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Old 12-11-2004, 02:14 PM   #1
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Design review

The welder couldn't work Friday due to the weather here. So I reviewed the frame work and changed the design of the waste water system.

I found a marine holding tank thats 44x26x6. This would be under the rear of the trailer allowing a direct drain from the shower/tub, sink, and toilet. A marine mascerator pump would move the water into a larger above floor tank as needed for extended say or to travel if no dump was handy. How does one install the toilet in a tank. I suspect it's not to different from household but don't know. Would the 3/4 ply be a problem in connecting the toilet to the tank (yes I know I need to put a hole in the floor ). In order to reduce the chances of tearing this think off backing into some sloping site or damage by road junk I was thinking of having a 10gauge? or so box bent and welded to the crossmembers. That should hold it well with some rub rails to support it. What do you think.
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Old 12-11-2004, 04:59 PM   #2
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Quote:
Originally Posted by Over59
The welder couldn't work Friday due to the weather here. So I reviewed the frame work and changed the design of the waste water system.

I found a marine holding tank thats 44x26x6. This would be under the rear of the trailer allowing a direct drain from the shower/tub, sink, and toilet. A marine mascerator pump would move the water into a larger above floor tank as needed for extended say or to travel if no dump was handy. How does one install the toilet in a tank. I suspect it's not to different from household but don't know. Would the 3/4 ply be a problem in connecting the toilet to the tank (yes I know I need to put a hole in the floor ). In order to reduce the chances of tearing this think off backing into some sloping site or damage by road junk I was thinking of having a 10gauge? or so box bent and welded to the crossmembers. That should hold it well with some rub rails to support it. What do you think.
3/4 inch plywood will pose no problem for you, the attachment is the same as a house. I like your box idea for protection, some trailers have an above floor tank below the toilet, so I wonder if you could not raise the tank just a little so the protection will not be needed. It would not be above floor completely, but would not protrude under trailer at all.
This would of course raise the toilet the same amount.
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Old 12-12-2004, 06:30 AM   #3
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Standard rv installation would have threads for the toilet floor flange screwed into a bung in the top of the tank. The flange is screwed to the floor, make sure you give the toilet a test fit. There is some adjustment, but only some.

10 Ga is pretty heavy metal, 16 or 18 would be better IMO. The frame isn't really built for a lot of weight, if you get into a situation where you can't dump and have to move the trailer with the tank full it that is a lot of weight. Plus this is weight off the gvw that you will never get back. I would also turn the skids so they run front to rear, less chance they will get ripped off if they do drag. Bolt the box to the crossmembers, if it is welded and the tank has to come out for some reason the choice for removal will be cutting the welds to get it out the bottom or removing a secton of floor, cabinetry, walls to get it out the top.

An auxillary tank will take valuable interior storage that you will never get back. Any drain fittings (leaks) will be above the floor and inside the trailer; again there will be more weight. This is a trade off between storage and holding tank capacity, which will you need more?

There are outfits that make custom tanks. If you can keep it above the belly pan that gives you more ground clearance and less chance of contact. Thetford makes a short toilet which will sit on a platform above the floor, I would look at this option also.

John
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Old 12-12-2004, 08:21 AM   #4
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I think I'll make a few adjustment.

We have stuff in the Caravel we never use. The design principle at work here is 10 days off grid and no blueboy mess. I'm putting in 2 55 gallon (46x20x13) holding tanks over the axels next to the wheel well. These would travel empty or to the next dump station. Prehaps I should keep "wash water" and black separate. Those marine electric toilets are expensive. $$$$ but pump directly into a holding tank.

What's a bung?
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Old 12-12-2004, 08:37 AM   #5
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What's a bung?
The sidewalls of the tank are relatively thin. There will be a thicker piece for the threads, like the opening in a barrel. Not really sure that the tank builders call it, that was as close as I could come.

John
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Old 12-12-2004, 09:35 AM   #6
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1000 lbs!!!

Quote:
Originally Posted by Over59
I.....I'm putting in 2 55 gallon (46x20x13) holding tanks over the axels next to the wheel well.......
110gal. X 8.3 lbs/gal. = 913 lbs + tank weight = at least 1,000 lbs.

