Toilet Overflow

sundance_8 wrote:
What a mess. We use our travel trailer at our recreational property primarily for the fridge, restroom and microwave.
Well this past weekend we had our annual

family picnic with about 50 people.

Had the water system set for city water and hooked to my well pump. At the end of the day one of the kids runs out of the trailer and says the toilet is overflowing.
Long story short, evidently the city water inlet allows incoming water to run into the gray tank, when that filled then it filled the black tank and kept pumping water up thru the toilet when it was flushed.
Fortunately most of the water that dumped on the floor was fresh.
This trailer was bought used for this season so no history available.
Any suggestions on causes or fixes?

'Water inlet' does NOT feed any holding tanks.

Unless the foot pedal on the toilet is stuck in the open position and allowing water to enter your toilet all the time there is no way fresh water can get into your black tank.

Many RV's do have the bathroom sink dump into the black tank. So if "50" people are brushing teeth and/or washing hands all day THAT water also goes into the black tank making the black tank fill up even faster.

50 people using your RV and toilet and bathroom sink!? :E

I'd say you have a very very full black tank.