Have I screwed myself?

InfinityARch

Exodon
MFK Member
Apr 1, 2018
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So I've just recently noticed that the seals on a 120 (2' x 4' x 4') gallon tank that's been sitting empty which I got secondhand are potentially in bad shape in at least one spot; I was able to get my fingernail underneath one of them and pull it a tiny bit, which from what I know is a sign that the seals are in danger of failing. The only saving grace here is that the glass is completely intact, because otherwise I wouldn't even need to ask the question.


Initially when I bought this thing I was thinking it wouldn't be a problem and I could just reseal it easy-peasy and be good for 5+ years, but after some reading cautioning me away from (large) used tanks I'm getting the impression it's not that simple with big tanks, and I'd have to completely rebuild the damn thing and redo the internal seals, then leak test it for ages to not have a ticking time bomb.

I'm also not sure I'm up to that; what little I can surmise from threads on the topic is that I'd definitely need a considerably better workspace than what I have available, which right now is my ground floor apartment, along with any number of tools I don't currently own. That means more $$$, and at this point I'm thinking it might be best to cut my losses before I flood my apartment and get my renter's insurance rate trippled; while they're prepared to insure the aquarium with a rider policy, I expect that will change the moment something goes wrong.

At this point I have a few questions I'm hoping the experienced hands here at MFK can answer for me:


1. From what I've described, are things as bad as I think they are?

2. Is it feasible for me to get this tank up and running without spending a fortune? I'm not afraid of having to work on it, but if it's going to end up costing more than say $200.00 just to get the tank into working order, I'm just about ready to call it quits.

3. How much would it be fair to ask for the tank (and the stand and the sump) if I'm better off cutting my losses? Obviously I would only sell it to someone intending to keep reptiles in it or willing to drop more money to get it into shape, but I'm still hoping (perhaps vainly) that I can recoup some of my losses.

4. Alternatively, if it wouldn't be exceedingly expensive to rebuild the tank (or if it is in fact safe to reseal such a large tank with the right technique), could anyone point me to some resources for this project? As long as it doesn't cost too much I'm prepared to put in the work.
 
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InfinityARch

Exodon
MFK Member
Apr 1, 2018
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An update: I think I may have overreacted; I can get my fingernail maybe a milimeter or two under one of the seals a few inches without too much effort, but I can't really pull it back from the wall of the tank, at least not without having to really dig in and probably hurt myself. I'm going to leak test the tank to be safe, and I'm still quite worried, but on second inspection I think I might be okay.

It's really beginning to dawn on me how much more complicated aquariums get when you start getting into large tanks.
 

appleton71

Exodon
MFK Member
Mar 13, 2018
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Appleton, WI
I've resealed the corners on a 125 without any problems. I cut out all the old silicone with a razor blade being careful not to cut into the joint and being sure to remove all silicone residue. Silicone won't stick to silicone. Most of the holding power is in the joint between the panes of glass, not the corner seals.
 

skjl47

Goliath Tigerfish
MFK Member
May 16, 2011
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safe to reseal such a large tank with the right technique
Hello; Most any tank can be resealed. I have resealed several. All eventually with success but a few took more than one try.

my ground floor apartment
Hello; Ground floor is much better than an upper floor. Structure likely to be better,. You will ot flood anyone down stairs when it breaks or leaks out.
I flood my apartment and get my renter's insurance rate trippled
Hello; Sounds about right.

have a ticking time bomb
Hello; All tanks, new or used, are potential disasters. A125 is enough water to do a lot of damage. Are you lucky enough to NOT have carpet?
I'm going to leak test the tank to be safe, and I'm still quite worried, but on second inspection I think I might be okay.
Hello; Leak test all tanks, new or used. Have it last as long as your level of anxiety. Say two days minimum.
I've resealed the corners on a 125 without any problems. I cut out all the old silicone with a razor blade being careful not to cut into the joint and being sure to remove all silicone residue. Silicone won't stick to silicone.
Hello; This. I have done the same on smaller tanks.

Good luck
 
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InfinityARch

Exodon
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Apr 1, 2018
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Hello; Most any tank can be resealed. I have resealed several. All eventually with success but a few took more than one try.


Hello; Ground floor is much better than an upper floor. Structure likely to be better,. You will ot flood anyone down stairs when it breaks or leaks out.

Hello; Sounds about right.


Hello; All tanks, new or used, are potential disasters. A125 is enough water to do a lot of damage. Are you lucky enough to NOT have carpet?

