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

[kevinB24]

I was filling my fresh water tank today on my 28bh artic wolf Fifth Wheel. I used a water meter on the hose to count the gallons. My tank is "Advertised" as a 49 gallon tank. While filling it water started coming out the water tank overflow hose. It seemed like a lot of water was flowing out of it. I have had that before and when I checked the tank only registered 2/3 when it stopped. This is not a problem, but I only had put 39 gallons in it. This is the first time I used the water meter, but I am not sure of the issue. I know I drained the water tank all the way at the end of last season. On my control panel it is registering as full.

Could the water meter be bad? Is there air in the tank/line, or is my tank size incorrect? Has anyone had this issue?

 

[ejl923]

On my 16bhs, The overflow/vent was just a fitting on the tank, no hose connected, about 2/3 the height of the tank so when I filled it poured out there. I connected a hose and vented correctly. I don’t know if this is cost cutting or a way to keep their flimsy tanks from being filled all the way.
Anyway, you might have the same problem. My tank is open to the bottom so easy to see.
Also, test the water meter on a 5 gallon bucket or two

 

[Willhound]

It's possible that depending on water flow there is air getting trapped in the tank, try filling at just above a dribble and see what happens. Also your overflow hose is likely mounted somewhere down on the side of the tank, how far from the top is hard to say unless you can see it. Even an inch will make a difference. Advertised tank sizes are the overall volume of the tank, not that it is possible to completely fill that space. Although 39 gal in a 49 gal tank does seem low. I still suspect the overflow location.

 

[KyDan]

I don't know what your fill port looks like but if it's the kind with a cap you remove and stick a hose
inside I suggest getting a hose "pig tail". IE one of the old rubber washing machine connection hoses.
Cut it in half. Now you have two pieces of hose - each with a female hose end. Screw on your city water hose and shove the pig tail into the fill port as far as you can. It should go in at least 18-24 inches. Now fill
the tank. Also I suspect the water meter. Finally if you can- drain the tank into 5 gallon buckets and get
an accurate measure of how much water was in there.
The 2nd piece of washer hose is a great watering can filler or wash bucket filler for use around the
campsite or at home.
Happy Trails!

 

[kevinB24]

On my 16bhs, The overflow/vent was just a fitting on the tank, no hose connected, about 2/3 the height of the tank so when I filled it poured out there. I connected a hose and vented correctly. I don’t know if this is cost cutting or a way to keep their flimsy tanks from being filled all the way.
Anyway, you might have the same problem. My tank is open to the bottom so easy to see.
Also, test the water meter on a 5 gallon bucket or two

I have a hose that comes out from the underbelly so I haven't dropped the underbelly to explore where it is attached. . I have a valve on the overflow hose, but can't close it while filling.

 

[ejl923]

I have a hose that comes out from the underbelly so I haven't dropped the underbelly to explore where it is attached. . I have a valve on the overflow hose, but can't close it while filling.

If it is the overflow hose, definitely don’t want to close it, you will pressurize the tank and could cause some serious problems. I ran my hose up to the height of the fill port where there was a spot for it. You may be only filling to height of overflow

 

[Aussieguy]

depending how level you are when you drained it there could be some gallons still in the tank

and .... did you calibrate the water measuring little meter?

today's obsession with ... is it exact is bound to drive people nuts
have I got 49 or 50 gallons
is my battery really 100ah

look at my avatar ... blue bucket is the gray tank
no such thing as a black or a indoor dunny
we still had fun camping and never batted an eye if we was missing a drop of two in the tiny little fresh water tank which fed a single hand pump on the sink

kinda miss those days...
you could always tell when your neighbor was up in the middle of the night getting a glass of water

 

[RhumbleFish]

Could the water meter be bad? Is there air in the tank/line, or is my tank size incorrect? Has anyone had this issue?

Sounds like you're on top of things, Kevin, in particular with not closing the overflow hose when filling. I regularly dump all of my tanks and travel completely dry, filling only when in-or-near camp, so a lot of time doing water management.

Tanks are weird. And filling tanks can be weird, too, for all kinds of surprising reasons (less surprising with some fluid dynamics, but surprising nonetheless).

