Sundance 241BH - Black water tank fell out

[bedpan]

Hey Folks,

Got a new 2018 Sundance 241BH. We picked it up a few weeks ago and just finished up our first trip. We drove from the Toronto area down to Cape Canaveral Fl. In total 5050km including some driving around down there not hooked up. The first day we pulled into the park I went about setting up and inadvertently connected the fresh water hose to the black water flush out. A few minutes later we heard a loud bang and shutter to find the black water tank sitting on the ground.

Fortunately the toilet had only been used for a couple emergency pee's on the drive south so there was no major mess to clean up. I was able to put everything back together and it all appears to be working fine.

What I am wondering is why the tank would fall out. As far as I can tell the tank pressurized and swelled. When it swelled it got narrower as it got taller and fell from the brackets holding it in place. There did did not appear to be a lot of water in there. Far less then the 30 gallons that it should be able to hold (saying that I am not positive though, maybe it was 30 gallons). The tank itself was not damaged at all the brackets holding it were not bent at all.

In my mind the tank is vented to the roof. Should the tank not filled to capacity then turned the trailer into a water feature spraying water out the vent? Is there some sort of check valve to prevent this?

What I am really wondering is there a venting issue that needs to be resolved now?

Any thoughts are appreciated.

As a side note I have not refilled the tank to capacity to confirm the brackets are able to support the weight. Due to our only being in Fl for a 5 nights I thought it best to leave it alone. Come spring here I plan on filling the tank to capacity to confirm it will not fall out. Also there the fresh water tank which is 44 Gallons has bars underneath it to support it where the grey and black tanks do not.

Side side note.. Seeing the tank laying on the ground it reminded me of this video "front of the boat fell off"

Why did the tank fall off?

[bedpan]

The tank itself is secured on two sides. There are 'L' shaped brackets that run between the frame on either side. The edge of the tank sits in the 'L'. Pulling down on the tank from underneath I could not get it to flex enough to pull between the brackets. It appears to be quite secure. Hence my thinking it did not fall out due to weight and that it had to of swelled. As it swells to the top and bottom it would get narrowed and then fit between the brackets.

The other poster suggested testing out the vent. I can access the vent pipe where it attaches to the tank inside the trailer. Its in a cubby behind the hot water tank.

I am not sure which option I prefer... The tank filled/overfilled and dropped out, or the vent pipe did not vent and the tank swelled. Clogged vent should be easy enough to fix. Tank falling out I would bring to the dealer and tell them to fix...

bedpan wrote:

Lynnmor wrote:
It does sound like a venting issue. Try removing the vent cap on the roof and fill the tank from there, if the water soon backs up you found the problem.

I like the idea... Is there no sort of check valve in there though? In the bit I can find it is just a straight pipe to roof. So water in the vent should answer that question. Ear to the tank underneath should hear it hitting..

Worth a shot...

[bedpan]

Lynnmor wrote:
It does sound like a venting issue. Try removing the vent cap on the roof and fill the tank from there, if the water soon backs up you found the problem.

I like the idea... Is there no sort of check valve in there though? In the bit I can find it is just a straight pipe to roof. So water in the vent should answer that question. Ear to the tank underneath should hear it hitting..

Worth a shot...

[dougrainer]

While not common, this sometimes happens. It is not the vent causing the problem. It is the design and how your tank was installed. The mount brackets were either not designed correctly or the production line failed to secure them correctly. Usually, the fix is to install heavier gauge brackets. Doug

[Lynnmor]

It does sound like a venting issue. Try removing the vent cap on the roof and fill the tank from there, if the water soon backs up you found the problem.