Has anyone measured actual capacity of 23/21/18 tanks?

[SYC2Vette]

When we dry camp, we usually try to shift as much to the black tank as possible since the grey is the one that fills first. The odd thing is that we will have 25-30% of our "23 gallon" fresh water still available when the "21 gallon" grey tank is full to the point of seeing the water level in the shower drain (and reads 100%). At that point the black is about 50% full or approximately 9 gallons which seems about right.

So either our 21 gallon grey has less than specified capacity, or our 23 gallon fresh holds more than specified capacity.

Not relevant to the question, but we usually can go 4 days and nights without much difficulty.

[field & stream]

Will follow this with interest, and hope others can supply data.

I measured the dimensions of our “23” gallon freshwater tank and it is approximately 24x20x10.5” so that is right on the 23 gallons specified.

Is it possible that your grey tank is not fully emptying for some reason?

[SYC2Vette]

Originally Posted by field & stream

Will follow this with interest, and hope others can supply data.

I measured the dimensions of our “23” gallon freshwater tank and it is approximately 24x20x10.5” so that is right on the 23 gallons specified.

Is it possible that your grey tank is not fully emptying for some reason?

I will have to see if I can measure the dimensions also. Regarding not fully emptying that is possible. One observation is that the black tank will read zero for quite a while before it starts any reading. Never gone over 75% on the black tank, mainly because I don't want to see what happens at 100% black. The grey tank on the other hand will start reading immediately going for example to 10-15% with the first shower.

[ROBERT CROSS]

POI....in my experience zero remains zero, until the first third has been reached.

Our tank has three sensors, 1/3, 2/3 and full. It remains on 'empty' 'til approximately 10gal are in it.
Same when it resisters full, just not so extreme, when the red full light comes on we have about 7gal wiggle room. 🥴

Bob
🇺🇸

[PatLee]

I find that the better job I do at leveling side to side, the better my sensors work.

[Dennis C]

Level tanks definitely provide a better reading. In my 2020 International, the SeeLevel II tank monitor seems to read in 6% increments. As a result, my black tank will show 0% until it hits 6%.

I haven't actually measured the tank volumes, but the grey tank sure fills up quickly. My grey tank has a published capacity of 30 gallons. We can easily make that work for 4 or 5 days with judicious water usage. I've found that a quick shower fills the grey tank by 11 - 15%.

[uncle_bob]

Hi

All of the tanks are *very* sensitive to side to side and front to back leveling of the trailer. That's not a big surprise given that they are big flat structures. This counts both for emptying and filling them. It is not at all uncommon to see the magic indicators change by 20% when the leveling is changed.

All of the tanks include both the tank it's self *and* the plumbing leading up to (and out of) the tank. In some cases this adds a couple of gallons to the total. Again, the pipes involved are mainly horizontal runs so leveling very much gets into the "how much".

If you are using a dump station to empty tanks, tossing blocks under the "far side" tires may help get the tanks fully empty. The drawback to doing this at the typical dump station should be obvious ... yuck ...

Bob

[NeahBay]

When we received our 2021 Caravel 16RB and before we used anything, I used a 5 gallon bucket to fill our 28 gallon combo black/gray tank and monitored what the meter on the galley wall showed. I put in 28 gallons of water and the meter showed 100%. I then continued to fill slowly with an additional 3 gallons until water appeared at the flapper of the toilet. No water at the shower drain (which I expected to see). Our meter and black/gray tank are accurate.

On the other hand, our 23 gallon fresh water tank only holds 21 gallons. I confirmed this by filling it full to overflowing, then drained into 5 gallon buckets. After a complete draining, lowing the tongue to get as much out as possible, I refilled with a flow meter and got the same result (20.9). AS owes me a larger FW tank.

Finally, we have stretched these capacities while dry camping to 10 days, we are currently on day 6, and tanks are: Black 63%, FW 40%… and FYI, 2 battleborn batteries at 12.8v, spotting sun through trees (180w on roof, portables almost useless), 1 day of clouds and rain. Going home today and getting some sun on panels too. We make it work for us, very comfortably.