Wow.
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Old 12-12-2004, 12:34 PM   #7
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Will rarely if ever fill em and still looking for something in the 40 gallon range that will fit. Maybe a week at a site that has water and electric but no sewer hookup like some of the state parks and dump on the way out. I'll carry 70 gals fresh water so that's the limit on a dry site. There is no way my wife will dry camp for 7 days on 30 gallons of water.

The space between the wheel wells under the beds is difficult to use without complicated cabinet skills. Aft of this will be batteries on curbside and water heater on the other and pumps.

The trailer new was 3250#. I will at least put on new axles, hubs, ect. Maybe new Flex axles with dics brakes all around for going down mountains.

After the floor's in I'll take it to the scales. Give me a good starting point. I want to be 4250# ready to go.

I don't understand how a 24 Gallon tank weights 70lbs but that's what it says. They want $55 to ship. I'll look for a local option. The 55's are only 35lbs and I can pick them up.
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Old 12-12-2004, 09:56 PM   #8
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40 gallon tank...

I am intending to use a 40 gallon tank as both a grey and black water tank. I am leaning in favor of one that is actually intended as a fresh water tank and is basically rectangular with no slope to the bottom of the floor. I know that this may be a little harder to drain but I might also mount it with a slight slope toward the end where I intend to put the drain. I found one that measures 20" wide, 54" long and 9" tall that contains 40 gallons. There is a mail order RV supply house near me that actually has that size in stock. The current price is $222.00. There would be no shipping charge for me. I have found similar sized tanks at other vendors for less money but with the shipping charges it is pretty much of a wash price wise.

At any rate I intend to mount my tank under the floor in the space just aft of the second axle. I have about 5" of space in the belly pan and the tank will hang down about 4". It turns out that my axles hang down 3-1/2" to 4" as well. I do not want to rely on the frame cross members in that area to carry the weight of the tank so I am thinking of using a couple of pieces of preasure treated 2 x 6 lumber cut to fit. It turns out that the 20" width of the tank plus the 3" of width of the wood (1-1/2" each) will be a pretty good fit between the cross members. The wood will also insulate the tank on both sides. I am going to have a sheet metal pan made up that fits the tank with enough room to add 1/2" of polystyrene insulation board around the tank bottom. The attached sketch shows the general idea. I will run the belly pan over the 2 x 6 first and then secure the tank pan using lag bolts screwed vertically up into the wood cross members. If the sheet metal pan seems a bit flexible I will add a stiffener strip of some sort along the edges of the pan. I know it is wood that I am adding but it should be strong enough, reasonably light, has insulation value and does not require any welding to istall.

If you want to pump fluid to above floor tanks consider just adding a macerator pump. They are a lot less expensive than adding a marine macerator toilet. I found one for $152.95 at the same place that carries the tank.

Here is the RV supply place where I found the tank and pump. Just check out the index. The tank is under "water tank" by the way.

www.rvpartsoutlet.com

Malcolm
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Old 12-13-2004, 11:33 PM   #9
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Change of Plans

A one tank solutions doesn't work. Should it get full the shower drain would be full of tank liquid. At six inches high and a 1.5 opening my effective tank depth would be 4.5 inches.
Two tanks. The shower drain is 14 inches from the back of the trailer. The cross member is 1.5" plus .5 for clearance. Thus the available space aft of the crossmember is 12". The toiler outlet is center 11" from the wall with a 3" opening which means the edge of the tank has be extend to 13" from the wall which is 1" more than is available.
New design.

Toilet tank 10 gallon 32x19.5x4.75 on top of floor with 1.5 opening and mascerator pump to "central storage". Crossmember (10gauge) at 12" from rear right under the rear tank. Remove the next member which is 2' from rear and add new one at 3 plus'. Creating a new 26 x 54 space for the 24gal shower / sink tank. Both tanks will extend under the vanity (curbside wall) for easy top venting to original vent. Rear support when parked will be necessary and I still have to move the water to the above axle tank to travel but I may now go with one 55 gallon or two 35's for "central storage" tank. That would give me ~90 or 105 gallons parked capacity.

