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Old 05-14-2007, 04:41 PM   #1
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1976 27' Overlander
Hackett , Arkansas
Join Date: Nov 2006
Posts: 21
black water tank for '76 Overlander

I am currently in the process of renovating a 1976 Airstream Overlander and have run into some problems with the black water holding tank. It appears that the previous owner may have failed to unhook the hose before driving away from the campsite. The neck of the tank between the body of the tank and the valve is cracked causing the tank to leak when it becomes full to a certain point (bad smell and moth flies!). I'm afraid that any repairs made to the neck will only break once the tank becomes full again. Replacing the tank is probably the best option. Any suggestions for locating a new tank or learning the exact dimensions of the original tank before removing it? What is the best way to remove the tank on a '76 Overlander? Will the gray water tank have to be removed also? Any thoughts or suggestions will be greatly appreciated.

Dennis
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Old 05-14-2007, 04:53 PM   #2
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1993 21' Sovereign
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According to the 1974 service manual, and the 1977 service manual I have, the black and grey tanks come out through the belly pan at the rear of the coach. You should not have to remove the black tank to remove the grey tank, and their brackets are hinged at the front so when you unhook everything, only the rear of it falls on your head. From what the service manual says, black tank is 20 gallons, grey tank 10 gallons.
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Old 05-16-2007, 02:55 PM   #3
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1976 27' Overlander
Hackett , Arkansas
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Thank you for the information Terry. The belly pan at the rear of the Airstream appears to be bolted in place. I am guessing that the bumper should be removed and then the bolts must come out. Will the sheet metal require any cutting? I think that I will just remove the old tank, take its dimensions, and then have a new one made. I'm sure the original Thetford valve will need to be replaced also.
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Old 05-16-2007, 03:07 PM   #4
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1993 21' Sovereign
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According to the service manual for the '74 (I've put away the one for the '77 for the move), you have to drill out the rivets to get the piece of bellypan down, then remove the various pieces so it will drop down.
I can try to scan the page, and email it to you this evening, if you will send me your email address.
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Old 06-11-2007, 02:19 PM   #5
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1976 24' Argosy 24
Milford , New Jersey
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Dennis, How are you doing with your project? I think i face a similiar fate with my 76 Argosy. Was wondering if you have any pointers? George.
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Old 06-11-2007, 02:45 PM   #6
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1976 27' Overlander
Hackett , Arkansas
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Hello George- I have managed to remove the back bumper and the belly pan. Most of the bolts were rusted and consequently broke while I was removing them. I will have to clean up all of the rusted metal and probably replace some of it before I go much further. I have not removed the tank yet, but it appears that all I need to do is detach the tank from the toilet, the vent pipe, and the outlet pipe/valve and it should come right on out.

The only damage to the tank is around the neck, close to the valve. I am going to try and find a company that can repair the original. Any ideas? Is your damage in the same area?
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Old 06-12-2007, 12:04 PM   #7
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1976 24' Argosy 24
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I would probably try to replace the tank if finances allow. it's alot of work your going through and if the repair doesn't last your going to have to do it all over again. Just my opinion, I'm sure there are ways to repair it, but for how long? George
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Old 06-12-2007, 12:14 PM   #8
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1973 27' Overlander
'Possum Holler , Georgia
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Dennis, on my '73, the fresh water tank was damaged (because of my, uh, unskilled use of a skill saw). I took it to the local RV center and they were able to repair it by "welding" the plastic closed. The black water tank is made of the same material on mine. You might give that a shot first.

The new tanks are limited in supply (originals, that is) and are quite expensive. The repair on my fresh water tank cost ~$90, versus about $500 for a new one.

Let us know how it turns out.

Jim
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Old 06-14-2007, 12:59 AM   #9
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1976 27' Overlander
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I removed the black water tank today and realized that it cannot be repaired. Not only is the neck busted, but there is also a large crack around the threaded area on top into which the toilet is mounted. I may just have to buy a new one. Where might a new tank be purchased? Any suggestions?

Also, I was reading about this is another thread. Is there a proven way to bypass the black tank entirely and deposit waste directly into the waste site? It seems like one might be able to just run a 3" sewer pipe from the toilet to the pipe and just dump the waste it into whatever septic system. Of course, this might be an obstacle on the road, but it might also eliminate some potential problems.
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Old 06-14-2007, 06:09 AM   #10
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I found that, for the fresh water tank, it would have been cheaper to have a local sheet metal shop build a brand new, stainless steel tank, than to purchase an off-the-shelf replica of the original. Yes, there's added weight, but the trade off is that it will probably last forever. And you can reduce weight by making the tank smaller and moving other heavy items out of the back of the camper (battery, Univolt, etc).

