I talked to a fellow engineer and we tried to remember our statics classes. It might have something to do with how the water is sitting extended beyond the perfectly 90 degree vertical angle and it might be pushing its weight in the outward direction against the glass.
That makes sense. Now I understand why a tank is more likely to leak if not level.
leaky aquariums
Started by
Guest_Dan Johnson_*
, Nov 06 2011 11:43 AM
34 replies to this topic
#22
Michael Wolfe
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Posted 07 November 2011 - 03:49 PM
Now you're talking... out and down... levering the front of the aquarium off (if you exaggerate).
I did a quick calculation and if you are really un-level by 1 inch over a 12 in front to back tank that is almost 5 degrees of tilt... that's a lot for something that is 21 inches tall an weights 400 plus pounds... and with the water moving itself forward (because it is self leveling) I worry about that moving center of gravity as well. Not to be a statics geek (too late, I know) but that is the definition of falling over... getting your center of gravity outside of your foot print.
I did a quick calculation and if you are really un-level by 1 inch over a 12 in front to back tank that is almost 5 degrees of tilt... that's a lot for something that is 21 inches tall an weights 400 plus pounds... and with the water moving itself forward (because it is self leveling) I worry about that moving center of gravity as well. Not to be a statics geek (too late, I know) but that is the definition of falling over... getting your center of gravity outside of your foot print.
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#23
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Posted 07 November 2011 - 04:25 PM
Of concern also isn't just whether the water surface of the tank is level, but whether the surface the tank is on is perfectly flat. The tank can be level overall, but if the surface isn't flat (at least where the edges of the tank are), then uneven force is exerted (I'm sure there's a fancy physics word for this). Twisting/bowing, etc. That's where the styrofoam sheet comes into play - it helps imperfections in the stand surface even out.
#24
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Posted 08 November 2011 - 06:48 PM
Just finished leveling the tank.
Even if it doesn't prevent the tank from leaking, it was definitely worth leveling the tank. The hang on back waterfall filter had been really loud ever since I set up the tank. The moment I made the tank level, the filter went silent. Yay
Even if it doesn't prevent the tank from leaking, it was definitely worth leveling the tank. The hang on back waterfall filter had been really loud ever since I set up the tank. The moment I made the tank level, the filter went silent. Yay
#25
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Posted 11 November 2011 - 04:43 AM
The resealing process with silicon looks difficult to make, and there is always the risk that it leaks again. I'm not sure if this is worth all the work. I think I would also buy a new one. Maybe you can use your old one as a terrarium for reptiles? Or you can also sell it as a terrarium? This would be better than throwing it away.
#26
Guest_Dan Johnson_*
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Posted 13 November 2011 - 02:47 PM
Any recommendations on thickness of polystyrene and a good source for it?I don't know why anyone didn't point this out, but you are wasting your time if you don't put your aquarium on a flat surface. The fact that you have had several develop leaks is the give away. Tanks shouldn't leak, even quite old ones that have been taken care of.
If you can't make the surface pretty flat that put the tanks on polystyrene sheets at least.
Cheers
Peter
#27
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Posted 13 November 2011 - 03:48 PM
I have styrofoam sheets under some of my tanks for this reason. But I'm not sure I really believe this long-advised practice does any good.That's where the styrofoam sheet comes into play - it helps imperfections in the stand surface even out.
Some of you with a scientific bent jump in here.
Let's assume the "weight-bearing shelf" has a two degree tilt in some direction. We put in a layer of styro, and fill our 20/30/55/75/90/125 gallon tank. What logical reason is there for assuming that the styro under the "high" parts will compress more than the section under the "low" parts, so that the tank will become level? If anything, the tilt will cause more of a water column over the "low part", thus more weight, and MORE compression than would happen on the high (and lighter) section. Accentuating the tilt, rather than mitigating it.
Seems like a better idea would be to make a shallow pan somewhat larger than the tank's bottom area, put in an inch of sand, use a level on the sand to make a flat and level surface, then put the tank on the leveled sand and fill it.
Personally, I have never experienced a spontaneous catastrophic tank failure, and I don't think I've ever talked to anyone who had one that was attributed to the stresses of not being perfectly level. While it could be a concern for very tall tanks, for most tanks and situations I don't think there's a great need to be perfectly level for structural reasons.
#28
Michael Wolfe
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Posted 13 November 2011 - 08:22 PM
Good Question Doug... we have actually be talking about two different things... lets try to seperate them...
Level... Erica's tank was uniformly 'leaning' forward, becasue it was not level. This would not be fixed by styro under the tank. She did the right think by leveling the onject that the tank was sitting on.
Smmoth... if you pit a tank on a surface that is not smooth, but has say a ridge or some other surface imperfection, this could create kind of a pressure point that could casue a problem. In the worst case, it could even induce a twist in the way the tank sits, and this would put extra pressure on the silicon joints. This is where styro would help by evening the surface.
Unfortunately we have just been saying the tank is not flat... and that could mean either level or smooth... styro with help smooth the surface... it will obviously not help with level.
