future when you may have a problem!
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Old 03-02-2011, 10:39   #6
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Quote:
Originally Posted by Amigo View Post
So probably best to relocate the fittings, or make the tank fit upright I guess? There is actually one place where the tank would fit well up right. Plus there would be ample space for all the plumbing, but the tank would actually sit higher than the head's outlet by about a foot. Is that a bad idea? I have a vented loop and everything.

Thanks
Here's a proper holding tank design.

http://www.sealandtechnology.com/pdf...12%20BASIC.pdf

Above the head is ok if you have a properly operating vented loop.
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Old 03-02-2011, 11:09   #7
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It's too bad that you've already purchased the tank. They come in many different sizes/shapes with the fittings installed where you want them.

I'm installing a custom V-tank all the way forward in the bow, which will run the same amount of hose as it has now.

http://www.raritaneng.com/pdf_files/...nk/L165htw.pdf
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Old 03-02-2011, 11:11   #8
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Never, Never , Never, install a holding tank with fittings below liquid level, this is sewage you are dealing with, think about the future when you may have a problem!
My tank is exactly like yours, 10 years now , no problems.

Dave
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Old 03-02-2011, 12:17   #9
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Proper Holding Tank Positioning

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This is a 37 gal. tank installed in a Cal 29. Most things are possible when you think about it

JB
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Old 03-02-2011, 20:48   #10
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1. Its better to have all the fittings on the top (no leak issue possible) , and its cheap to relocate them. So unless the fittings will not fit on the top, relocate.
2. Its actually a good idea to have the holding tank higher than the head. In fact if the holding tank is above the heeled waterline of the boat, you do not need a vented loop in the outgoing hose (from the head to the holding tank nor from the holding tank to the through hull). Your vent line makes your entire tank a vented loop!. plus you can then have the holding tank gravity-drain.
3. To avoid having waste sit in a hose, flush every time sufficient so that the hose from the head to the holding tank does not hold any waste, only water. The heads I just installed (Raritan Elegance) use 1" sanitation hose for the outlet. I connected the 1" hose to a 1" pvc running to the top of the tank where it emptied. 1" hose holds a lot less fluid than 1 1/2 " so with a given flush volume less waste is hanging out in the sanitation hose

The simplest system is to have the holding tank above the waterline; run the vent from the top; run the hose/PVC from the head to the top of the tank; have the pumpout also running from the top of the tank (tank-depot.com sells a great fitting for this); and have the outflow from the bottom of the tank directly to the through hull with a simple ball valve on the bottom of the tank, so that waste does not sit in the discharge line. no y valve. No vented loop or macerator needed.
see Calder's book on mechanical and electrical systems where he makes the case for this setup.
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Old 04-02-2011, 13:10   #11
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3. To avoid having waste sit in a hose, flush every time sufficient so that the hose from the head to the holding tank does not hold any waste, only water. The heads I just installed (Raritan Elegance) use 1" sanitation hose for the outlet. I connected the 1" hose to a 1" pvc running to the top of the tank where it emptied. 1" hose holds a lot less fluid than 1 1/2 " so with a given flush volume less waste is hanging out in the sanitation hose
You do have to remember that old rotten seawater (dead creatures) can smell too. For storage it's best to run fresh water (pour in a bucket full) and flush dry as possible.
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Old 04-02-2011, 14:13   #12
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This mostly applies to multihull's narrow hulls, but:

We had an unusual situation. The bow "head" portion of our trimaran's hull is very narrow. It is the only appropriate location for the head as well. So I built the 30 gallon holding tank out of the hull itself. Protected with three layers of 10 oz fabric, and well "gel coated" with 8 coats of pigmented epoxy.

When the head floor = tank lid, was glued down, it included a clean out "O" ring deck plate, anti slosh baffle, head mounting pedestal on top, pumpout PVC tubing, and hosebarb, as well as a shower water sump and vent through hull.

It has worked perfectly with our Levac head for 15 years now. It would otherwise have to be located quite remote from the head, rather than under it, thus requiring more flush water. M.
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Old 04-02-2011, 19:16   #13
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Beware Vented Loop Odor

It took me years to figure out that the stink I couldn't get rid of was coming from the vented loop and not the hose or elsewhere.

Wave action will cause the seawater level in the overboard line to rise and fall. On the fall the vented loop will let air in and on the rise the air in the hose will pressure. So now the stinky air in the hose is under a little pressure and over time it slowly seeps out past the vented loop checkvalve into the cabin.

The other problem this backpressure causes is that the macerator pump will not prime reliably.

The fix in my case was to redesign the system to not need a vented loop but I think you could also use a hose on the vented loop to overboard. Some vented loops have fittings for just this. I also switched to a diaphram type pump. Ten years later, no problems.

I also highly agree with other posters that you want hoses to go in and out of the top of the tank. One day you will have to open up the system (a clog?) to fix something and you gotta be able to do that with stuff in the holding tank.
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Old 05-02-2011, 01:07   #14
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well thanks a bunch to all of ya!

I'm pretty sure I am going to be able to make the tank work up-right. But I have a good reference list of points to consider before the final install.
The the crazy rules head plumbing.....

Thanks everyone
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Old 05-02-2011, 02:11   #15
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simple?
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