2020 T@B 400 Fresh Water Capacity Change?

TNOutback

I’ve noticed on the refreshed NuCamp website that they list the 400 as having a 22 gallon fresh water tank.  I thought it had a 30 gallon fresh water tank.  Is this a misprint or has the fresh water tank gotten smaller?

ChrisFix

I sure hope that's a misprint, because that's a big change in the wrong direction IMHO. 

Sharon_is_SAM

I wonder if that was done to reduce tongue weight?  

1968Healey

This is the sticker on the side of our 2020 Tab400.  113 kg == 113 L == 29.8 gal

Either the website is wrong, or the sticker on the actual trailer is wrong.

TNOutback

Thanks @1968Healey !  Nominally 30 gallons.  I have to think the website must be a typo.

ChrisFix

Sharon_is_SAM said:

I wonder if that was done to reduce tongue weight?  

The location of the fresh water tank doesn't add to the tongue weight...in fact it seems a full fresh water tank actually takes a few pounds off the tongue (at least in the 2019 and earlier models). 
Did the fresh water tank get relocated in the 2020 changes I wonder?
Would be really great to get a definitive answer on the fresh tank capacity from nuCamp...

Sharon_is_SAM

I will check on this.

Sharon_is_SAM

The 400 tank capacity remains at 30 gallons.  The measured usable capacity before you see sputtering at the faucets is about 22 gallons, so the factory wanted to publish what will likely be the owner’s experience.  

We had this experience with our CSS gray tank - it held 15 gallons level, closer to 19 when you raise the tongue.

TNOutback

Now this begs the question:  what is the secret to filling the tank to capacity?  Is there an air pocket in the tank that cannot be vented by the vent tube I wonder?

Verna

The tank can be filled to capacity, but you will have trouble emptying 30 gallons. That is why there are only 22 usable gallons. 

After about 22 gallons, the water will start sputtering and it may stop flowing. 

If you drain it completely, then the prime to the pump must be reestablished to allow for water to flow normally when not using city water. 

ChrisFix

What has been the experience for owners of 2019 and earlier models - is the 22 usable gallons the same as in 2019 and earlier, or is this new to the 2020 T@B 400 for some reason?
I don't recall ever reading any comments about not being able to use most of the 30 gallon tank before - which is why I wonder if this is a new phenomenon or not.

ecstatic

Verna said:

The tank can be filled to capacity, but you will have trouble emptying 30 gallons. That is why there are only 22 usable gallons. 

After about 22 gallons, the water will start sputtering and it may stop flowing. 

If you drain it completely, then the prime to the pump must be reestablished to allow for water to flow normally when not using city water. 

Seems like a fairly major design flaw if ~8 extra gallons of water is unreachable by the water pump at the bottom of the tank.  I feel like someone would have commented about this when they opened their low point drain and 8 gallons came pouring out of it after they thought they were out of water.  I'm very curious about all of this.

Sharon_is_SAM

The 400 capacity and usable volume have been the same since production.  

Does the tank run wheel to wheel?  Where is the pump outlet located on the 400?

TNOutback

Got this reply today from NuCamp on the tank capacity question.  (I must say those customer experience guys at NuCamp are awesome!). 

“The difference between usable water and capacity has to with the water pump. The pump creates a vortex when it is pulling the water from the tank, which means the pump starts to suck air before the tank is empty, causing there to be unusable water left in the tank that the pump cannot suck out and pump to your sinks/showers/toilets. Since there is a difference between capacity and usable gallons we decided it would be more helpful to let people know what they can actually use vs what the tank actually holds.”

Makes complete sense, and makes me wonder about other manufacturers and what they claim about tank capacities, because you know they would have to deal with the same situation.  I appreciate NuCamp making the change in their specs, since the easy thing would be to report the biggest number you can.  It says a lot about this company.

b407driver

Seems silly to be hauling 64 pounds of unusable water around.

davel4wa

That does sound like a design problem. If the trailer is not leveled, then I can understand. If the pump is creating a "vortex" then the water tank outlet needs a redesign to fix.
I keep seeing posts about having to prime the water pump but in 25+ years of RV ownership I never had to prime the pump as they are self priming. 

TNOutback

I’m not sure there is a fix unless there is a “vortex preventer” in some fashion, and this issue is not just a NuCamp issue; you can read it in a number of camping forums.  If the pump’s suction is strong enough, I can see it creating a vortex that rises upward several inches to the point it breaks the surface of the water level in the tank and starts drawing in air. This would be the case, I would think, in any set up.  In our former RV, I learned over time that I needed at least 10 gallons in the tank in order to have enough water for the pump to pick it up and flush the toilet.  (We traveled with about 10 gallons in the 50 gallon FW tank to have water to flush the toilet while on the road.). I think it lost suction somewhere around 5 gallons maybe, but I never measured it.

ScottG

The water pump is self-priming, but I think the phenomenon TNOutback describes--where a certain amount of water is required in the tank to get things started--confounds the issue a bit.

I had never thought about vortexing being at the root of this issue. I wonder if some sort of baffling in the tank or around the outlet pipe would do anything to reduce this...

davel4wa

If the output of the tank where it connects to the pump has a screen or some type of perforated device, the vortex effect can be eliminated or reduced significantly. 

1968Healey

Digging up an old thread here with some observations from this summers camping trips.  I do think the tank holds roughly 30 gallons as indicated on the sticker.  I haven't measured water going in, but that seems correct based on usage.

