Filling fresh water tank to full

Bill&Suze · April 18

Today I began the dewinterization process by pumping 1/2 c. bleach in 3 gallons of water into the fresh tank followed by another 5 gallons (an additional experimental amount to test a flow meter which turned out to be very inaccurate.) The capacity of the 2024 400 is 25 gallons so with 8 gallons pumped in I then had to add 17 more to completely fill the fresh tank. Since this is the first time doing this I had to wing it in guessing when the tank would be filled without overfilling. We're cautioned to prevent overfilling which can damage the tank so it sounds like there is no overflow relief drain. I have a feeling that I didn't get close to full because I got nervous as time passed and shut water off when the sound seemed to be changing. I'd appreciate hearing how others determine when their fresh water tanks are full.
As an additional note, I thought of seeing how long it would take to fill a 5 gallon bucket with my standard hose setup used to put water in the camper. It took exactly one minute so theoretically I could fill the fresh tank in 5 minutes. Any suggestions?

webers3 · April 18

This is what I use, I trust it more than the tank levels. https://www.amazon.com/Save-a-Drop-P0550-Water/dp/B0058EOC5M/ref=sr_1_4?crid=1YZTKN278JZ3E&dib=eyJ2IjoiMSJ9.2OF6Ezk9EK44ZPYecQhfZntHwoRhNUync2vB9AuMP-Fw8tqU5pGzvuyAXmEOEKo-11e5hP-nkAAytICqtlWxzyxdcN3GoaPocMyL9GVVVo5sng7bLAf3EO75amnK8rWRKRsffbpDfJZjjSkjTV5CnZlp0sZTBjzmP1r4sfKwbVUoKxhc_D2OXS7aXm392_g1d8Ra-AIrhwNcWeG7XmdRFqzqLDLdzew_CbCHXrMFepQ.Z8EoN8_jxg5wD6-DCZolzqeud0tabREc6ZZ-oqvZ5vU&dib_tag=se&keywords=inline%2Bhose%2Bwater%2Bgauge&qid=1745016141&sprefix=inline%2Bhose%2Bwater%2Bguage%2Caps%2C136&sr=8-4&th=1

Gomers2 · April 18

Bill does your owners manual say "28 gal (25 gal usable)"? The indoor led level indicators are infuriating in their vagueness. I would like to think there's an overfill check valve, but I haven't had the guts to find out!

Bill&Suze · April 18

Thanks @webers3, that meter looks similar to the one I have but simpler. I'll take a close look at mine to see if perhaps the impeller is slightly jammed with debris. Someone leaving a comment about yours noted that his impeller was slightly blocked and its accuracy was affected.

@Gomers2, the owner's manual doesn't specify tank capacity. I understand that it's 25 gallons only because that's what nuCamp's web information lists for the 400. You're right, the level indicators are really vague and can't be used to determine when a tank is full. I guess that a dependable flow meter may be the best guide.

qhumberd · April 19

I have overfilled my 400 a couple of times with no issues. There is an overflow on my 2019. I just wait for the sound to change and then slow the fill flow. You can get pretty close but I don't see any damage potential as long as you are filling slow at the end. It is just a large plastic tank with the fill tube open to the air.

pthomas745 · April 19

Crawl under the trailer and take a tour. Somewhere down there you "should" have a "vent overflow". The air in the tank has to go somewhere when water begins to fill the tank. The "damage to the tank" will happen...and has happened...when the "vent overflow" gets clogged and the air cannot escape. The tank will simply expand and damage the trailer frame...and, yes, this has happened.

So...if anyone plans to try these types of tests ( we all have done it!) please be aware of what the actual damage could be in the newer Nautilus type trailers with the "vents" under the trailer.

https://tab-rv.vanillacommunity.com/discussion/11129/dont-let-this-happen-to-you-blocked-fresh-water-tank-overflow-with-nautilus-system

Here is the worst case:

https://tab-rv.vanillacommunity.com/discussion/17790/tab400-freshwater-tank-repair

If your vent is clogged, you will not get an "overflow". But, if you can still feel air escaping, there is still more water capacity. (This might be hard to sense, however.)

@Bill&Suze if you can get us some photos of the area under the trailer on the driver's side, we can help look for the "vent". I think there has been some changes to the design.

Bill&Suze · April 19

@pthomas745, thanks for the valuable information. I've taken a photo of what I imagine is the overflow vent for the tank. Now that I know what (probably) and where it is I'll try to run a zip tie through, although there's a 90 degree elbow on the tube down through the floor and it's a small diameter piece, so maybe a flexible wire. Then I'll run some more water and feel for air. It's helpful that it's so close to the Nautilus box.

