TAB400 freshwater tank repair

Arkansas_Gary

I was filling water for a trip and something went wrong.  I kept hearing creaking noises coming from the trailer.  I assumed this was just the unit settling on the suspension from the increased weight.  then the noise became louder and constant.  I went in the trailer and found the floor bulged, I looked under the trailer and bottom was bulged.  no water was leaking anywhere and the overflow never opened.  I turned off the water hose and disconnected it and while I was looking at it trying to figure out what the heck was happening the overflow suddenly opened and water came pouring out.    I opened up the outside shower and turned on the pump.  I've only pumped about 1/3 of the water out and that's all I can pump out, it acted liked and sounded like it was dry. the frame that holds the tank is broken.  I'm not convinced the frame broke during this episode because I never heard metal break.  

the tank never ruptured, just bulged.  I don't know how the water intake is connected, maybe I pulled away.  Does anyone know?  Even if I take it into a shop I've got to get the water out to travel down the road.

Has anyone replaced a fresh water tank or any of its framing or supports?  I'm not sure if this is a repair I can make myself.

Is there a check valve that seized up on the overflow valve or did something crawl in there and make an obstruction?


sorry for the sideways pic.  this is the top of the tank.  looks like it was glued to the wood and was pulled away when the tank bulged.



plastic popped off from the bulge, I did pull it down some more to see what was going on.  This is as far as the water will pump down, you can see the level in the white plastic.

manyman297

Woah, crazy! Somebody either here or on the Nucamp FB had a similar issue but I don’t know what they found as the cause. I can’t imagine the overflow becoming obstructed by mud daubers but maybe? That’s a ton of pressure. As far as I know the overflow is just an open tube without a check valve but I’m not 100% sure. If there is a check valve and it failed then that would explain it.

Sharon_is_SAM

This event sounded familiar.  The overflow was obstructed.
https://tab-rv.vanillacommunity.com/discussion/11129/dont-let-this-happen-to-you-blocked-fresh-water-tank-overflow-with-nautilus-system

It sounds like your pump lost prime.  Try closing all the faucets, then try the pump.  You may need to prime the pump by attaching a short hose to the Nautilus intake and fill it with water then blow into it will the pump is running.

Arkansas_Gary

I read the thread.  Thanks.  I like his approach to guarding the outlets.  After I get this repair done I’ll do this.  I have mud dabbers around.  It was probably them.

bergger

Whoa is right!  From the description it certainly sounds like there was an obstruction in the overflow.  I read the post Sharon linked when it first came out and made me a bit paranoid.  We don't have mud daubers here but when I fill the tank I always make sure I can feel air coming out of the overflow.  I also have used a piece of wire to push up it to just double check.  Before next summer I'll be putting some screen over it. 

I hope the repair is not too terrible.  I'd contact NuCamp and get some information on how the tank is hung and hopefully you can tackle it yourself.  Also I wonder if the tube the pump uses to pull water out remained in place and when the tank dropped the tube is now above the water line and simply not able to pump out the remainder of the water.  What about just opening the tank drain valve?  That should remove most of the water.  Maybe elevate the door side of the trailer to get more water in the direction of the drain.  

Please let us know what is involved in this repair and how it goes.  

Arkansas_Gary

Still working on it. Here’s an update.  All this damage was done by water at 45 psi.  That is the water pressure at the house, it’s kinda weak.  I measured it with a pressure gauge .  The Rv shops are booked out 5 weeks… I noticed that the subframe is under a black material that may be intended as a weather proof.  When the tank expanded and pushed upwards it pulled the subframe through the black layer.  See pictures.  I’m not going to be able to pull this off myself and I rebuild motorcycle suspension and do engine valve spacing checks myself.  This is a design flaw,  let me explain…when a force comes along which requires something breaking you design it strong on the expensive side you don’t want to break (everything above the area above the fresh water tank, including the floor.) and weak on the cheap side so it will break there.  In this case it broke both ways and I’ve been told by Nucamp that it’s not safe to drive on the road in its current state.  The yellow markups showed the black layer that it broke through.

Arkansas_Gary

Here’s the update.  It was just under a $10,000 repair because of damage to the frame of the unit.  Covered by insurance under comprehensive so I had a $250 deductible.  The fresh water tank itself was reused in the repair as it wasn’t damaged even though it flexed and bulged to cause the damage.  Remember the pressure was only 45 psi, within the pressure rating of the system.  Don’t own an expensive unit like this without comprehensive even if it is paid off!

