We discovered a leak a few months ago, starting an adventure in troubleshooting. We first saw it after a massive thunderstorm in South Dakota over the summer. This was a major bummer as it suggested that it was coming from the outside in. Observing for a bit confirmed that the water only showed up after a significant rain. This ruled out an internal plumbing problem, thank goodness, but that just left the only option as the water coming in from the outside. In the image, you can see where the water was showing up (there is still a bit of water in the foam). Of course, it could be coming from anywhere and just showing up here, but it was most likely a from something in the rough proximity of where the water was pooling.
The first guess was that the water was coming in from the air vent in the back, so I built a little dam around the vent with butyl tape, flooding it for a few hours. This did not replicate the leak. After that, I repeated this testing on all of the possible places on the roof: the fan vent in front, the two antennas, and the solar junction box where the power comes into the van. This showed nothing.
Reading in the sprinter forums, I’ve seen that the shopping cart bumpers on the side can leak, so, I thought that I couldn’t do any harm by just putting a silicon bead on the top of that trim. In addition, the van exterior is not one solid sheet of metal, it’s three joined together. On the side of the van, the three pieces are joined with a black silicon seal, while on top, there’s a welded strip. Perhaps these are leaking?? I decided to just pour dicor on the back roof joint as it couldn’t hurt, and might seal it.
After the first good rain after this sealing, I haven’t seen the water appear again. We’ve had a couple of rains since then and I don’t see water pooling. The joys of van ownership. I’ve had two leaks: one from a defective water tank, and now, one that appears to be from poor sealing from Mercedes.
Takeaway: I’d suggest everyone put a silicon bead like the one pictured above on their van. I don’t see how it could hurt anything, and it looks like it is fixing a leak.
Speaking of Water
I’ve wanted more freshwater capacity & to fix my initial plumbing mistakes for some time. I finally got around to doing so by adding an additional 25 gallons. This doubles our capacity. I’m plumbing the two tanks together so that you can fill both at the same time, or have the option to just use one tank or the other.
The existing plumbing has two problems:
there is a single gravity fed entry into the pipe with no air vent. This makes filling the tank slow and prone to back-burping. It’s OK, but it would be much nicer to just plug a hose full blast.
there is no easy way to drain the tank. If you have been following along, you may remember that I forgot to take evasive action during a winter which froze and broke a pump.
Unfortunately, to get the volume that I need, a little tank platform is required, so I built a box for it to sit on. With the two tanks ganged together, I can fill the new tank and it will drain to the lower (if that valve is open). This fixes the old tank filling problem. The old ABS inlet now gets capped with some air holes drilled into the cap for a true vent.
One disadvantage of the way I’ve arranged everything is that the pump isn’t very accessible. I’m going to have to unscrew a few different things if the pump needs to come out.