How much tank space is left?

dlb

How much tank space is left when the gray or black tank lights up as full?  

We have a 2021 Tab 400 Boondock

Binghi

We have a 2021 400. We can’t tell from the panel whether the gray or black tank is full because the lights are too unreliable. We know our gray tank is full when the kitchen sink stops draining. We determine whether the black tank is full by looking down the mouth of the toilet when flushing it. In our experience, the gray tank fills up faster than the black tank.

qhumberd

In our 2019 400 the gray tank sensors are not super accurate. When driveway camping last year the grey tank sensor was showing full and our portable tank drained the grey empty and was full and it held 15 gals. Grey tank is supposed to hold 18 gal full, at which point it likely will back up on shower floor first.

Black tank I would agree with @Binghi and just open the drain flap and look with a strong light.

fwunder

Black tank - Fahgettaboutit. Grey tank - mine seems pretty accurate so far. I just tested my capacity by filling with 5 gallon buckets. Took 3 + about a half before galley sink started backing up. Yes, galley sink stopped draining before any water in shower pan - must be check valve.

2023 400 BD

dlb

Thanks for these responses.  I appreciate those who measure and test, data is important.  We have done the look and see method for the black tank and have just emptied the grey tank when the lights hit full.  Only once have we flooded the shower, while showering,  the sink has not been the indicator for us.