How I increased the USABLE freshwater capacity on our 2019 T@B 320S

mnmarkiemark

Getting only 9 gallons out of an 11 gallon tank is just not enough if one expects to practice dispersed camping. But I finally found the time over the last two days to remove the protective corrugated plastic cover from the underside to take a look and see what might be the problem. Here's what I discovered.

1. The outlet is at the front bottom of the tank, where I expected it to be. 
2. The tank is not level side to side. I wasn't expecting that.
3. The tank is 1/4 bubble tilted to the rear after leveling the unit. I wasn't expecting that either.
4. Our tank is quite flexible and seems to have developed a permanent sagging point about 14 inches in diameter. This one really surprised me. Maybe the tank is 
    actually formed that way and since it is obviously the lowest point the drain should be located there.
6. It is a scary thought to be thinking of cutting a new hole in that low spot.

So, I decided to run a brace bar under that low spot. I found a scrap piece of metal stock that was T-shaped and modified it to fit under the slope. The results have me quite pleased. Before this was done the most I could get from the tank in a level use position was 9 gallons. Always 2 more that could only be drained by cranking the front down all the way. That's about 53 full turns on the crank.
After my modification I added one gallon of water to the empty tank. Double checked for level and opened the drain valve. The valve stopped dripping just shy of 1/2 gallon. So I cranked at down all the way and got almost all of the gallon out. 

Now I must state that this might be a unique situation and that if you go looking for yourself you could just find something quite different. 
As for now I will try this setup out at the end of the month and hopefully be able to report that i won't be drilling any holes. 

Attached picture will help you see what I did. Remember, there is almost always a solution to a problem.
I have more picture that show how the tank was not level and warped but it seems I can only post one. This one shows the bar in place.  

BrianZ

Interesting mod, @mnmarkiemark.
So the mod gets you an extra half gallon of water as I understand it.  And how is that brace held in place - is it welded or fastened somehow?

mnmarkiemark

I had just one gallon in the tank when the drain valve was opened. Almost half drained out without lowering the front of the trailer. Almost all of the rest came out when I lowered the front all the way down. 
For now the brace is just held in place by pressure. I'll add a adhesive if needed.

mnmarkiemark

Here is a photo showing side to side level. You can also see the warp in the tank. This is from the rear of the tank

mnmarkiemark

This is what the brace looked like before installing.

Dutch061

@BrianZ, actually @mnmarkiemarkwill go from around 9 useable gallons to 11.5 useable gallons based on the 1 gallon test. Which means about a 22% increase n available fresh water if it holds true. 

Brad

mnmarkiemark

Photo of the bulge, about 14 inches in diameter. I circled the lowest point for a possible future drain location just in case this brace doesn't really work like I hope it will. The silver looking piece is the aluminum angle bar that the corrugated plastic attaches to. Must of the bulge is rear of the axle. I do wonder if the tank is molded this way to provide a low point for a drain.

mnmarkiemark

Level showing almost a 1/4 bubble slope after the trailer has been leveled for normal use. Held the level against the outer tank edge to avoid the tank distortion. Slope is towards the rear, away from the drain.

mnmarkiemark

This is what the front of the tank looks like. The outlet at the bottom feeds the water pump and acts as a drain. You can see how the tank rests on the axle when there is water in it.  Notice the gap on the outer edge between the tank and axle. This gab was not equal on both sides making me think it is not level.

mnmarkiemark

Possible solution if a new drain location is needed. I found this on Amazon. It's called a Uniseal. Got a pack of 2 for about ten dollars. This one has a 1/2 inch pipe through it. I made this test piece to see if it really would hold. The nylon sheet I used is 1/8 inch thick. Used a hole saw to drill the plastic, trimmed it up a bit and inserted the seal. It is hard to push through, even with a soap lubricant. Appears to make a very tight seal in the 1-1/4 inch hole. Next the 1/2 inch pipe was inserted. Took a lot of pressure to get it in. Inserting the pipe caused the seal to flange out. It is extremely difficult to pull the pipe back out. I don't really want to drill a new hole in the tank but this will be the next thing I try if the brace doesn't work out. Anybody out there that has used this type of seal?   