Just another option.

Jim
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Old 06-14-2007, 10:14 AM   #11
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Thank you Jim. I'll check into that as an option. I'll look at the prices on some originals also- if I can find any.
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Old 06-15-2007, 10:56 AM   #12
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1976 27' Overlander
Hackett , Arkansas
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Black Tank Repair:

This is my plan for repairing the black tank. I have contacted a local sheet metal fabrication company, and they can construct a new tank out of stainless steel with the holes in the same place as the original. However, I am going to reduce the size of the tank. The dimensions of the original are unique, so I am going to have the new one made 6.5" X 16" X 36" with a threaded piece for the toilet on top, a 2" pipe on top for the exhaust, and the 3" on the side for the dump valve (all matching the original for proper fitting). I will also have brackets welded on so I can attach the tank directly to the frame. I should never have to worry about it breaking or rusting, and it will be less expensive than buying a plastic replica of the original. The plastic replica, after shipping and handling, will end up costing a minimum of $600.00. I don't think that the custom stainless steel tank made locally will come close to that cost.

Rust Repair:

I realize that it would be better to remove all of the old metal and replace with new, but my money, tools, and capabilities are limited for this project right now.

Galvanized Belly Pan-
The rust was not as extensive as I thought (especially after seeing some of the projects posted in this forum). The galvanized belly pan was corroded along the T where it bolts under the tanks; the area where it bolts to the frame is fine. I have removed and sanded the corroded area, applied a rust converter-primer, and painted it. I will bolt on a new strip of 3" galvanized metal along the T where the pan bolts under the tanks. I'll replace the old bolts with new stainless steel bolts.

The metal bracket through which the two pipes run to the outlet (the valves are on the interior side- the 3" pipe on the exterior side) is rusted through on the bottom. I am going to use an angle grinder to remove the bottom 5-6" inches of the metal bracket. That will remove the majority of the corrosion. I'll bolt a couple of metal straps into the good metal to aid in securing the pipes.

I will also bolt a new piece of metal along the middle support bracket (between the two tanks) to which the belly pan is bolted along the middle. I'll use new self-tapping bolts to secure the pan to this middle section once I have it in place again. The pan will then be bolted to the frame on three sides and along the middle. However, since I will be cutting out the lower bracket right behind the bumper compartment, it will not be bolted at that location. However, the tanks will be strapped in, and the only weight on the pan will be the dampeners and the styrofoam insulation. It should be secure.

I'll just add more fiberglass and foam insulation under the floor to compensate for the smaller tank size.

Once the new dump valves are in place and no leaks are present, then I will apply a sealer (vulkem?) and reassemble the back bumper and the bathroom.

This is a rough sketch of my anticipated plan for restoring my bathroom facilities. If you have any suggestions or see any real problems with it, then please let me know. I'll take before photos this weekend, and post them next week.

Thanks,

Dennis
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Old 06-15-2007, 12:07 PM   #13
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Sounds like a good plan. I would be hesitent to remove any of the steel that is part of the actual frame. I'm having a little problem visualizing some the steel parts your referring to.

Jim
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Old 07-16-2007, 10:25 AM   #14
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1966 20' Globetrotter
Central , Illinois
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I am in the process of replacing the black water tank on our rear bath 1974 Ambassador. One of my challenges is the connection of the support frames for the tanks to the transverse c channel at the back is gone, completely rusted away. Apparently between the leak in the blackwater tank and the water coming in through the piano hinge for the rear storage compartment lid, rust and degradation was a long term problem.

The PO had "fixed" the problem by installing four angles that spanned the main frame and were outside the belly pan. This provided support for both holding tanks. Being brand new to trailers, I did not recognize the implilcations of the angles when we first saw our AS.

If anyone has a picture of this connection, could you please post it? It appears both frames bolted to an angle that came down between the grey and black water tanks. On our model, the grey and black water tanks are side by side.

How are you doing with finding a replacement tank or having a stainless steel one fabricated? I am about to start that process.

One other oddity I have run across is on the sheet metal pan that surrounds the tank - at the front end there is a 2" hole with a round, corrugated tube connected by four tabs. I had to bend the tabs in to get the pan to drop. Does anyone know where this tube goes and what it is for? Thanks very much.
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