So, what do you think. Welder comes Friday.
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Old 12-14-2004, 12:57 AM   #10
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Over59,

It sounds like it should work unless the total weight with full tanks for travel is too much. How will you make sure that you have enough capacity in the mid tank(s) to move all the fluid from the rear before hitting the road?

If you are intending to use a macerator pump to move fluid from the rear to the mid tank(s) then it seems like one tank in the back could work as long as you made sure you pumped it out before anything overflowed. You can get a 1-way valve that would prevent back flow into the shower. I think it would prevent the shower from draining until the tank was pumped is all. In my case I can get away with one tank for the shower because of my plan to put radiant heat on top of the regular floor. I will have just barely enough space on top of the frame to get the shower drain to come into the top of the single holding tank rather than into the side. Check out the following thread and especially posts 20 to 23 for some discussion about one-way valves and where to find them:

http://www.airforums.com/forum...ad.php?t=12785

Malcolm
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Old 12-14-2004, 07:56 AM   #11
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I do not want to rely on the frame cross members in that area to carry the weight of the tank so I am thinking of using a couple of pieces of preasure treated 2 x 6 lumber cut to fit. It turns out that the 20" width of the tank plus the 3" of width of the wood (1-1/2" each) will be a pretty good fit between the cross members. The wood will also insulate the tank on both sides. ........... I know it is wood that I am adding but it should be strong enough, reasonably light, has insulation value and does not require any welding to istall.
Just a couple of thoughts- wood is porous, if you have a leak it is going to be a really nasty mess to deal with. Even pressure treated wood will split and eventually rot. The split is going to run with the grain and you are already loading it vertically. I don't know the insulation value of wood, 1 1/2" can't be very high. If it is wet from the road or waste it has to be a lot less. AS typically heated their tanks, it definitely is a necessity in many areas. My heat runs through the tank surround and then to the bedroom. That could be a source of odor if the tank did leak and contaminate the wood.

John
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Old 12-14-2004, 12:47 PM   #12
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John,

You raise some good points about the wood and its porosity. Exactly the same reasons I am going with Polyboard for my floor replacement. There are structural varieties of plastic lumber that I could look in to. My general observation has been that plastic is usually heavier than wood but it might have a higher R value. I guess I could add some additional steel there instead. I had actually also been giving some thought to using thinner material than the 2x_ and letting the foam insulation go all the way to the top of the tank. I will have to give it some more thought. I think wood has an R value of something like 1 to 1.5 per inch by the way. While that it not a lot I was thinking that just a modest amount of insulation was needed for the task.

Thanks for the feedback.

Malcolm
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Old 12-15-2004, 10:23 AM   #13
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A designer's work is only done when the job is finished.

After pricing tanks, toilets, pumps, ect. And counting connections I am returning to the design table. Check this pump out. With this I don't need any tank in the back if I use a marine electric toilet. Over all cost about the same and few connections to worry about and the cabinet work and insultaion is easier. Nothing hanging under the tailer either.
Shower pump http://www.defender.com/product.jsp?path=-1|51|26832&id=121239
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Old 12-15-2004, 12:52 PM   #14
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Over59,

I think you are on to something here. If you really do want to have remote tank(s) over the wheels this looks like it could be a really good solution. I would suppose that it could handle the bathroom sink as well as the shower. The site that you pointed to has a qood variety of marine toilets to choose from too. I am still a bit puzzled as to why they seem to be so expensive. The same site carries a stand-alone mascerator pump for about $110. Why does adding the pump to the toilet seem to make it more expensive that a standard toilet and a stand-alone mascerator pump? I also noted that there are some marine toilets that have a manual pump. There was even a Porta Pottie brand unit that has a small 9 gallon above floor tank built in. I suppose that it would be possible to use a regular macerator to empty the 9 gallon tank to the central holding tank.

Are you contemplating having the central holding tank(s) be seperate for grey and black water? I will be interested in seeing what you finally come up with.

Malcolm
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