Palomino HS 750 Grey tank is four gallons not 8 gallons as the manual said???

[Shrink52]

Our grey tank is supposed to be 8 gallons, but fills really fast. So we empty it until the panel had one dot, empty. Then used a gallon milk jug to fill it. We could only get four gallons in the tank before it backed up into the shower pan. What the heck? Is it possible that a 4 gallon grey water tank was installed by mistake. 4 gallon grey water capacity is fairly useless.

[GalsofEscape]

i would not depend on the lights to say it was totally empty. you may want to put the camper at a little tilt to the drain side and open the valve and drain it until no more water is coming out and then measure.
but no matter what, even an 8 gallon tank is terribly small would be useless to me.. my highwall popup had small waste tanks (around 10-12 gals IIRC) and i still used a waste tote (a 25 gal blue tote). That tote would last me a weekend and it made it easy to just haul it to the dump station instead of the camper. And i did not have to do any water usage management. Week long trips i would have to empty that tote every couple of days. it is big and bulky, but i felt necessary - it stored nicely on the floor of the pup --

Still use that tote with my current hybrid whenever we are camping without sewer hookup for more than 3 days and i have a 30 gal grey tank.