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Old 07-04-2007, 10:35 AM   #1
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Mid-bath termination valve fix

Perhaps this should be titled "Going after the valves from the bottom." The first step in working underneath (which I didn't do when I was working on the belly pan of the Caravel) is get some additional height. When you're thinking of hiking up some 6,000 lbs, my motto is "definitely over-engineer." I had an old solid core door and scraps of 3/4" plywood filling up my shop, so it was an easy decision. Here's the inside of what became two 10" high ramps and the ramps themselves (the ramp is about 30 degrees):

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When I thought more about it and the stress of being on uneven dirt, I decided they also needed a 2x8 under them. As it turned out, they needed to be solidly attached to the 2x8s or they slid backwards (an added benefit of the piece of 2x8 sticking forward was that it trapped the ramp as the first wheel rolled up on it, preventing any sliding). The additional height almost got in the way of the drain outlet, but by putting a scrap of 2x lumber forward of the contraption, I managed to get enough clearance.

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I admit to being surprised by how high the forward wheel was off the ground, here:

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As it turned out, I didn't need as long a ramp (48") as I thought. I think it could be substantially shorted and still do the trick. I think you only need to get one tire up on the horizontal surface. Maybe 30", or even as short as 24". Shorter would be better--you might even be able to pick it up.

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As you can see, clearance was excellent, I could almost sit up underneath. Actually, I wish it was about 5" lower, since I couldn't quite reach up to all the fittings when lying on my back. I think a ramp height of 7-8" would be sufficient if all you were going to do was work on the rear end. If you're doing the whole belly pan, I think the ramps should be as high as possible, considering the clearance of the drain, which is about 11" (give or take, depending on the shape of your axles).

Zep
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Old 07-04-2007, 10:49 AM   #2
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Quote:
Originally Posted by Zeppelinium
... I admit to being surprised by how high the forward wheel was off the ground ...
Yeah, and it doesn't take much, does it? I noticed a 3 - 4 inch-high curb is enough to get one of my wheels off the ground, and the axles are less than a year old.

Great job documenting your ramps and thought process.

Tom
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Old 07-04-2007, 10:50 AM   #3
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Oh, and congrats on double-Rivet Master attainment.

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Old 07-04-2007, 10:55 AM   #4
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I think the ramp would be the perfect height for me as my cross section height is most likely 5 to 6 inches higher then yours when I'm on my back.
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Old 07-04-2007, 11:11 AM   #5
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the valves

The following photo is the valve bay with all the parts installed. You can see the clamp for the external drain fitting is already loose and slid back along the 3" drain line:

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Note the big red arrow! You can see I cut the belly pan further inboard than necessary. I thought it was a cross member, but it turned out to be a galvanized enclosure for the black tank. The good side to this is that it protected the tank, but the bad side it that it's the full height of the space, so there is no space between the belly skin and the bottom of the enclosure, making it impossible to rivet the skin back together (no clearance on the inside for the rivet foot). Repairing, replacing, or attaching a cover in this area is not simple. Your best bet would be to leave at least 1" of belly skin outboard (to the street side) of the edge of the enclosure, so that you have an edge you can screw or rivet a cover plate to. The edge of the enclosure is not parallel to the frame (the frame is roughly parallel to the edge of the skin in the upper part of the photo).

A close look at the black valve reveals it can be removed by simply removing four large screws. The gray valve is not so simple. You have to disassemble the valve body by removing 9 screws into a space the is too narrow to accept even a Craftsman shortie screwdriver. You need one of those little "T-shaped" scredriver devices which include a ratchet (photo on request--I bought mine from Sears about 35 years ago and have only used it twice, but it's worth it's weight in gold when you need it).

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So, four steps and the assembly can be removed:
1. disconnect the black valve
2. disassemble the gray valve
3. undo the shafts to the handles
4. undo the clamp on the drain line

When you pull out the gray valve you destroy the gasket. Can't be helped, it's such a tight fit. A new gasket comes in the repair kit (my valves were the all-pastic type, repair kt number is Thetford 09872, about $19 each).

