Water Tank size....is it a lie?

[RhumbleFish]

Fair enough. But given that the outlet for the fresh water tank is never the lowest point in that tank, the differences are sort of academic. If you put 54 gallons into your 54 gallon tank and then measure how much water you can get out of the faucet via the pump, you aren't going to be anywhere near 54 gallons.

I feel you and the point you're making.

Reality is that - some tanks, yes - you pretty much can:

This tank is upside down. You can see the pickup in that artificial low spot, and the fresh water dump (very bottom). That looks like a pint or two of 'unusable' liquid.

And in some other tanks, no, you clearly cannot:

Where there's a lot sloshing around in the 'bottom,' across the entire lower area of the tank - maybe up to a gallon in these 10gal tanks.

So, maybe that's another point for reporting FW tank capacity, rather than actual usable water? I mean, I want a target to hit when I'm filling up before establishing camp at a non-water site.... but that's just a target, I'm still going to completely charge the plumbing system and fill my hot water heater while I've got the water source there... so it doesn't matter if it's 54 gal or 60 gal or 62 gallons.. I'll just go till everything is full, I've got ~62 gal showing on the ol flowmeter, and I've got water coming out of the overflow (and despite my DW saying "We've got enough!" cause she's always underestimating how much water we really use).

And regardless of low-spot-or-not, book shaped tanks are also present a (compounding) problem for the idiot lights... put that tank on any kind of slope, and the idiot lights won't be accurate. Cause they're not measuring amount in the tank, they're just reporting if the sensors are covered by liquid or not, and then representing a fill level. Not all that accurate.

Likewise, it's a bit of an issue in a hot water heater, where the anode/drain tube is close to the bottom, but - per your comment - not absolute bottom... so you can't get that last bit of water out of it (which is really dumb, right?). But it doesn't matter to operation, because you're always refreshing the contents of the HWH, to get hot fresh water... at which point it doesn't matter that you can't get the last quart of water out or not... untill you're going to empty it for the end of the season/storage. THEN it'd be nice to have an absolute bottom HWH tank drain.... building and accessing it, however, might be the challenge.

Good discussion, imho. Always stuff to consider, and - while it makes a steep learning curve even steeper - it's pretty great to always be learning. Still, s'a lot for the newbie to hold in their head, let alone for us graybeards.

Just my .02. I could be - and often am - wrong.

 

[ejl923]

Fair enough. But given that the outlet for the fresh water tank is never the lowest point in that tank, the differences are sort of academic. If you put 54 gallons into your 54 gallon tank and then measure how much water you can get out of the faucet via the pump, you aren't going to be anywhere near 54 gallons.

But nobody is reporting *usable* capacity.

Count my tank as having the outlet as the lowest point. In reality, I wish it didn’t as it gathers a lot of crud.

 

[TitanMike]

In many instances the fresh water may be defined by the water tank size, OR, may be water capacity which includes the contents of the water heater. And in many cases, depending on where and how the water overflow is located, the tank may not fill to published capacity.

There is a difference in "tank capacity" and "useable water". Where as, useable water is always less than tank capacity. One may have a tank capacity of 40 gallons but only 35 gallons as useable. It is called marketing.

Bob

In my case the FW tank is stated as 30 gallons. When I use all the water I can pump from the tank, then refill using meter, I put in 36 gallons. That's with all lines, filter, and water heater still full.

Can't complain.

 

[Boomerweps]

Funny, I just discovered this spec discrepancy today.
I got a flow meter and put 26 gallons into my FW tank when it started gushing out the overflow.
My TT listed FW spec is 32 gallons. 6 gallon water heater plus 26 makes 32. Looked up current model specs and they now list 26 gallons FW (not tank). Gray and black tanks still 23 gallons each.
Lack of FW tank vent hose is a problem for me, too. I tried to add one routed to the vent space on the fill assembly. I’d get about a half tank or so before water would gush out the fill. I figured either the hose was kinking somehow or water trapped in the overflow hose was preventing the venting. So I removed it.

