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After purchasing the RV we drove from San Diego back home. Somewhere along the way on that trip the black water tank drain line fell off, well, half of it anyways. I knew I had to get down there and replace that line. Turns out that the open close valve on that tank also didn't seal 100%. It would drip. Next, the waste tank gauge always read well below 0. The gauge didn't work.
I had 3 things to do, all related to the waste tank. Better do them all in one shot rather than coming back to climb under the waste tank again and again.
I opted to replace the entire waste tank valve. The RV had a Thetford valve from the factory. I got a new Thetford valve. Getting the old valve out was painful. There is a frame cross member you have to remove. Once that was done I removed the old valve only to realize that the base is permanantly attached to the tank. That wouldn't be a problem except that the base has four screw hole, one of which was broken and 1 was stripped out. So it actually has 2 screw holes, which is not enough for a good seal.
I had to get creative. I opted to drill through the base to install bolts in two of the holes. One hole got a screw as intended. The last screw hole was broken and I couldn't drill through it to install a bolt because that would have protruded into the waste tank. I opted to install a block of wood to pressure fit that corner of the waste valve in place.
The sender provided a similar challenge. There were 5 screws but 3 were stripped out. I ended up installing the sender with a couple good screws and a ton of silicon. Hopefully it holds.
As for the waste pipe itself, I opted to use a bunch of 3" rubber couplings with lenghts of rigid 3" pipe. The result is that the pipe can tuck up hight against the RV floor, or it can fall down a foot or so to allow easier draining. This seems like it will be the perfect setup for draining without worying about any RV specific drain swivel joints or 90 degree bends. Time will tell.
Lastly, there is supposed to be a handle that when pulled, opens the waste tank valve. There was no handle on my RV. There was just a bolt head. You could pull and push on that bolt to operate the valve. It was not a very nice user experience. I ended up making my own handle out of thin steel, painting it, and installing it. The new handle makes it much easier and enjoyable to open or close the waste tank valve. I have no idea what the handle looked like from the factory. Believe it or not, there are not too many pictures of 1970's GMC motorhome waste tank handles on the internet.
After the entire install was complete, I can confirm there are no leaks. I don't know yet if that sender is working correctly. The guage it connects to still registers far below zero so I am pretty sure the gauge is bad. Pictures
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| | | | | | you can see the ground wire to the old sender was broken | | | | | | Interesting, the pipe just runs outside that o-ring. Any female 3 | | | | | you can see the spot the frame cross member support was | | | | | this base is permanently attached to the tank | | | | | one broken screw stud (upper left). Lower right is stripped out :( | | | | | | | | | old valve is Thetford model 2x SS E M Valve, part number 03632 | | | | | old sender removed, 3 out of 5 screw holes stripped | | | | | old sender was very stiff and didn't want to move | | | | | | | new valve, Thetford model 08707 | | | | | | | | | that wood block ultimately needed to move to another screw hole | | | | | | | | | old bolt you would pull on to open and close waste drain valve | | | | | | | | | | | | | | | installed with 2 good screws and bucket loads of silicon to seal it | | | | | | | you can see lower two holes were drilled through to allow for bolts to be installed | | | | | | | | clened up sender unit ground point | | | | | | | 