Thanks for the toilet idea Bob. I turned off the water opened the black water tank valve and step on the toilet lever. No luck. It is full too. Not into the toilet full but close. There are two separate vents for grey and black tanks. I looked into both with a flashlight then ran #9 wire down them. The wire stopped after a few feet but I don't think there is a blockage in both vents.
The 9 wire goes into the grey tank easily and there seems to be no blockage. I haven't tried reaming the black water side for obvious reasons. I may try that next but why would both tanks not drain. Sounds more like venting but there are two vent pipes that would have to get plugged at the same time. I don't know what my last guests may have done or put in the system. They were here for 3 nights.
Anymore ideas?
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