I think listed tankage is generally pretty accurate, as the tanks (and water heaters) purchased by Rockwood have known/measured capacities that can be published. Rockwood specs and buys a 50 fresh gal tank? Rockwood puts 50gal on the freshwater capacity. Rockwood specs and buys a 6gal hot water heater? Rockwood puts 6gal on the water heater. Completely fill that empty tank AND fill the HWH? You've got near abouts 56gal aboard. I did the drain-and-measured-fill thing and got pretty close to listed tankage, especially for the known qty of the fresh tank (black tank is more of an estimate, though, based on the appearance of water near the bottom of the toilet side pipe, which extends INTO the black tank - so I don't think the listed measurement is wrong, just that my experiment wasn't accurate).

However, since the (below-floor/in-frame) tanks are predominantly flat and book-shaped, ANY off-axis FILLING or DRAINING won't have the desired effect (to fill or empty to completion), and this tilt can have a LOT of impact (and, in particular, on book-shaped tanks). We all know the idiot lights aren't accurate. When you see the sensor placement in the side of a tank, you'll see the reason why...

Here you can see the fill port (top/center) the vent port (top center, next to fill), the sensor array (to the left), the water draw point (bottom/center) and the dump (very bottom)

See the very top sensor? The one that - when it senses water - lights up the idiot light that reads "full?" This tank still has some more tank left above that. In my case, it's 12 gallons worth of difference btween the light coming on, and the tank being REALLY completely full (to the point of water coming out the vent port). And if you take a tank that reads full, with the light JUST coming on (and the water JUST up to the level of the sensor, but not all the way away from it), and then tilt the tank away from the sensors, the full light will go off.

The vent port should be at the same height as the fill port - and in this case, it is. There's is likely a little bit more room in that tank, but it seems to be a negligible amount. still, across the entire surface of the tank, that could add up to a decent amount of water.

Likewise, the external vent height GENERALLY should be at the same height as the fill entry point (note how this is different than the ports in the tank, this is actually where you interface with the tank - fill entry point on thd side of your coach or in your wet bay, and the vent hose or vent port). If the vent is any lower than the fill, then water put into the tank via the fill port will overflow out the vent before backing up the fill port. Nowadays, many RV fresh tank vents are co-located with the filler hose inlet... however, some aren't and if your overflow hose is at a lower height than the fill spout (or air vent), then you'll get water out of that before water comes out the filler inlet.

Tank dumps are impacted, too - but can mostly get around this by virtue of (1) a low spot can be manufactured into the tank with a drain attachment there - as shown the above - or (2) tank bulging, with a drain attachment in the low spot/center of the tank (though this placement creates a(n acceptable) weakspot in the tank floor). But if your Arctic Wolf was tilted away from the drain port to any degree when you dumped last year, your tank could have still had water in it.

And, as others have mentioned, if your vent hose OR filler hose gets a kink in either of them - of are blocked by any manner, it can cause problems with filling your tank, even to the point of pressurizing them, causing them to change dimension/swell like a ballon - an issue that can cause floors to pop up, or tanks to drop out.

Lastly, if your flowmeter is even remotely out of calibration, it will (most likely) underreport how much it's filling.

But you know all of this.

I'd be tempted to (1) super duper level your trailer, (2) dump everything, (3) calibrate your flowmeter by pumping a known/measured quantity of water (like pulling water out of a 5 gal bucket), and then trying again.

Sorry for the length, hope this helps. I could be - and often am - wrong.

 

[5picker]

Also take into consideration, manufactures have long added the water heater's tank capacity to the total of fresh water capacity.
In today's world with tankless water heaters, the published capacities may not have changed in the literature.

 

[kevinB24]

Also take into consideration, manufactures have long added the water heater's tank capacity to the total of fresh water capacity.
In today's world with tankless water heaters, the published capacities may not have changed in the literature.

Sounds like you're on top of things, Kevin, in particular with not closing the overflow hose when filling. I regularly dump all of my tanks and travel completely dry, filling only when in-or-near camp, so a lot of time doing water management.

Tanks are weird. And filling tanks can be weird, too, for all kinds of surprising reasons (less surprising with some fluid dynamics, but surprising nonetheless).

I think listed tankage is generally pretty accurate, as the tanks (and water heaters) purchased by Rockwood have known/measured capacities that can be published. Rockwood specs and buys a 50 fresh gal tank? Rockwood puts 50gal on the freshwater capacity. Rockwood specs and buys a 6gal hot water heater? Rockwood puts 6gal on the water heater. Completely fill that empty tank AND fill the HWH? You've got near abouts 56gal aboard. I did the drain-and-measured-fill thing and got pretty close to listed tankage, especially for the known qty of the fresh tank (black tank is more of an estimate, though, based on the appearance of water near the bottom of the toilet side pipe, which extends INTO the black tank - so I don't think the listed measurement is wrong, just that my experiment wasn't accurate).