Image: https://us.v-cdn.net/5021717/uploads/editor/an/9qnmhmfq5a1g.png

pthomas745 · April 19

Thank you for the photo. This is a NuCamp change from the open "round blue" drain spout in the trailers before 2024 or so. There are some photos of that blue spout in the other linked threads. I can't tell...maybe they just glued in a 90 degree elbow into the old "blue spout?" How big is the opening at the end of the fitting?

I have no experience with the insects that were reported in the other threads, but I'm assuming this would prevent that sort of intrusion?

It may be a bit difficult to "feel" a lot of air being vented until the tank is close to being full, so experiment and see what you find. Easy to me to say, I'm not the volunteer laying down there!

Bill&Suze · April 19

Here's a new wrinkle that became apparent today regarding the subject of filling the fresh water tank on the 2024 T@B 400 Boondock. This was my first experience needing to fill the tank to sanitize the plumbing so I was crouched down by the Nautilus for quite a while as the tank was filling with my hand close to the overflow vent to feel the very slight movement of air out of the tank. It's close to being imperceptible so I was concentrating hard trying to sense changes in the sound of the flow or creaking from the tank frame, all the while pretty sure that I could feel the air being expelled. I was completely caught off guard when the water flow suddenly stopped - it's as though the system has an automatic shut off valve to stop tank filling. The panel inside the door shows a full tank, there's no floor bulging, and water didn't begin spouting out of the overflow vent. Has anyone else corroborated this with theirs? If nüCamp has started to provide a shutoff in later models it's awfully good of them - takes the anxiety out of when to stop filling.

MarkAl · April 19

As stated above there must be a vent on the tank otherwise the tank would deflate or air would be sucked in the faucet outlet when the pump turns off. BUT if insects have stopped up the vent likely enough air would get through to keep the tank from being sucked smaller.

Note that since I'm sure we ALL use a pressure limiting fill device, the tank pressure could not continue to fill past this 40 - 45 psi limit. This also limits the pressure inside the bladder and connections when/if the hose flow capacity is greater than the vent's capacity to discharge water.

The final situation is why when I am filling the bladder, I reduce the flow rate as it gets close to indicate LED full lights. Since I also frequently forget I, in too many times, rush over to the hose faucet when I see the vent pouring water out. I would prefer not to stress the bladder more than necessary.

I doubt NuCamp has an automatic vent shut off (no water exits when full) as it's a potential failure mode and now forces the bladder and connections to accept whatever full hose pressure could be at which is pretty bad.

MarkAl · April 21

Ahhh fate intervened, I just proved myself wrong! I "thought" I'd reduced the flow enough to limit intake to less than the vent outtake. I got distracted and yep bladder expanded and broke the floor! Apparently minor overfills are not a problem but don't chance leaving it too long. I'll now be scheduling a floor replacement - probably NOT cheap or quick.

Bill&Suze · April 21

So sorry to hear of this mishap @MarkAl. You didn't mention structural damage so hopefully repairs will be limited to a floor replacement.
I, too, proved to be wrong about the stopping point when filling the fresh water tank. I had noted the first time that the water flow stopped at the filled point and wondered if nüCamp had installed a cutoff valve. Well, the second time I filled to rinse the chlorine solution the flow did not stop and the tank totally filled and water was spewing out of the overflow. Obviously the volume of water being put in is a lot more than the volume that is expelled due to the larger hose diameter as compared to the puny overflow tube. It's easy to see how the tank can quickly expand. Luckily I was able to quickly cut off the hose supply with an in-line valve I got just for the job. It's placed between a 3' length that is connected to the Nautilus intake and the long hose back to the house faucet, so it's easy to keep one hand on the valve control knob.

Jay_and_Kat · April 21

So a thought I had about this, would leaving one or more of the faucets open while filling the fresh tank mitigate the risk of overfilling by giving any excess water somewhere to go (in addition to the overflow / vent?)

Bill&Suze · 12:38PM

Jay_and_Kat said:

So a thought I had about this, would leaving one or more of the faucets open while filling the fresh tank mitigate the risk of overfilling by giving any excess water somewhere to go (in addition to the overflow / vent?)

An interesting thought. I would guess that if the Nautilus valves are set to the Power Fill positions, water is only routed to the tank. They'd have to be set to the City Water positions in order to route through plumbing lines to sinks.

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