Freshwater tank, 2015 S-max (filling, using, draining)

glesieutre

First, a confession: We never used the water system in our T@B until a week ago.  We tend to prefer private sites away from noisy neighbors, and rarely have electricity, much less water or sewer. (But love that propane!) Perhaps this is a result of starting out as backpackers many years ago... 

We just spent a week at a campground that had no hot showers, so we thought it would be a good time to figure out the water system. We filled the freshwater tank at the dump station on the way in to the campsite. (Or so we thought.) In the end, we just barely got two birdbath showers out of that tank, which was far from what we expected.  I couldn't figure out what was wrong, except that perhaps the freshwater tank was much smaller than I thought. 

On our return, I communicated with nuCamp about tank sizes.  Evidently, there were some changes during model year 2015, but they thought the following: 
- fresh water, 11 gallons
- grey, 19 gallons
- black, 8 gallons
The records for individual trailers went with Little Guy, so it was also possible (I guess) that we had only a 5-gallon tank inside the cabinet. (We don't.) 

The black tank seems to be located in a recess directly under the toilet, and my measurements (approximately 21 x 15 x 6 inches), are consistent with an 8-gallon capacity.  However, I didn't know where the fresh water and grey water tanks were located. 

So I crawled under the T@B, where both the grey and freshwater tanks are fully exposed. Who knew? 

The grey water tank is 19 US gallons — says right on it! And it is contoured with a low point so as to drain completely (more or less) when the valve is opened. 

The fresh water tank measures roughly 20 x 36 x 4 inches (or just under in each dimension, especially with rounded corners). So that’s probably 11-12 gallons. However, it is not contoured at all, just brick-shaped, and long and flat to boot. 

Several factors make it extremely unlikely the full volume of the freshwater tank can be used: 

The fill port is not at the top of the tank. 

The vent is not at the top of the tank, and the vent tube is kinked hard — effectively blocked — as it bends around a propane line. I will have to figure out how to remedy this. (I will probably mimic @ScottG 's approach as shown in a photo in related threads 

https://tab-rv.vanillacommunity.com/discussion/10910/getting-fresh-water-tank-completely-full and https://tab-rv.vanillacommunity.com/discussion/10910/getting-fresh-water-tank-completely-full. (ScottG also has a 2015 S.) @Floyd67 's use of weed whip line to unblock the vent tube also looks interesting, but perhaps it's enough to blow into it once unkinked?) 

While the outlet from the tank is on the bottom of the tank, the bottom of the tank is flat. I can’t be sure that it’s level when the floor is, although that is perhaps the design intent. 

To get as much water into the tank as possible, it seems that the front of the T@B should be elevated as high as it will go, and the vent tube has to be clear. Even that won’t assure that the tank is full, but it should get much closer. 

I'm also interested in trying various 5-gallon jug and siphon / pump approaches mentioned at https://tab-rv.vanillacommunity.com/discussion/237/water-tank-filling/

To pump as as much useful water out of the tank as possible, the front of the T@B should be (slightly?) lower than the back, since the outlet is towards the front. The T@B should be level side-to-side, as the outlet is in the center of the tank. 

In addition, when level, the low point in the fill hose is below the inlet to the tank. To have a hope of draining the tank completely (say for winterization), the front of the T@B should first be elevated as high as possible to hopefully drain the fill hose fully into the tank. When water no longer comes out of the drain, the T@B front should then be lowered as much as possible to bring the water now in the back of the tank to the front, since the outlet is at the front. 

I think it’s impossible to drain it completely, so sanitizing would be really important. I doubt that a little water freezing in the tank would harm it. (I think @Michigan_Mike says this somewhere.) 

-George 

PS -- We also learned how to drain the grey and black water tanks. Much more straightforward if potentially messier. No problems, though. 

mona

Black tank is 6 gallons in a late 2015s max. 

ScottG

I agree with everything you said, and will add that not only is the freshwater tank in my 2105 Max-S "brick" shaped, it's also a bit pinched in the middle where it runs over the axle. This further contributes to the inability to drain the tank completely when the trailer is level.

I employ exactly the same tactics you describe: I tip the tongue up a bit to fill the tank, and down a bit to drain the tank.

Another suspected issue is that as the the tank level is drawn down, water will tend to swirl/whirlpool around the outlet. This results in air being drawn in, and the pump loses its prime even though there is still water in the tank.

The tank shape and position combined with the whirlpool effect results in a practical FW tank capacity of less than 11 gallons. For ten years I've had it on my list to measure the actual usable capacity, but still haven't gotten to it. Judging by the water I can see remaining in the tank once the pump start sucking air, I'm guessing it's closer to eight or nine gallons rather than 11.

These are shortcomings I've just learned to accept and work around in this otherwise great little trailer.

glesieutre

mona said:

Black tank is 6 gallons in a late 2015s max. 

Thanks for this great information, @mona. The 8-gallon number I came up was based on the maximum volume available right under the toilet (and was consistent with nuCamp's number). But the actual tank volume could be less, as you indicate. 

glesieutre

ScottG said:

I agree with everything you said, and will add that not only is the freshwater tank in my 2105 Max-S "brick" shaped, it's also a bit pinched in the middle where it runs over the axle. This further contributes to the inability to drain the tank completely when the trailer is level.

Another suspected issue is that as the the tank level is drawn down, water will tend to swirl/whirlpool around the outlet. This results in air being drawn in, and the pump loses its prime even though there is still water in the tank.

These are shortcomings I've just learned to accept and work around in this otherwise great little trailer.

@ScottG, Yes I read about your tactics in a couple of other threads -- make perfect sense. Thanks for the additional observations. I agree that it's a great little trailer.