Note: all connections eventually lead to a clamp, so everything can be removed and repaired/replaced. The plastic body that the black valve screws into is clamped to the black tank. The main drain has a clamp where the pipe goes through the frame, and the gray tank is clamped about 4" forward of the valve on the other side of a reducing fitting. The actual gray drain is about 1-1/2" diameter, but I didn't measure it. One other thing to note. After I took the valve assemble out, I finally saw the gray clamp and decided I'd need that to be loosed to get the valve back in. That fitting is so tight, that even after loosening the clamp, I could barely move the half of the valve body still attached. This is one mother of a tight fit.

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Next: PUTTING IT ALL BACK

thanks for the notice TOM W! The top post in this thread was #1000 for me. Nice to be able to add something productive at such an auspicious time.

Zep
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Old 07-04-2007, 11:20 AM   #6
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Quote:
Originally Posted by Zeppelinium
... Note the big red arrow! ... I thought it was a cross member, but it turned out to be a galvanized enclosure for the black tank. ... the bad side it that it's the full height of the space, so there is no space between the belly skin and the bottom of the enclosure, making it impossible to rivet the skin back together
The black tank is supported/protected by an inch or two of styrofoam on its bottom & sides. It is possible to safely drill a rivet hole in the galvanized metal.

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Old 07-04-2007, 11:29 AM   #7
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Now, it just happens that the ole' junk box had two repair kits in it. One, the aforementioned 09872, and one with the stainless steel cover. The gray tank had to remain all plastic, since the replaceable cover is the piece that I left installed. The black valve, on the other hand, was totally removed and available. I got to thinking about the tight fit of the assembly and the relative thinness of the steel cover and decided that converting that valve would actually help me get the assembly back in, by providing about 1/8" wiggle room.

While the valves were open, I took the time to use some very fine sand paper to remove many ridges and scratches in valve bodies and sliding plate. I have no clue how abrasives get into the black tank, but it was more badly scarred than the the gray valve--did the PO have a gizzard? Totally clueless. The one thing I take away from this is, be careful what you allow to go down the sink--you can ruin the seal by damaging the plastic slider plate.

Voila! I was right about the clearance. Everything went back in place quickly, EXCEPT for the gasket for the gray valve. How to do this, with only the skimpiest of space? Without going into the details and the excercise of a consderable bit of seldom-used vocabulary, I eventually hit on looping the gasket around the forward piece of the valve, then gingerly feeding it in from all sides, using small nails through the screw holes to pin it in place as each section of gasket found it's place. I also used a little vaseline jelly to provide some viscous holding friction, which helped a lot. (yes, I'm pretty happy about this!)

Many of you will recognize that the valve handles are adjustable. When I reconnected them, I discovered that there was no way the gray valve could have been fully closed. I wonder how long this problem had existed? I think for some time, since the main problem with the valve was that it was clogged with accumulated trash that resembled a dried out corn cob, just not as hard. I think the PO allowed the adjustment to creep and didn't realize how simple the problem was. This allowed the slightly open valve to accumulated garbage, which totally prevented its closing. On the other hand, the valves needed to be repaired. The main seals were both badly cracked, even though the black valve continued to function perfectly.

Now I just need to figure out how I'm going to repair the skin...

Next thread: STRUCTURAL REPAIR OF THE UPPER ZIP DEE FITTINGS (part of the on-going removal of the vista view windows)

Zep
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Old 07-04-2007, 11:37 AM   #8
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Quote:
Originally Posted by TomW
The black tank is supported/protected by an inch or two of styrofoam on its bottom & sides. It is possible to safely drill a rivet hole in the galvanized metal.

Tom
You're absolutely right. I noticed the styrofoam, but it didn't occur to me. You can see the foam in the photo above of the black valve. But it's not 1" thick. I'll have to go measure it, but I think it's only 3/4" on the bottom.

OK, ran outside and measured. The sides are 1". The bottom is two 1/2" pieces, with a 1/16" sheet of plastic between them. I agree it would be safe to have a pop rivet foot sticking up in the lower 1/2" of foam. Cool (part of my aforementioned wide vocabulary).

Zep
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Old 07-05-2007, 10:34 AM   #9
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By the way, this is where this thread actually started.

http://www.airforums.com/forums/f444...lve-33046.html
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Old 07-07-2007, 10:43 AM   #10
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There are a couple of things I think should be mentioned that are not discussed above:

1. The 1/8" gap created by converting the black valve to stainless steel is too wide to simply be pulled closed by the 9 cover screws on the gray valve. You need to use a "come-along," like the longest Sears screw driver (what else is that one ever used for?). Some slight wiggling of the cover body while applying some force with the come-along will move it sufficiently.