Hello; Leak test all tanks, new or used. Have it last as long as your level of anxiety. Say two days minimum.

Hello; This. I have done the same on smaller tanks.

Good luck

By ground floor I mean I'm literally on concrete under the flooring; there's no basement in this apartment, so weight is one area in terms of structural integrity that I'm not concerned about. It's also dead level, which is another potential issue that's out of the way.

I do have some carpeted areas, but also non-carpeted areas, and that's where the tank is going. I'm still concerned that it might not be good enough, but I've already cleared this with my insurer (and by extension the leasing company, their condition was that I was covered by insurance), so if worst comes to worst I won't be paying out of pocket for damage.
 
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InfinityARch

Exodon
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Apr 1, 2018
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So a bit of an update on this whole situation. I'm getting prepared for a leak test with the tank, so here's hoping that goes well. The other thing that I'm concerned about is the weight of the tank, but I've had the opportunity to get some of the details about my apartment's structure so I'm somewhat less worried.

I'm fairly sure my building's joists are SPF Grade #1 2"x10"s with a 12' 7-1/2" span length. That gives me a 50 psf safe limit at any point in the span, and I'll be spreading the weight over 3 joists and putting it against a bearing wall which I believe gets me up to a level where I'm looking at a decent safety margin even with the extra weight.
 

skjl47

Goliath Tigerfish
MFK Member
May 16, 2011
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Tennessee

InfinityARch

Exodon
MFK Member
Apr 1, 2018
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Hello; Are you talking about the same place in each of these posts?
No, I was originally going to be in a ground floor unit directly over concrete, but that didn't work out due to me be shifted to a different unit in the same apartment prior to actually moving in.

I'm now trying to determine whether it's still safe to have this tank in my apartment. I think the answer is yes, and my calculations are below. I'll find a professional to double check them for me ofc, but I don't seem to be in danger of overloading my floor.


So the tank consists of 0.5" glass, and it's 48" x 24" x 24". That comes out to a total volume of around 38.13 liters of glass when I factor the bracing.

38.13 L * 2.57 g/cm^3 * 9.81 m/s^2 * 0.22481 lbs/N = 216 lbs, rounded up to 220 lbs

The sump consists of 0.25" glass and is 36" x 12.5" x 16", corresponding to 8.04 liters of glass and adding 47.32 lbs to the total.


Wet sand has a density of 1.905 g/cm^3, and a 2" sand bed will take up 35.43 liters

35.43 L * 1.905 g/cm^3 * 9.81 m/s^2 * 0.22481 lbs/N = 148 lbs of force from the substrate plus the water required to saturate it.

Due to the height of the overflows, there will be about 1.25" of unused vertical space in the tank, meaning the remaining vertical volume is 24"-1.25"-2"=21" minus an addition .5" from the bottom glass, equating to 363.15 liters of water. Then there's the sump, which is 117.98 nominal liters with an internal volume of 108.34. Using a water level of 11.25" as specified in my design, that comes out to 77.39 liters of additional water from the sump for a grand total of 440.54 liters of water volume in the tanks.

440.54 L * 1.00 g/cm^3 * 9.8 m/s^2 * 0.22481 lbs/N = 971.21 lbs of water. To account for plumbing I'll round that to 1000 lbs.


The stand meanwhile weighs around 100 lbs, and I'll throw in 25 lbs of equipment.

That gives us a grand total of 1540 lbs of weight. That weight will be spread across 3 joists given the design of the stand, and as I said my joists are grade 1 SPF 2"x10"s with a 12.625 span. For a concentrated load at 1/4th span, the sheering force limit is 467 lbs/joist.

1540 lbs/2 (due to force being spread by the stand)/3 joists = 256 lbs/joist, giving me a safety factor of 1.82 against sheering, which is acceptable for wood framed flooring.

The maximum load of the segment of flooring in question is 12.625' span*4'*54 psf= 2727 lbs of force, though if we want to keep within the limits defined by the building code (which we do) it's down to 2020 lbs. The safety factor for the total strength is 1.75, which is once again acceptable.

Up against a wall, the center of mass of the aquarium's load will be 1 ft away from the bearing point.

1 ft * 1540 lbs = 1540 lbs*ft, which corresponds to a moment of around 513.33 lbs*ft per joist. The maximum moment at a weight limit of 40 psf is 1594 lbs*ft incidentally, so that's also not a problem.
 

skjl47

Goliath Tigerfish
MFK Member
May 16, 2011
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Hello; Do not recall if this has been discussed before but be sure to get renters insurance.
 
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