Understanding Black Tank Shape

Question

Yesterday, I cleaned my black tank by using a wand. I quickly realized what I thought was the bottom of the tank wasn't. I think my tank is shaped like a pyramid or at least is higher in the middle. The tank is 30 gallons and I could easily touch the bottom of the tank with the wand. Not to mention it still looked empty after cleaning and when I dropped a chem tab in it shot off to one side. I always thought tanks were square or at least flat bottomed with a slope towards the valve. Ideas?

k_charles · Answer

I think 30 gal is about 4 cubic ft. that would make a 4 ft X 8 ft tank only 6 in deep.

donnier32 · Answer

K Charles wrote:I think 30 gal is about 4 cubic ft. that would make a 4 ft X 8 ft tank only 6 in deep.Good point. Is it possible or normal for the tank to be raised in the middle?

dewey02 · Answer

I don't know what yours looks like, but here are a couple of examples.It appears that most are sloped to the drain side, which makes sense.

ozlander · Answer

Mine are shaped like that except the drain is in the middle of the long side.

downtheroad · Answer

Shape can depend on size (number of gallons.)
Most often then are thin like about 6-8 inches deep....because they have to fit under the floor and between the frame rails...but not below the underbelly. Like the 3 on the left side of the picture below.

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