Basement floor rising when tanks full

[bogen2]

I got the water system running for the first time in my new rig today. Everything went well on the pressure side so I decided to flood the gray and black tanks to ensure they aren’t leaking. Filled up all 3 until water appeared at the drain in the shower and the kitchen sink. Filled the black tank until I could see water at the floor level.

I had been checking for leaks all along and there were none. But then I noticed that the short basement wall section with the cable and power receptacle was severely warped. Then I saw that the basement floor was bowed upward in the center. It was about an inch higher in the middle than at the edges, which caused the wall to warp. So I pulled each of the drain valves - the last one I drained was the bathroom gray tank and the floor flattened out again. So I’m assuming the full gray tank swelled up for some reason, which warped the floor.

I should be able to fill the tanks to their limits, so something must be wrong. Anyone else experience this type of behavior?

Bob

[bogen2]

Hmmm, no comments on this? Maybe a unique problem with my rig. Guess I better contact GD to get it checked out.

Bob

[TucsonJim]

I think we're all at a loss. I've never seen that reported before. It sure sounds like an odd problem.

Jim

[Gold Country Livin']

Sorry Bob, I thought that any past problem with a GD trailer had already been found by one of these forum users over the years because every time somebody has a situation, somebody else already had a fix! Love that! I guess this is a new one. When I read your first post the other day, it sounds that by adding several hundred pounds of water which you introduced on purpose with a hose, that created upward pressure on the floor. That means it likely also is putting downward pressure somewhere and or twisting. Neither is good. I am thinking broken strap, weld, missing support etc. The fact that there are no leaks is interesting in that if it did twist or move, it did not crack or loosen any fittings or pipes according to you (no leaks). That's my guess and at a start, they will pull the coroplast down. Let us know what is found. You have my interest now.

[bogen2]

So according to GD, this is expected behaviour:

Thank you for contacting Grand Design RV. In regards to the issue you are describing below, yes, the tanks in the unit will expand and if it gets over filled it will push up on the floor some. This is the reason when the tank reads full you need to drain the tanks before it gets to the point of backing up in the shower or sinks. There are areas above the tanks that we cannot add supports to because we have to allow for the tanks to expand so they do not burst or crack, etc. I hope this helps explain what you are seeing.

This seems odd - what if the basement is filled to the top. I can’t recall ever hearing about this type of expanding tank.

Bob

[jneubig]

Bob. I haven't filled my GD to capacity, but did do inadvertently do so on my previous toy hauler, an Open Range while testing the black tank flush (now I know why they say open the valve when flushing). I notice the same issues you are seeing with yours. The floor rose about an inch or so and went down as soon as the black valve was pulled. Mine was still new at the time and I was just testing all features before loading it down.

[aikenjt]

Hi Bob,

I just bought a 2021 303RLS and had the EXACT same issue you reported here on 4/26/2018. Did you ever get and answer from GD and if so, how was it resolved?

Thanks,
Jeff

[geotex1]

Hi Bob,

I just bought a 2021 303RLS and had the EXACT same issue you reported here on 4/26/2018. Did you ever get and answer from GD and if so, how was it resolved?

Thanks,
Jeff

It's an issue of beyond recommended capacity. The tanks are not meant to be filled to the point to be devoid of air space. This isn't specific to GD either, and you can always contact one of the tank manufacturers to verify. Anyway, the tank sensors are positioned such that the full position maintains a small amount of air space, and this is why the standard response of dump when indicated to be full. Remember as well, drains are gravity designed and intended to flow one way, meaning some of the threaded connections are not intended for backflow.

[goducks14]

Is there not an overflow hose? Seems like you could have a catastrophe if you for some reason got side tracked or something casued you to leave the hose unattended while filling.

[geotex1]

Is there not an overflow hose? Seems like you could have a catastrophe if you for some reason got side tracked or something casued you to leave the hose unattended while filling.

For the freshwater tank there is a vent, which will spill over. However, the OP was filling his black and gray tanks to overflow levels, which they are not intended to be. Doing so can indeed result in quite a mess in worst case scenario.