Level... Erica's tank was uniformly 'leaning' forward, becasue it was not level. This would not be fixed by styro under the tank. She did the right think by leveling the onject that the tank was sitting on.
Smmoth... if you pit a tank on a surface that is not smooth, but has say a ridge or some other surface imperfection, this could create kind of a pressure point that could casue a problem. In the worst case, it could even induce a twist in the way the tank sits, and this would put extra pressure on the silicon joints. This is where styro would help by evening the surface.
Unfortunately we have just been saying the tank is not flat... and that could mean either level or smooth... styro with help smooth the surface... it will obviously not help with level.
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#29
Guest_Dan Johnson_*
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Posted 14 November 2011 - 11:16 AM
I have been looking hard for polystyrene sheets and am stumped. Since use of the sheets is widely recommended for under aquariums, surely there is a good source. Help is much appreciated. Thanks!
#30
Guest_gerald_*
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Posted 14 November 2011 - 12:32 PM
Any building supply store sells styrofoam or generic equivalent "expanded polystyrene" insulation. You want styro made for insulation, which is stronger and not crumbly like the white styro used for cheap coolers and fish shipping boxes. 1/2 inch thick is fine for smoothing over small bumps in the stand and insulating the tank bottom. Since it's usually pink or blue, I wrap black duct tape over the edges before setting the tank on it, to hide the color and reduce the chance of chipping it later.
Being slightly off-level isnt much of a concern except in tall tanks (20"+ tall) as long as the stand is flat and evenly supported. TWISTING is the real seam-buster. Your stand & tank can be perfectly level, but if the four corners are not evenly supported you will have twisting stress that can pop an edge seal or crack glass. Styrofoam will do NOTHING to correct this problem.
Whenever I move a tank onto a new stand (or move stand to a different spot on the floor) I always put a few inches of water in the tank and test for twisting stress by pulling/pushing up and down (fairly hard) on opposite corners to see if there's any diagonal free-play. If there is, use thin pieces of hard wood or plastic (anything non-compressible) to shim it up until you can't rock it diagonally. It's BEST to shim under the stand, but sometimes you have to put shims between stand and tank, if the stand itself isnt flat on top. Putting shims under or atop styrofoam is USELESS because the styro will simply compress like Doug says.
Being slightly off-level isnt much of a concern except in tall tanks (20"+ tall) as long as the stand is flat and evenly supported. TWISTING is the real seam-buster. Your stand & tank can be perfectly level, but if the four corners are not evenly supported you will have twisting stress that can pop an edge seal or crack glass. Styrofoam will do NOTHING to correct this problem.
Whenever I move a tank onto a new stand (or move stand to a different spot on the floor) I always put a few inches of water in the tank and test for twisting stress by pulling/pushing up and down (fairly hard) on opposite corners to see if there's any diagonal free-play. If there is, use thin pieces of hard wood or plastic (anything non-compressible) to shim it up until you can't rock it diagonally. It's BEST to shim under the stand, but sometimes you have to put shims between stand and tank, if the stand itself isnt flat on top. Putting shims under or atop styrofoam is USELESS because the styro will simply compress like Doug says.
#31
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Posted 15 November 2011 - 08:39 PM
Ah, drat. You make me want to level the tank just to play it safe. *sighs* Okay, I will.
I agree with the physics professor, having been through a rigorous science curriculum myself; but surely you will be more at peace with the leveling. You want to ensure that the resulting surface contacting the bottom of your stand is flat even. Otherwise uneven pressures across the corners of your stand might damage it or cause it to warp.
I had a similar problem with a 30 gallon tank from end to end. I wound up leveling the house.
Best luck,
Guy
#32
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Posted 15 November 2011 - 09:29 PM
I no longer do. I thought about it in terms of statics, and how much force is on the vertical pane of glass pushing outwards. If the tank is level, the force is only the pressure of the water pushing out. But if the tank is not level, it's not only the pressure, it's also a component of the weight of the water. Here, I drew a picture:I agree with the physics professor...
Tilted fish tank.jpg 23.06KB
0 downloadsThat's what made me level the tank. The free paint stirrers worked well, by the way. I put two under the front of the stand, and it's level now even though my floor's not.
#33
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Posted 16 November 2011 - 08:37 AM
But the weight of the water is what the pressure is... those aren't separate things.
#34
Michael Wolfe
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Posted 16 November 2011 - 10:43 AM
But the weight of the water is what the pressure is... those aren't separate things.
Disagree... they are very different... Erica's diagram shows that from a Mechanical Engineering standpoint... the pressure on the front glass exists in the first case even though no water is pushing down via gravity on the front glass. In the second case there is both.
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#35
Guest_Irate Mormon_*
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Posted 01 December 2011 - 01:11 AM
I'm late here, but I just want to add that it doesn't matter if the tank is LEVEL, so long as the base is even. IOW, if the empty tank rocks on its' stand, then the stress on the base is uneven and it will crack/leak. If the base of the tank has solid support and it does not rock, then all is well..
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