rfuss928

mnmarkiemark 
Didn't taking the bulge out of the tank actually reduce the tanks volume?  I would guess that the usable volume remains the same because the volume of the bulge is wasted in the original configuration or non-existent after the brace is installed.   Just my thoughts FWIW...
Have fun, Bob

mnmarkiemark

Thanks Bob,
I have considered that possibility. I will complete several full to empty tank measurements to verify any capacity changes by adding one gallon at a time to verify capacity, emptying the tank at standard level operating position and then lowering the tongue all the way to see how much is left. Should have that data posted in a few days.

BrianZ

Yep, that's what I was thinking, @rfuss928.
Raising the back end of the tank might recover more water, but the tank probably needs adequate support along all edges.  Testing with a full tank might give a more accurate result of what is really happening with regard to total usable volume.

ScottG

Interesting discussion. The bottom of my tank bulges in the opposite direction, with a hump where the tank looks a little squeezed over the axle. This--combined with the fact that the tank itself does not seem have a natural low point--seems to contribute to the inability to completely drain the tank.

As I think about it, another contributing factor may have nothing to do with the shape of the tank at all. I vaguely recall a discussion about vortexing near the tank outlet that causes the pump to draw air and loose prime long before the tank is empty. I know mine will stop pumping when I can still visually see an inch of water in the tank when the trailer is level. I can't quantify my observations as I've never actually measured usable capacity. I usually have a fresh water source nearby and just make do by topping the tank up every couple of days.

mnmarkiemark

 Checking for vortex is something I have not tried yet. I just finished my last measuring test. This time I filled the tank while attached to my tow vehicle and drained it while is was still hooked up. See the attached photo for what was recovered, the 11th gallon is pictured, water about 1 inch from full. Since the tank is now empty I will go ahead and add two gallons, representing the amount I could never get out at normal operating level. This could be interesting!

mnmarkiemark

Scott G. mentioned a possible problem with vortex created by the water pump. Since my tank was empty after the last test I figured it a good time to see if I also have a vortex issue. I added two gallons (representing the two gallons that could not be easily used before my modification) to the tank and captured the water from the sink. Got all two back before the spitting and sputtering began. Next I added one back in and ran the pump again.  I got that all back too. Can I believe there is no vortex issue?  Now my biggest concern is that the Uniplug will wiggle loose and I'll have to go back to square one. Plan is to use the endoscope I have to spy on it occasionally. Fortunately there are three hole punches in the rear frame (thank you nuCamp) and I can easily slip in the scope and check it out. Tried it already after taking the T@B out on some bumpy roads. Looks fine, hope it holds for our upcoming trip. I'll post about our experience when we get back. Above is a rather poor photo of the seal taken with the endoscope. I think can get a better image if I take the time.

ScottG

Nice work, @mnmarkiemark. Maybe changing the location of the tank outflow also altered the flow in a way that mitigated any vortexing (if it was even an issue in the first place).

FWIW, I found that discussion about vortexing. If you read through @TNOutback's comments you will see the suggestion first came from nuCamp. 

mnmarkiemark

Thanks Scott, 
I contacted Creed at nuCamp to let him know about what I was working on. He is interested in seeing the photos and willi send them to R&D. 

ScottG

As an aside, I found this old photo while commenting on another discussion. You can almost see how the bottom of my tank bulges up in the center. 

mnmarkiemark

Very similar to my setup. I was lucky to have such a pronounced bulge on the rear side. I didn't realize how large and deep is was until the cover behind the axle was dropped down.

ScottG

Yep. The covering wasn't added until later years, so I have an unobstructed view of the tanks and associated plumbing in my 2015. Frankly, I like it that way. I'm in my seventh season and see no ill effects of not having that cover. 

mnmarkiemark

The covering is good if you aren't going to make any mods.  It is not that difficult to remove or at least drop down some to take a peak at stuff. My first experience was about six months after we bought it. I decided to add the boondock axle. Thanks to the great information on the forum the installation went pretty smooth. That is when I found out how flexible the cover is and that it could be rolled back on itself