However, since the (below-floor/in-frame) tanks are predominantly flat and book-shaped, ANY off-axis FILLING or DRAINING won't have the desired effect (to fill or empty to completion), and this tilt can have a LOT of impact (and, in particular, on book-shaped tanks). We all know the idiot lights aren't accurate. When you see the sensor placement in the side of a tank, you'll see the reason why...
View attachment 1107718
Here you can see the fill port (top/center) the vent port (top center, next to fill), the sensor array (to the left), the water draw point (bottom/center) and the dump (very bottom)

See the very top sensor? The one that - when it senses water - lights up the idiot light that reads "full?" This tank still has some more tank left above that. In my case, it's 12 gallons worth of difference btween the light coming on, and the tank being REALLY completely full (to the point of water coming out the vent port). And if you take a tank that reads full, with the light JUST coming on (and the water JUST up to the level of the sensor, but not all the way away from it), and then tilt the tank away from the sensors, the full light will go off.

The vent port should be at the same height as the fill port - and in this case, it is. There's is likely a little bit more room in that tank, but it seems to be a negligible amount. still, across the entire surface of the tank, that could add up to a decent amount of water.

Likewise, the external vent height GENERALLY should be at the same height as the fill entry point (note how this is different than the ports in the tank, this is actually where you interface with the tank - fill entry point on thd side of your coach or in your wet bay, and the vent hose or vent port). If the vent is any lower than the fill, then water put into the tank via the fill port will overflow out the vent before backing up the fill port. Nowadays, many RV fresh tank vents are co-located with the filler hose inlet... however, some aren't and if your overflow hose is at a lower height than the fill spout (or air vent), then you'll get water out of that before water comes out the filler inlet.

Tank dumps are impacted, too - but can mostly get around this by virtue of (1) a low spot can be manufactured into the tank with a drain attachment there - as shown the above - or (2) tank bulging, with a drain attachment in the low spot/center of the tank (though this placement creates a(n acceptable) weakspot in the tank floor). But if your Arctic Wolf was tilted away from the drain port to any degree when you dumped last year, your tank could have still had water in it.

And, as others have mentioned, if your vent hose OR filler hose gets a kink in either of them - of are blocked by any manner, it can cause problems with filling your tank, even to the point of pressurizing them, causing them to change dimension/swell like a ballon - an issue that can cause floors to pop up, or tanks to drop out.

Lastly, if your flowmeter is even remotely out of calibration, it will (most likely) underreport how much it's filling.

But you know all of this.

I'd be tempted to (1) super duper level your trailer, (2) dump everything, (3) calibrate your flowmeter by pumping a known/measured quantity of water (like pulling water out of a 5 gal bucket), and then trying again.

Sorry for the length, hope this helps. I could be - and often am - wrong.

Thanks for the update it is great information. I will have to check the capacity and water meter with a 5 gallon bucket when I dump it. I always empty it and the low points for the water lines after I level up as the tank has a valve at the bottom to empty it. I also never fill it or run the water pump with the drain valve closed. I am hoping it is just the meter, but eventually have to pull the underbelly to see what the deal is

 

[BD Nomad]

I was filling my fresh water tank today on my 28bh artic wolf Fifth Wheel. I used a water meter on the hose to count the gallons. My tank is "Advertised" as a 49 gallon tank. While filling it water started coming out the water tank overflow hose. It seemed like a lot of water was flowing out of it. I have had that before and when I checked the tank only registered 2/3 when it stopped. This is not a problem, but I only had put 39 gallons in it. This is the first time I used the water meter, but I am not sure of the issue. I know I drained the water tank all the way at the end of last season. On my control panel it is registering as full.

Could the water meter be bad? Is there air in the tank/line, or is my tank size incorrect? Has anyone had this issue?

Dealers routinely count the water heater capacity as part of the fresh water tank capacity. I know, as I had a similar issue where I was routinely 6 gallons short of the advertised capacity (As it turns out, my water heater tank is 6 gallons). I mentioned it in passing to a dealer, and that's when he enlightened me that they ad water heater capacity to fresh water total.

