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Old 12-16-2019, 01:32 PM   #81
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Join Date: Jun 2017
Location: 8000' in CO
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Quote:
Originally Posted by jdebevec View Post
Yes it's a 2018 35DB.
The gray tank only leaks when it's getting close to full, when parked. And it comes from somewhere around the top of the tank, drips down into the utility compartment. But just a drip, not a flood, so I don't think the pipe is completely separated.
One other odd thing it does: when draining the gray tank most of the water gushed down when you pull the valve, then it slows down for several seconds before all of a sudden the rest of the gray water empties all at once. Like the vent is restricted. But if there is no vent in the gray tank other than the single drain inlet, it certainly would be creating a vacuum as you dump the tank.
The pipe-to-tank engagement is just a slip fit in a rubber grommet. The grommet does have a lip at the bottom of it that the 1.5” pipe is supposed to bottom out against. So, in a perfect world, it should seal pretty darn tight. However, it seems to me like achieving perfection in this case would be very difficult. The pipe would have to be the EXACT correct length to bottom out against the grommets lip. The pipe would have to be cut EXACTLY square to hit the entire lip on the grommet. The grommet would have to be installed in the tank perfectly for it to square to the pipe. The tank would have to be perfectly perpendicular to the pipe. Then you introduce the fact that the shape of the tank could possibly change from when it is empty to when it is full (bowing of the top surface, etc). What I am getting at is, in theory, there are a million variables that can make that slip fit between the pipe and the tank not 100% water tight. At one point in time, it was suggested that the connection between the rubber grommet and the pipe was glued and that would probably help a lot (again, in theory). However, if you’ve read the entire thread, then you know that it was greased, not glued.

As for the draining of the grey tank, we experience the exact same condition you described when draining both the grey and black tank. As a result, I NEVER pull the drain handle all the way out. I most certainly believe it’s drawing a vacuum in the tank and I try to avoid that. Technically, since the pipe entering the grey tank doesn’t have standing water in it, then the vent stack being attached to the pipe and not directly to the tank should be adequate. That SHOULD be especially true in the case of the grey tank because the drain outlet is 1.5”, the inlet is 1.5” and the vent is 1.5”, so there shouldn’t be an issue with that. I THINK that part of the problem is the rain cap/vent thingies that are installed at the very top of the vent stack up on the roof. They have this waffle pattern to them and visually, it appears that they could easily hinder airflow while draining a giant tank full of liquid. I’d REALLY like to cut them off and try draining the tank with nothing on the top of the vent stack or trying a more traditional rain “cap” over the pipe. I just haven’t gotten the courage to cut them off yet because there isn’t a lot of pipe sticking up through the roof, so if something goes wrong, I’d be in trouble trying to repair it.

The other condition that can cause the stoppage you’ve described when draining the tanks is not enough slope if your sewer hose. I’ve noticed that if I don’t get a decent slope in the “stinky slinky” and especially, if there is a low point in it somewhere, that’ll back things up pretty quickly.
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Old 12-17-2019, 05:55 PM   #82
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Really helpful thread. thx
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