 

[RhumbleFish]

Funny, I just discovered this spec discrepancy today.
I got a flow meter and put 26 gallons into my FW tank when it started gushing out the overflow.
My TT listed FW spec is 32 gallons. 6 gallon water heater plus 26 makes 32. Looked up current model specs and they now list 26 gallons FW (not tank). Gray and black tanks still 23 gallons each.
Lack of FW tank vent hose is a problem for me, too. I tried to add one routed to the vent space on the fill assembly. I’d get about a half tank or so before water would gush out the fill. I figured either the hose was kinking somehow or water trapped in the overflow hose was preventing the venting. So I removed it.

And now we can start to see discrepancies creep in:

From: https://www.jdpower.com/rvs/2019/cherokee-by-forest-river/m-16bhs/6586837/specs

• Fresh Water Capacity (gal / L) 32 / 121.1

From: 2025 Cherokee Wolf Pup 16BHSW Floorplan - Forest River RV (2025 unit, not quite the same floor plan, to be fair, probably shouldn't be included here)

• Fresh Water 26 gal.

From: 2019 Forest River Cherokee Wolf Pup 16BHS | RVshare

• Fresh water tank - 26.0 gal

From: 2019 Forest River Cherokee Wolf Pup West 16BHS specs and literature guide

• Total Fresh Water Tank Capacity. 38.0 gal. (which includes HWH)

SAME SITE:
From: 2019 Forest River Cherokee Wolf Pup 16BHS specs and literature guide

• Total Fresh Water Tank Capacity 32.0 gal.

All over the board, is what Im saying, with precious little rhyme or reason.

 

[5picker]

All over the board, is what Im saying, with precious little rhyme or reason.

R/V marketing hoopla... never trust it!

 

[kevinB24]

I tested my water meter in a 5 gallon bucket today and it was spot on. I then filled my tank ( which started completely empty along with the water lines) the meter read 35 gallons when it started coming out of the overflow hose. I then ran the water pump, filled the water heater, and water lines (until it was coming out of the sinks). Reset the water meter, and went to top off. It added only about 7 gallons of water. For a total of 42 gallons. That is a bit less than the 50 as advertised, and very disappointing. Then it seemed that the overflow hose ran forever, but the tank still reads full (not that I can trust the gauge).


Now I wonder if it is time to add a larger tank, so I can have more "Usable water" especially since I will be doing a lot of boondocking over the summer.

 

[RhumbleFish]

I tested my water meter in a 5 gallon bucket today and it was spot on. I then filled my tank ( which started completely empty along with the water lines) the meter read 35 gallons when it started coming out of the overflow hose. I then ran the water pump, filled the water heater, and water lines (until it was coming out of the sinks). Reset the water meter, and went to top off. It added only about 7 gallons of water. For a total of 42 gallons. That is a bit less than the 50 as advertised, and very disappointing.

Yep, that sort of tracks...especially the 6 gal for the heater, and the gallon or so for the plumbing. Question: in your first, post you mentioned you were able to put 39 gallons in before overflow. Confirming - Now, you could only put in 35 before overflow? (Just checking for a source of the discrepancy...). Also, where did you see the 50 gallons advertised?

FWIW, the manufacturer DID change the tankage on your 287bh for 2025 – increasing to what they are calling the "Niagara" 81 gallon fresh tank. Perhaps they found the tank in your model year too small.

Then it seemed that the overflow hose ran forever, but the tank still reads full (not that I can trust the gauge).

Yeah, careful here - a lower overflow hose (or, rather, an overflow hose that's end is lower than the tank height can start to function as a siphon, actively pulling water from the tank till the water can no longer be accessed by the overflow hose's entry point into the tank (saying that it may take some of the 'top' of that tank off, potentially losing you a few precious gallons). Do you have a tank vent in addition to an overflow hose?

Now I wonder if it is time to add a larger tank, so I can have more "Usable water" especially since I will be doing a lot of boondocking over the summer.

Replacing a tank can be a real project, especially if your trailer isn't set up to accommodate a larger tank. A lot of folks have found pony tanks, or even expandable bladders helpful to add to their fresh tankage. Likewise, it's not hard to bring a couple of 5 gallon gerry cans along, and get that water aboard, if needed.

Hope this helps.