2. Putting in the gasket might be done more easily if the gasket is put in place on the main valve body and the small nails inserted in the same direction as the screws would be eventually. If the nail heads are smaller than the screw threads, but larger than the pre-punched holes in the gasket, they would remain in place until the two halves are mated, but you could then push them out through the screw holes in the cover.

3. Converting to the stainless steel cover has the down side that the seal is part of the cover plate, so any future repair means a new cover plate--slightly more expensive. On the other hand, does anyone outlast a new seal? Although the Sovereign sat idle for 25 years, it was much used the first 5 years or so and even a completely dry 25 years didn't prevent the black valve from functioning.

Zep
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Old 08-31-2009, 06:51 PM   #11
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Question

Hello Zep,

Our black tank valve has been leaking the grey tank valve seemed OK

I thought I would replace both valves - I ordered and rec'd 2 new complete valves from Inland RV last winter.

I've got ramps built to raise the A/S up - similar to the ones you built.

Our A/S is a 1974 31' Sovereign Mid Bath.

Can you advise how to get these 2 new valves installed, or direct me in the right direction to get instructions.

I do not have a service manual.

Thanks,

Bob
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Old 08-31-2009, 07:13 PM   #12
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I did it by inspection. Don't be discouraged, the service manual isn't a help. It tells you the steps, but leaves out info on the joints. When you first look at the two valves, you will swear that one of them is cemented to the tank and you can't remove it. As I recall, you can remove both valves.

However, look at the replacement parts. You will see that the new seal is only on one side. If you dissassemble the valves (one of them, I recall) and leave the other half connected to the tank, you can fix it because the half that comes out is the half that needs replacing.

When you do this, you can get the entire other valve out. Just be warned that the operation takes some corner screw drivers, like the Craftsman ratchet screwdriver (there are others) that takes only about 5/8" clearance to get to a screw head.

Zep
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Old 01-25-2013, 08:53 AM   #13
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Nice thread Zep. So how would you handle something like this? I was wondering if it would be possible to leave the valve bodies on the Y-pipe and break the valve bodies apart where they split and remove the y-pipe. I have never had one of these valves apart so it is hard for me to envision if you can take these things apart that way and get them back together. I can't see a way to pull anything apart any other way accept moving the tanks apart.

Perry

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Old 01-25-2013, 09:14 AM   #14
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Quote:
Originally Posted by perryg114 View Post
.... I was wondering if it would be possible to leave the valve bodies on the Y-pipe and break the valve bodies apart where they split and remove the y-pipe. ...
Perry,





The valve bodies consist of two flat plates held together by 9 screws. From the look of your drawing, if you take out the screws on both valves, it seems that the "Y" fitting and the two halves of the valves that are attached to it should slip out. The problems I can imagine are:
  1. The "Y" fitting feeds a pipe that goes through a hole in the frame and so it can't slip out sideways. Do you have an access panel that allows it to go downwards?
  2. You can't get your hands into the space to use a screwdriver on some of the valve screws.
  3. The half of the valve attached to the tank is attached permanently (that's how it is in two of my Airstreams). If that half has the seal/gasket material, then you won't be able to fix the valve unless the seal is replaceable. Some models of the Thetford valve have a replaceable seal, some don't. I think it's the stainless version that has the permanent seal.
If you have an RV dealer near you, call and see if they stock the Thetford parts. If so, go there an look at them before you decide what to do. ... let me go look in the shop...

Aha, I have an example. This model (8706) is attached to the tank with 4 large stainless screws and is sealed by an O-ring. The valve gasket/seal is removable. Sometimes you can find this seal and the large body seal for the valve (like a head gasket, all the way around where the screws are) as an individual item.

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I just looked at my photos up in post #5 and I realize I don't know which way your valves will face the tank(s). Now I'm thinking the permanent attachment is to the pipe, not the tank. That means, however, that the 9 screws in the face of the valve are facing the tank. Ouch, if that is the case you'll need a short screwdriver and narrow hand...

Zep
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