Hope this helps

 

[GolfingDave]

You mention overflow hose. I do not have one but I have a vent at the fill opening.
I use my ShowerMiser to fill and leave the fresh water fill opening cap off while doing it. Mainly for more venting while filling. Have never shoved a hose down it to fill.
Water will start exiting(usually in spurts) the vent when it gets to a certain point and then quit after a minute or so. It then continues to fill another ten gallons until it comes out the fill opening.

My bet is with the tank hose opening getting air trapped or water trapped also.

 

[bikendan]

Dealers routinely count the water heater capacity as part of the fresh water tank capacity. I know, as I had a similar issue where I was routinely 6 gallons short of the advertised capacity (As it turns out, my water heater tank is 6 gallons). I mentioned it in passing to a dealer, and that's when he enlightened me that they ad water heater capacity to fresh water total.

Hope this helps

RV Manufacturers also count the water heater capacity as part of the FW capacity.

 

[tomkatb]

Be advised that the fill line is larger than the overflow.

You run the risk of the tank falling apart if you forget and leave the filling line run. The tank will get round shaped and come apart. Deflagration I think.

Yes. In the past the water heater was included in the tank capacity.

Those leds in the control panel are borderline useless.

 

[KethCamps]

The overflow hose might be letting water out too early because of trapped air or how it's positioned. Fill it slowly and check if there's any leftover water from last season.

 

[RhumbleFish]

RV Manufacturers also count the water heater capacity as part of the FW capacity.

Dealers routinely count the water heater capacity as part of the fresh water tank capacity. I

Nor should we forget "informative" sites, like J.D.Power.com or RVUSA.com, let alone the myriad of ads that are aggregated on sales sites/channels.

But there's no definitive "Yes, they do!" or "No, they don't!" The real trick is that it's common practice to do it BOTH ways (likely by the listing agency), so people need to be watchful for it... because there's no defined standard, it's a policy (or lack thereof) that can surprise people, no matter which way it is.

For trailers with smaller freshwater tanks, the typical 6 gal hot water heater can contain a sizable part of a trailer's "fresh" water. OP's 287bh Arctic Wolf fifth wheel has a (seemingly undersized for that sized trailer) 49gal fresh tank, a 6 gal hot water heater represents ~12% of his fresh tankage. Apparently this was corrected in newer models, with tankage being increased significantly to 81 gal, and 6gal is now only a 7% impact. Does it matter? For a buyer moving from one RV to another with onboard water having been an issue previously, it sure could be. "We had a 30 gal tank and that wasn't quite enough." Right up there with "we had plenty of fresh water, but ran out of gray space fast and had to break camp, go dump, and then set-up all over again."

What's the takeaway? Buyers and operators alike just need to add this to the (already steep) learning curve.

Just my .02, hope this helps. I could be - and often am - wrong.

 

[Qwkynuf]

Nor should we forget "informative" sites, like J.D.Power.com or RVUSA.com, let alone the myriad of ads that are aggregated on sales sites/channels.

But there's no definitive "Yes, they do!" or "No, they don't!" The real trick is that it's common practice to do it BOTH ways (likely by the listing agency), so people need to be watchful for it... because there's no defined standard, it's a policy (or lack thereof) that can surprise people, no matter which way it is.

For trailers with smaller freshwater tanks, the typical 6 gal hot water heater can contain a sizable part of a trailer's "fresh" water. OP's 287bh Arctic Wolf fifth wheel has a (seemingly undersized for that sized trailer) 49gal fresh tank, a 6 gal hot water heater represents ~12% of his fresh tankage. Apparently this was corrected in newer models, with tankage being increased significantly to 81 gal, and 6gal is now only a 7% impact. Does it matter? For a buyer moving from one RV to another with onboard water having been an issue previously, it sure could be. "We had a 30 gal tank and that wasn't quite enough." Right up there with "we had plenty of fresh water, but ran out of gray space fast and had to break camp, go dump, and then set-up all over again."

What's the takeaway? Buyers and operators alike just need to add this to the (already steep) learning curve.

Just my .02, hope this helps. I could be - and often am - wrong.

But I have never seen a specification that says "freshwater TANK capacity". They say "freshwater capacity". Can anyone argue that any water that is contained in the plumbing - pipes/hot water tank/ice maker lines/etc should not be counted as fresh water?

Looking at it from the other direction - if you started with an empty system, filled the fresh water tank, then turned your pump on and primed all of the lines, and then topped off the tank - wouldn't you be very close to the capacity specification?

