Black Holding Tank Loose?

[dgcarlson]

95 Lance camper Model 880. Holding tanks are covered with a large poly box/surround with insulation inside. When the black tank is full, I cannot push up on the bottom of the poly cover. When the black tank is empty, it's fairly easy to move the bottom up an inch. I'm thinking that at the far end (non-drain) the securing strap is broken and allowing the tank to rest on the bottom of the insulated poly box. Not good, but just wanted to confirm that the tank is not supposed to be sitting on the bottom of that insulated box. If my suspicions are correct, it sounds like a major job.

[dgcarlson]

Al,

Good suggestion. I'll see if the folks doing the repair have a similar idea. I had no idea those tanks would flex so much.

[Joe417]

It could be just your tank flexing down and touching the cover. It's most likely a polyethylene tank.

My fresh water tank flexes quite a bit when full. When empty it would still retain 2-3 gallons due to stretching of the poly when full.

While doing some work with bottom cover off, I added a support in the center of the tank to prevent it from sagging when full. Also helps to drain a bit more out when empty.

[dgcarlson]

Yes, the strap is visible at the cleanout end, and I wonder why they use those instead of a metal bracket with a rubber cushion? Taking it in to the shop next month for surgery -- no camping until after that.

[ksg5000]

I had something similar in my Class C - fortunately my tank wasn't hidden by underbelly which allowed me an easier inspection. Turned out one of the straps had broken (clean snap).

[dgcarlson]

Jerry, Okay, that could be it. But if a full tank vs. empty has a sag of an inch, that seems to be more the hangers, rather than the actual tank bending, wouldn't it? When the tank was filled, I could not push up at all on the poly box bottom, but when empty, it gives an inch. Cutting an inspection hole in the box sounds like a good next step - thanks.

[MFL]

I think a certain amount of sag is common on many holding tanks. Often times the holding straps are not enough to prevent sag. If only pushing the poly down an inch, I'd not worry too much. OTOH, most of these tank retaining systems can be improved on, if you want to take the time. You could cut a small flap in the poly, to better view the issue.

Jerry