Fresh Water Tank Fell Out

dbutler

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Aug 4, 2013
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I have a 2013 Salem Hemisphere 312QBUD and have not used the water system in a few years. Sitting on the driveway now. Connected hose to city water connection to flush system. Water did not come out of faucets. Noticed fresh water tank was filling and water running out of tank drain. Been a while since I have used the water system at all. The tank drain valve was open and water was pouring from it. The overflow line did not have water flowing. I turned the hose water off and let the water stop draining then closed the drain valve. I capped the overflow line thinking it needed to be plugged also. The water pump worked as the tank was filling with water coming out of faucets. I turned the hose water back on. I noticed the tank filling again. I was in the RV and heard a loud bang outside. I went outside and the fresh water tank had fallen out of the bottom of the RV dragging wires and propane lines with it. Tank has a crack around the bottom drain fitting but other wise intact. Angle iron brackets still intact on frame. Not sure what made tank fall out. Measured tank and bracket locations and it seems tank should have been trapped between brackets and unable to fall out. So many questions. Not sure about next steps. Any help appreciated
 
If I'm reading this correctly you had a hose attached, water filling the tank and the overflow line capped. Sounds like you overpressured the tank, it changed shape and it popped like a balloon.
 
You had the hose connected to the city water connection, correct? And hadn't used the water system in quite some time? A common issue is that the check valve at the pump sticks open and back fills the fresh water tank. With the overflow capped the water had nowhere to go and as a result, what was said above, tank overfilled and the weight distorted the tank and it popped....
 
Sorry for your troubles, dbutler, and welcome. Shame that this is your first post but glad you're here now.

It sounds like Sunseeker and Willhound are on the case.

City water filling the fresh tank sounds like classic stuck check valve in the pump (and if you haven't used the water system in a while, it's pretty much guaranteed to be a problem). Switch back and forth btw city water and pump, opening a faucet between switches will "exercise" the check valve by putting pressure on it in opposite directions and is a solid way to try to unstick it.

Water coming out of the fresh tank dump valve is simple the dump valve being open. Some people store with the valve opened, some closed. If you were running on city water with a check valve properly working, the fresh tank wouldn't have had anything filling it. Closing the dump valve dealt with this "leak," but it didn't address the faulty check valve.

Capping the overflow vent was a mistake (not sure how you managed this, I've not seen an overflow valve that could be capped). As Sunseeker mentioned, this vent also allows air to escape when the fresh tank is being filled/displaced by the incoming water. Capping it kept air from being able to be displaced, and the tank (which is large and flat, like a book) distorted (attempting to become "round" like a balloon). This is actually a real problem, in that overflow vents can become blocked or inneffectual for all manners of reasons, from blockages to being kinked (to owners unknowingly capping them) and the tank expands upwards and down.

Typically, if the tank is lightly suspended (and they are) and limited against the bottom of the floor of the coach, then the tank is forced to bow downward till it distorts so much that it is no longer held by the supports (when bowing - and gaining vertical height - the tank loses horizontal width).

If the tank is WELL suspended (and reinforced, which some new trailers are being, or if reinforced by an owner), the tank will attempt to expand *upward* and, as a result, can buckle (and break) flooring above it. Even very modest pressure into a closed tank will fill eventually it and can create a lot of pressure (have you seen the exhaust run jack bags, that inflate using the exhaust of your car?)

So:
  1. Bad check valve = fresh tank filling from city water.
  2. Closed tank dump valve AND overflow vent = tank effectively becomes a "balloon"
  3. City water pressure pumped up the tank like a balloon = tank deformed and it (plus its new water weight) popped it out of position and fell, striking the ground (and tearing out some lines along the way).
  4. Crack around the bottom drain fitting = (likely) from the drain fitting hitting the ground with the added water weight.
If you never EVER use your fresh tank, I supposed you can delete it and cap the fills to it, but I'd suggest you probably want the tank for the random chance to overnight (or boondock), plus resale value down the road.

My understanding is that fresh tanks are made from HDPE material that do NOT like repairs (According to Elkhart Plastics (Elkhart, Indiana), which supplies the RV industry with holding tanks, RV tanks are most likely High Density Polyethylene/HDPE), so you are likely on the hook for a new/replacement tank with fresh hardware.

During construction, tanks are laid into the frame from above and then the floor is laid over the top, so you likely have to have one of the angle iron supports CUT so that you can put a new tank back up into there from below. Then it's a matter of inspecting and re-installing anything the tank tore out on its downward fall. You might also take a look at the floor above the tank, and look to see if its ballooning upward did any subtle damage (cabinet frames cracked, floor out of position, etc).

Likely a big project, but not a complicated one.

Again, sorry for your woes. Just my .02, hope this helps.
 
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There are other ways the fresh tank can fill from the city water connection besides the check valve failing in the pump.

Do you have a Nautilus wet bay control center?

And, maybe doubtful on a 2013 model but a Showermiser valve set incorrectly can as well.
 
There are other ways the fresh tank can fill from the city water connection besides the check valve failing in the pump.
I suppose that's true, though - after looking at them 2013 312QBUD, and reading the OP's comment on age and usage - I'm putting money on this. How else might the fresh tank be filling from the city water connection for this particular model? I did notice that the OP said "The water pump worked as the tank was filling with water coming out of faucets" which leads me to believe that the city water was hooked up and pressurizing the system AND the water pump was on at the same time (generally a no-no).

Do you have a Nautilus wet bay control center?
Doesn't look like it. Looks like fresh fill and city water connection is on the off camp side between the two slides (see attached photo, and/or check this video at about the 3 minute mark). I'm not specifically familiar, though, so could be wrong. I'd love to learn.

And, maybe doubtful on a 2013 model but a Showermiser valve set incorrectly can as well.
Also true, though - as you point out - not likely on a 2013, unless retrofitted or installed (as the first patent provided to Gus was filed in 2015), and it looks like it was picked up by the industry starting sometime around 2017.

You're an excellent armchair diagnostician, and I always value your thoughtful and credible input. Can you point out additional thoughts to consider? I'd love to learn.

Just my respectful .02. I could be - and likely am - wrong.
 

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I have the same unit, covering up the breather tube was a no no, this allowed the tank to expand with the water and distort until it exploded. The bottom of the camper is fully covered, how did the tank ,'fall out'? with mine, the gas lines to the stove are under the water tank, on the underside of the hard plastic covering. When replacing the your tank and redoing the supports, would you attach pictures. My breather tube broke off and I would also like to add more supports to the water tank. the propane lines seem to be in the way and I am hesitant to cut into the covering at this time.
 

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