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Old 09-16-2014, 05:32 AM   #1
HarryT's Avatar
Brand: Thor Motor Coach
Model: Four Winds Siesta 24SA
State: South Carolina
Posts: 40
THOR #762
Another question about my 08 Siesta 24 SA

I cleaned out my holding tanks today after our trip. The gauge does not work on the black tank so I filled it until water came up in the toilet then pulled the dump valve and drained it. All well so far. I then started filling the gray tank. The first two lights came on so I kept filling to get a good flush. It took forever and the full light never came on. I was listening for any wierd noises. I heard bubbling in the toilet so I immediately shut off the water and sure enough water was coming up into the toilet. On my old coach each tank had a vent coming out of the roof. I assume as this coach only has one vent on the roof they must have a tie in somewhere in the vent system. I will work on the warning lights on the tanks as this could be disasterous while flushing the gray tank if not being real careful.
Does anyone know if I am correct in assuming the vents from both tanks are linked together?

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Old 09-16-2014, 04:13 PM   #2
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FW28z's Avatar
Brand: Thor Motor Coach
Model: 2011 Four Winds 28Z
State: Michigan
Posts: 1,273
THOR #531
Sometimes one of the grey water drains may be plumbed into the black water tank. That is the way it is on my coach. The shower and kitchen sink are plumbed into the grey water tank, and the toilet and bathroom sink are plumbed into the black water tank.

It all has to do with accessibility I think, and since the bathroom sink gets used the least, then it does not add a lot to the black water tank capacity.

There should be a vent for each tank. There is on mine, but I don't have any idea about yours. Of course, the easy way to check is to look and see how many vents you have on the roof.
The only thing that works on a RV is the owner...
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