Hammick

Yikes!  Glad you had comprehensive.  What is the year of your trailer?  Looking at purchasing a TAB and wondering if they changed anything on the '23s or '24s

Yoshi_TAB

Hi, Glad you got it squared away.  Did NuCamp do the repair or did you get it repaired locally?

You post sparked my interest to check if I have comprehensive, which I do .  Never thought of that...just collision.  

Denny16

Yikes!  The power of water, which under pressure does not compress like air does.  The damage expanding water can do!  Whilst the input pressure was 45psi, the internal tank pressure seems like it was much higher, to cause this kind of damage.  

Gary must have a newer TaB400, with the Nautilus unit.  This setup has check valves on the water input, as do most in-line Rv pressure regulators, which keep the input pressure to 45psi.  However, the check valves, will prevent any back pressure relief on the water line, so the volume of water into the tank will continue until reach equilibrium. 

The obstruction on the vent hose for the water must have been something very hard and stuck.  As the Nautilus unit injected water into the water tank, without a working vent, the pressure built up inside the water tank, and it expanded as more water was pumped into it, until it reached the inout,water pressure, stopping the flow.  A tank rated at 45-50psi would not expand at its rated pressure.

if 45psi is the input pressure, and once the tank pressure reaches the input pressure, water should stop filling the tank.  So, what we are left with, is the water tank that is not rated for 45psi (even though the rest of water system is rated for pressure), but is a gravity fill rated tank, probably the same one used on the pre-Nautilus units, and not rated for any pressure greater than that created by a full water tank without any additional external pressure caused by a closed pressure fill system, used by the Nautilus system.  

Under normal working circumstances, the gravity, non pressure rated water tank with a vent should work fine, as long as the vent is clear.  Another plus for the older, gravity fill only system used before the Nautilus.  You could only overflow the tank and get water squirted back at you from water coming back out the fill port.  

Cheers

Mickerly

45psi is 45 pounds per square inch. Multiply the area of the top of the tank in square inches by 45 to get the total pressure. It's a bigger number than you think.

Arkansas_Gary

It’s a 2021 tab 400 boondock.  Fresh water tank isn’t designed to hold any pressure there is an overflow that vents to atmosphere.  This was clogged by a mud wasp in my case.  Insurance classified it as animal damage and covered it…Tank didn’t burst only changed shape and took the frame of the trailer with it.  This should be engineered with a weak point that breaks before the expensive parts break.

GrandmasKid

Was the dealer able to fix it? This has happened to me and I've got an appointment with my dealer in five weeks. Thanks for your posts. I wonder how many this has happened to.

Arkansas_Gary

Another person sent me a DM about it.  So three of us at least.

Arkansas_Gary

Yes dealer was able to fix it.   Happened in October fixed in Feb🥲

Arkansas_Gary

There was frame welding involved.  Im handy but not handsome.  I work on my own equip motorcycles cars etc.  I could do this repair in my wildest dreams…frame work is another level.

Bayliss

@Arkansas_Gary, your first photo in this discussion thread appears to depict the left rear support of the fresh water tank.  It also shows what may be a carriage bolt (round) type connection that was used to mount the black support band.  Do you know if that was simply mounted through the floor of the trailer?  It does not appear that bolt was attached to (or through) the trailer frame, so I am assuming the only support for the carriage bolt (which held the metal support strap) was the trailer floor - - - am I correct?

Arkansas_Gary

It was mounted through a piece of square channel.   There is a water tank subframe that runs between the main frame beams.  This had to be refabricated,  it was no match for a mud dabber clogging the overflow drain tube.  It was bent and the bolts started pulling through it 

Bayliss

Thank you, @Arkansas_Gary.

Looking closer at your photos, it appears that the square channel subframe was relatively thin.  I tend to agree with your suspicion that the subframe broke at an earlier point in time.  The head of the carriage bolt depicted in your first photo appears to have only been supported from above by the trailer floor underlayment, which presumably significantly contributed to the tank support failure.

In re-reading your posts, I noticed that you mentioned that the top of the tank appeared to have been glued to the floor underlayment.  What did you actually observe?  Was there glue residue present, or did you observe other indications that glue had been applied between the tank and floor underlayment?

GrandmasKid

Finally I can share some news. It took five weeks to get an appointment and they didn't look at it for a couple of weeks after that. On our '21 400 BD the problem was indeed dirt dobbers blocking the fresh water tank vent. The good news is the pop I heard only bent a brace and the tank is OK. The brace is to be replaced at an estimated cost of $1,400. The part has not come in yet.