Best Portable Black Water Tank?

On our 5th wheel our tanks are 45 gallons each, we can last 18 -21 day on the black tank and 7 -10 days on the gray tank. We move every 14 days so don't have a problem with the black tank. When the gray tank gets full I dump some of it into 5 gallon buckets and hull them to the dump station.

If you have to empty the black tank every 2 days, either it is a VERY small tank or you should get your digestive tract issues/ibs looked at!
Gray tank(s) is a different story and totally dependent on how much water you do or don't use.

Sorry, don't have a recommendation on the best portable tank. Never needed one for black water and wouldn't go through the effort of hauling "irrigation" (gray) water to the dump.

When sizing your selection remember water weighs 8.25 pounds per gallon. A twenty-five gallon tote is going to be 210 pounds easy. Lifting that weight or just wheeling it around in soft dirt will be problematic.

The best solution is to use the volume more efficiently.

On a full hookup site, you want to use lots of water but off sewer, you can get away with using significantly less, so long as you don't empty the tank until it's mostly full. That will allow the solids to float out with the water.

How many of there are you that you think the black tank will fill every 2 days? With 2 of us using lots of water (on sewer sites), we get 4-5 days on the black tank. If we are careful, we can get a week without a lot of effort.

Another thought is if you are up and about, use the bath house rather than going back to your camper. Reserve the onboard system for nighttime or emergency (I have to go NOW!!!) type use.

I've borrowed them on occasion and the issue is a full tank is heavy and awkward. A 25gal blueboy will weigh upwards of 200lb when full. If your black tank is more than 25gal, you have the fun job of timing it so you shut the valve before it overfills and then clearing out the sewer hose.

After much research I ended up with a Barker tote with the big wheels. It's only been used a few times as it's not often that we stay without hookups longer than a long weekend, but for those few occasions it's been really nice not to have to unhook, drag the trailer to the dump, drag it back and hook everything back up. It probably didn't save any time since 2 trips with the tote isn't fast, but it was less stress.

As far as dealing it to the dump station, I got the Barker big wheel so that I could tow it at campground speeds off the ball, never actually used that as the sites we do extended stays at tend to be small beachfront sites where it's less than 1/4 mile to the dump.