At the end of our trips, if we know the T@B won't be used for a couple weeks, we'll open the fresh water drain valve under the chassis.  We've done this twice now after running the water pump dry.

With the tank 'useable empty', the drain valve will still dump water for 10+mins on the ground.  I suspect that's the missing 8 gallons that NuCamp is now calling out.

I'm putting together a list of 'off-season' upgrades and figuring out how to get 30 gallons useable out of the freshwater tank is high on the list.  I hate the idea of pulling around 70+ lbs of water that I can't use.

ecstatic

@1968Healey: Out of curiosity, am I supposed to run my water pump dry before pulling my fresh water drain valve?

Sharon_is_SAM

Drain your fresh water tank first, then run your pump dry.

1968Healey

Looking for some input here on recapturing the ‘missing’ 8 gallons of water.

It seems like the easiest way to lower the pickup is by connecting a hose to the tank low point drain and hooking that into the input of the water pump.

Borrowing a photo here, you can see the low point drain on the left side (blue/white hose).

This looks almost too easy to do (5 feet of pex and a few fittings) - what am I missing out on?  I could even add a new low point drain with a T fitting so I don’t lose that functionality.

jameskuzman

A September 2019 article on NuCamp's website about winterizing T@Bs says this about the 400: 

• Step 10: Pour 4 to 5 gallons of RV antifreeze into the freshwater tank.

• Step 11: Turn your water pump on and open ALL faucets until antifreeze comes out.

If the water pump can't cope with 8 gallons of remaining fresh water, then this method of pumping antifreeze through to the various fixtures isn't going to work either. 

Something isn't adding up here...

Sharon_is_SAM

Good point!  Can’t you use a portable pump to add antifreeze to the plumbing without going through the fresh water tank?  4-5 gallons would be more than enough for that I think.

falcon1970

There doesn't appear to be a sump for the water pump intake.  Does anyone know where the intake is located?  The pump should draw from the top of the tank and the pickup tube should run to nearly the bottom of the tank.
I'm not buying the vortex theory.  The pump is just not that large.  And if it really is true that the pump creates a vortex then you should be able to "jockey" the pump to extract almost all of the water in the tank--depending of course on where the pickup is located.  Turn the pump off, run the faucet in the sink until the water flow slows, then turn the pump back on.  Repeat.  It would take some finite amount of time for the pump to create such a vortex and turning the pump off would allow the water to equalize again.
My guess is that the problem stems from the pickup tube not being near the bottom of the tank and it unports when the water level reaches a certain point--apparently 8 gallons.  How high that is above the bottom of the tank would take some calculating.
Does anyone know the dimensions of the bottom of the tank?

1968Healey

If you open the floor of the closet you'll see the water pump attached to the forward wall.  The hose on the drivers side just goes down straight into the tank.  It seems to be either glued or fastened in and I didn't want to pull it out, but that's the intake from the water tank.

The fresh water tank is roughly 24 x 52 according to other members who have added tank heaters.  Doing some quick math shows that if there are 8 gallons left and the bottom of the tank is ~1248 inch sq, then the pickup tub is ~1.5 inches from the bottom of the tank.  The whole tank is only 5.5 inches tall, so that's quite a bit.

The other option is to just install a bigger fresh water tank, but that seems like alot of work.

Before I go any futher, I'm going to refill my fresh tank, run the water pump until its 'dry' (sputtering and not really effective) and then measure how much water I can still drain out with the valve.  


@jameskuzman You are absolutely correct, something doesn't add up there.  Maybe they think the fresh tank hasn't been fully drained with the valve under the T@B?  I'm not sure.  Hopefully my experiment makes this a bit more clear.

atlasb

I for one, don't travel with a full tank of fresh water.  Even with 5 or more gallons in the tank, I have noticed some sway created by water sloshing side to side.  If I remember, the axle capacity is around 3500 lbs.  adding a tank of water eats into what you will already have extra and gets you closer to the max axle weight.  Also, a tank of water is adding to the already fuel consumption.  Even when we have to go on a tank of water at the site, we source the water close to our camp area.  Just my thoughts on the extra weight!

falcon1970

@1968Healey
OK so the pickup tube goes in from the top.  That completely refutes the vortex theory. 
231 cubic inches per gallon times 1.5 inches gives us the 8 gallons that the pump can't reach.  I wonder if there is an easy way to extend the pickup tube.  Guess I will have to "get out and get under."
BTW, when you drain your tank you will have to raise the off side (pax side) in order to completely drain the tank.  The drain valve sits above the bottom of the tank.  I'll bet it is also 1.5" above!
That also means that if you drain your FW tank after a trip by just opening the drain valve and then refill it for the next trip you still have about 8 gallons of "stale" water mixed in with the new water.

jameskuzman

Sharon_is_SAM said:

Good point!  Can’t you use a portable pump to add antifreeze to the plumbing without going through the fresh water tank?  4-5 gallons would be more than enough for that I think.

I'm not sure about a portable pump, but I don't see why not. Most folks seem to just pull the hose off the intake side of the water pump, put it in the jug, and let the pump draw it out of the jug. That method would probably get the job done with one or two gallons. 

jameskuzman

1968Healey said:

Before I go any futher, I'm going to refill my fresh tank, run the water pump until its 'dry' (sputtering and not really effective) and then measure how much water I can still drain out with the valve.  

Looking forward to the results of this experiment - it should be very telling. Thanks for stepping up and taking it on!