Black tank fills when connected to city water

[Retired irishman]

Strange issue here. When connected to city water my black tank slowly fills and will overflow toilet. I replaced entire toilet to eliminate all water and ball values
Is there another valve somewhere? I can't locate on schematics. This is a thor fe28 2019

[16ACE27]

Is the black tank filling? Or the toilet filling? An overfull black tank will not overflow the toilet unless you open the ball valve = it will come out of the vent above or the bathroom sink.

There are two sources of "city water" to the black tank:

The toilet fill/flush, and
The bathroom sink.

[dkoldman]

Originally Posted by Retired irishman

Strange issue here. When connected to city water my black tank slowly fills and will overflow toilet. I replaced entire toilet to eliminate all water and ball values
Is there another valve somewhere? I can't locate on schematics. This is a thor fe28 2019

Does it slowly fill when fresh water tank is filled, water pump on and nothing connected to City Connection?


I hate to ask this so don't take it as a negative but just a question. Any chance you have the water hose connected to the Sani Flush input versus City Water Fill? They could look a like. Picture of your hook up would help for those that don't have your coach

[16ACE27]

Originally Posted by dkoldman

Does it slowly fill when fresh water tank is filled, water pump on and nothing connected to City Connection?


I hate to ask this so don't take it as a negative but just a question. Any chance you have the water hose connected to the Sani Flush input versus City Water Fill? They could look a like. Picture of your hook up would help for those that don't have your coach

Winner, Winner! Chicken Dinner. Good catch, most likely the issue.

[Jimbo56]

Log into Thor Motor Coach site. Enter vin. You’ll find all your build specs. Did you discover the problem?

[fourthgear]

Not sure what toilet type you have ,but I had a flush Solenoid valve leak through & filled my Toilet Bowl & it was not part of the Toilet , it was in the water feed line to the toilet . I disassembled & cleaned & its been working fine since . Seems there was a lot of fine debris under the Valve & Valve seat .It was a slow leak by , but it filled the Bowl over night .