Black Tank Level Rises without Use?

[dasams]

We are parked in my brother's driveway under shore power, city water but no sewer hook-up. When we arrived, our black tank was at 75% so we've been using his facilities. After two days, the level has risen from 75% to 94%. Can anyone explain how this is happening?

We leave tomorrow and I'd like to avoid hitching up to dump the tank this afternoon. Also, how much reserve do we have above 100%?

We have a new 2017 FC 25.

TIA, Dave

[SteveSueMac]

Hi. A few guesses:

1) your monitor is not adjusted correctly. Have you looked down the hole? At 94% you should be able to see water pretty high up the pipe. There should be a shutoff on the feed to the toilet so when you open the flapper you're not demanding water.

2) if your water pump is on and you're connected to city water, you may have a leak (have you heard the pump kick in?)

3) your toilet bowl/flapper seal isn't tight

4) your bathroom sink may drain to the blank tank (apparently that happens in some models - not sure if yours is one of them).

Good luck!

[dasams]

Originally Posted by SteveSueMac

Hi. A few guesses:
4) your bathroom sink may drain to the blank tank

Thanks and bingo! I just read my owner's manual and some, but not all, models drain the lav sink into the black tank. This was good to learn so that I can better manage my tanks.

Thanks, Dave