To Level ? Or not to Level?
This post is to all those who are worrying themselves sick because their tank is slightly tilted to one side and they do not want to go through the effort of emptying their tank to adjust the level...... A Post to save your lives :-) and also to all the rest interested :-) I have been doing some research on this topic as until recently i thought my 70 gallon was tilting to one side... that was until i found out that the strip of tape i had put along the rim of the tanks was not straight and i was comparing the water level to that :lol:
Note: i did not write this but obtained all the info from Here
Tanks don't need to be level. I make the following assumptions that can be verified by any physics book.
1. The pressure exerted by a liquid on a container's walls is equal in all directions at any given distance from the surface of the liquid.
2. The maximum pressure in a liquid filled container occurs at the bottom of the container
3. The depth of the liquid in a rectangular container will be maximized when the bottom is level with the surface of the liquid and the container filled to just shy of overflowing.
It follows that if a container is tilted such that the bottom of the container is not level with the surface of the liquid some portion of the container is unused as the liquid will spill out of the low side of the container before the container can be completely filled. The actual pressure at the bottom of the container is somewhat less than the pressure of a level container completely filled. Because the pressure is equal in all directions that means that the pressure can't be described as pushing down on the glass, rather it is pushing perpendicular to the wall of the container at any point, if you turn that container in any direction the direction of the force remains the same. I assume that any aquarium is capable of holding water indefinitely when perfectly level and filled to overflowing, this is when the maximum amount of stress would be seen at the bottom of the aquarium. Tilting the aquarium slightly would reduce the depth of the water and reduce the pressure, if the aquarium was designed to hold water with more pressure it won't break with less pressure.
I've been through this before and I already know there are a million websites that say an aquarium needs to be perfectly level. Go ask one of your professors how you would calculate the pressure on a container holding a liquid, then ask him what happens when the container is tilted, walk through the calculations yourself and come back and show me how you arrive at the conclusion that there is more stress on an aquarium that isn't perfectly level. Honestly I'd like to know, I've got an engineering degree and this is one of those things that no professor or text book could help me understand.
The model is accurate, the maximum pressure is on the seams at the bottom of an aquarium with the maximum height of water above the seam, see statement #1, it says exactly what you do about pressure being related to water depth. The maximum water height occurs when the tank is level, if the tank is not level the maximum water height is decreased which decreases the pressure on the seams. All vertical seams have a pressure gradient from zero at the water line increasing to a maximum at the bottom of the seam, these seams don't have any trouble resisting the unequal pressure. Again the largest gradient occurs when the water height is maximized as in a perfectly level aquarium, tipping the aquarium will reduce the water height and decrease the maximum pressure at the bottom of the seam.
I graduated 5 years ago, it's been a while since I've been close to anyone in the academic community who might be able to give me some additional insight as to why a level container sees less stress. The basic assumption I make is that unequal pressures are always present on vertical seams and they will withstand the pressure gradient without incident for 10 or more years, the seams at the bottom should be no less capable of carrying a load that is unequal especially considering the net impact of a reduced water height potential of a tank that is not level. The difference in pressure from one end of an aquarium to the other in an aquarium that has 1" drop over 48" would be equal to one inch of water or .03612 PSI (1 inch water = 3.612x10^-2 PSI at sea level) a fairly negligible amount of pressure. A water balloon with a latex wall of only a few thousandths of an inch thick will easily contain that amount of pressure without rupture. In my years of keeping fish I've never had a tank leak at the seams on the bottom where the maximum pressure is experienced, I've always had leaks somewhere in a vertical seam, every leak I've had was somewhere 3-6 inches from the bottom.
This one also got me thinking:
Please, everyone who wants to think about this problem read up on hydrostatics. Regular statics does not apply to liquid and gases.
The force on a surface of a liquid filled container is a function of the liquid density, gravity, and height of the water column. This is consistent with solid statics. However, the difference is not in the equation but in the force vector. The force of a liquid is not unidirectional with gravity, but it is omnidirectional. The force of the liquid on the container is applied in all directions equally.
Because the force is applied equally in all direction, there cannot be an imbalance of the force applied on the container. In other words you can not have "more" force applied to the side if the tank is off level.
Finally, I've read dire warnings that shimming is not to be undertaken lightly:
If you do decide to shim it, the shims need to be the length of the side you're trying to level tapered over that length. If you're doing the long side of the tank you need to do both front and back and the shims need to be the same size. If you're trying to do front to back you have to do both ends and the shims need to be the same size. You can't just stick a shim under the stand at one spot. It puts undue pressure on the tank and stand and could crack the glass.
I called two reputable LFS to see if there was a consensus. #1) Incredulously: “1/16 of an inch? A ½ is okay. You’ll never get it perfect. As long as it’s sitting solid on a stand.”
#2) “Start worrying at a ¼ inch, definitely ½.”
The best thing about having a level tank is never having to think about any of this.
another great read regarding this topic Right Here
Thanks fo going through and hope it helped ease some worries.
Ok so pressure is not a huge concern but what about weight?
How do you calculate how stupid a way out of level tank looks? :tease:
I doubt any of my tanks are perfectly level, most are pretty close. Of bigger concern is having the tank on a plane surface, with the perimeter evenly supported with a floating base design, and the whole bottom supported with a conventional design.
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If you're talking about the 180 in your other topic, standard base size on that is 24"x72". Your 3k pounds is spread over nearly 200 running inches of base, giving you a pressure of about 16 pounds per linear inch. Skip several inches of support, which the wood won't go up to reach, and you have a situation where the glass, which does have some flexibility, will try to flex down to. This flex causes an unstable situation, glass pulling apart at seams & such. Put a tank in a situation where the surface is bowed or twisted in some manner, and you have these stresses in several places, the tank is not designed to compensate for these stresses.
Not entirely all the way around the tank.
Nothing spans the 3 front & back legs? Every commercially made stand I've seen supports at least the perimeter, larger stands will have cross members to add stability to the stand. Ask Marineland if a stand that supports just the short ends & a strip in the middle would void their warranty.
Their own stand won't. It supports the perimeter. I'm wondering how many stands you've had experience with, unless Marineland has had an incredible breakthrough with tank building technology their tanks require support around the entire perimeter, and are still of floating base design.
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