 

[RhumbleFish]

But I have never seen a specification that says "freshwater TANK capacity". They say "freshwater capacity". Can anyone argue that any water that is contained in the plumbing - pipes/hot water tank/ice maker lines/etc should not be counted as fresh water?

Looking at it from the other direction - if you started with an empty system, filled the fresh water tank, then turned your pump on and primed all of the lines, and then topped off the tank - wouldn't you be very close to the capacity specification?

Honestly, I dunno. It SEEMS like you're trying to backwards engineer a single/universal common approach to the issue – which is being reported as generally not the case (especially from a historical perspective).

I mean, I get it - it makes sense that freshwater capacity ought to accommodate all the freshwater in the entire system from a USAGE perspective. Likewise, it sorta makes sense that tankage is the important factor to report, because it's the easiest to do so (without having to accommodate individual differences in plumbing and or accessories). Eg, the same plumbing setup in a bigger trailer with longer plumbing runs AND an icemaker AND a larger HWH would have a larger ultimate capacity listed than in a smaller trailer, with shorter runs, and neither of those accessories... When, practically speaking, they have the same freshwater tankage. Sort like listing payload capacity on a vehicle, without accommodating how it's optioned. From a logistics standpoint, a manufacturer would have to calculate this for every individual trailer, as opposed to each trailer model, as opposed to - you know - just listing tank size.

Factual material tends to disseminate outward from manufacturing data. Likewise, there's anecdotal reports and changes in time. As an example that is familiar to me, I can say for certain that my 22 (Same as 25 spec) Rockwood Roo 235S has a 54gal freshwater tank (measured and validated) with 6 gal HWH (in addition) for a grand total of 60 total gallons of fresh water (plumbing lines being near negligible, with an absolute maximum of >2 gallons for the entire internal plumbing system, considering antifreeze use).

Every listed instance I can find searching for "rockwood roo 235s fresh water" turns up 54 gallons, and - in two instances (RVUSA and RVTrader) - they actually reference "fresh water tank" capacity. Maybe this is a result of newer data, and newer common practice among manufacturers, and maybe it's jsut conscientious owners/sellers, but you can bet that there's going to be a dealer somewhere who adds fresh tank and HWH capacity together for their own unique listings.

The fact that there's no common accepted standard for reporting capacity is an issue, is what I'm saying.

Of course, that's just my .02 (or .03, depending on how you measure). I could be - and often am - wrong.

 

[Qwkynuf]

Honestly, I dunno. It SEEMS like you're trying to backwards engineer a single/universal common approach to the issue – which is being reported as generally not the case (especially from a historical perspective).

I mean, I get it - it makes sense that freshwater capacity ought to accommodate all the freshwater in the entire system from a USAGE perspective. Likewise, it sorta makes sense that tankage is the important factor to report, because it's the easiest to do so (without having to accommodate individual differences in plumbing and or accessories). Eg, the same plumbing setup in a bigger trailer with longer plumbing runs AND an icemaker AND a larger HWH would have a larger ultimate capacity listed than in a smaller trailer, with shorter runs, and neither of those accessories... When, practically speaking, they have the same freshwater tankage. Sort like listing payload capacity on a vehicle, without accommodating how it's optioned. From a logistics standpoint, a manufacturer would have to calculate this for every individual trailer, as opposed to each trailer model, as opposed to - you know - just listing tank size.

Factual material tends to disseminate outward from manufacturing data. Likewise, there's anecdotal reports and changes in time. As an example that is familiar to me, I can say for certain that my 22 (Same as 25 spec) Rockwood Roo 235S has a 54gal freshwater tank (measured and validated) with 6 gal HWH (in addition) for a grand total of 60 total gallons of fresh water (plumbing lines being near negligible, with an absolute maximum of >2 gallons for the entire internal plumbing system, considering antifreeze use).

Every listed instance I can find searching for "rockwood roo 235s fresh water" turns up 54 gallons, and - in two instances (RVUSA and RVTrader) - they actually reference "fresh water tank" capacity. Maybe this is a result of newer data, and newer common practice among manufacturers, and maybe it's jsut conscientious owners/sellers, but you can bet that there's going to be a dealer somewhere who adds fresh tank and HWH capacity together for their own unique listings.

The fact that there's no common accepted standard for reporting capacity is an issue, is what I'm saying.

Of course, that's just my .02 (or .03, depending on how you measure). I could be - and often am - wrong.

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.

 

[Bob K4TAX]

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