Concrete tank help

WynandvL

WynandvL

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Hey everyone

OK we have a problem with our built in freshwater discus tank. This is my fathers baby and unfortunately I am the only one able to fit through the gap to get inside the tank:lol:. This means I have to do the work inside hahaha (Yes if you are wondering I am complaining:p). Now my problem is that the tank has sprung a leak, yet again, we have had this problem since the beginning of the tank 4 years ago. The tank will run smoothly for a few months but then it will start leaking(not much but enough to irritate the crap out of my dad). We tried fixing it, several times by emptying the tank(almost always losing livestock) but then after a few months it starts again. The tank is concrete with just a viewing glass pain that is siliconed into the concrete. The dimensions of the glass is 1.4m Width x 1 M Height and it's 1.2cm thick tuffened glass. The total size of the tank is 1.4 W x 1 M high x 0.8M in depth. it holds about 1120 Liters. The tank is also Fiber glassed. Any help with the problem please.
Thanks:thumbup:
 
were in the tank is it leaking, at he glass panes or other sides? corners or not?
 
1.2cm tuffened glass? 12mm? im sure there must be quite a bitof deflecion in that glass?
 
out of intrest my nano tank, 600 x 350 x 400 (L x W x H) is 12mm glass
 
The leakage starts at the bottom corner of the tank where the glass and tank meet, but gradually more leaks form around the glass. We asked the glass company what would be able to hold the stress and they gave us the 12mm. It's been holding up for 3 years now, so it seems OK...
 
if you take a straight piece of plank put it over the glass and see if all edges of the plank are touching the glass, just out of intreat to see if there isnt deflection.

it sounds like maybe the silicone isnt holding to the cement?
 
I did it, the entire plank touches the glass. I also think the silicone isn't holding, we used marine silicone, but you can actually see the water going through the silicone and move down to the corner.
 
what thickness is the silicone, as an example i think in robns ten ton tank he used silicone thickness off like 2.5 cm maybe even more.

I think sean Koekemoer would be best asked to help out here as he has done this a few times
 
I've already PM'd sean, just waiting for the reply. I would say the silicone is about 1.5 - 2cm thick on both sides.
 
have no idee dude. Conver to marine and redo the glass?
 
Hahaha , no it's going to be to expensive to convert to marine. The tank is a meter high that's some immense lighting and to hard to work in. We want to do the glass over but that's why I'm trying to figure out what would be the best to do. Thanks for the help
 
The total size of the tank is 1.4 W x 1 M high x 0.8M in depth
Click to expand...

Although it was designed to calculate all-glass aquariums, the same principles will hold true for a single pane, and using the glass thickness calculator (linked below) to evaluate your glass thickness gives a recommended thickness of 16.5mm if one assumes the water level to be at 950mm:

http://www.marineaquariumsa.com/general/glasscalculator.xls

At this thickness, the deflection will be around 0.5mm. The thinner 12mm glass will deflect more than this, perhaps enough to pull away from the silicone, or to pull the silicone away from the concrete... Also, keep in mind that as the glass deflects (bends), it will also become "shorter", leaving a minute space around it's circumference, and this could perhaps cause the water leakage.

I'm interested to hear what Sean has to say.

Hennie
 
Thanks for the input Hennie, my dad had the idea of taking out all the silicon and replace it with fiberglass resin. Will this work? Fiberglass resin when hard gives no space for bending
 
Annoying said:
Thanks for the input Hennie, my dad had the idea of taking out all the silicon and replace it with fiberglass resin. Will this work? Fiberglass resin when hard gives no space for bending
Click to expand...

i think this will make the glass shatter into pieces, as it will put tension on the glass
 
Fiberglass resin when hard gives no space for bendin
Click to expand...

It's the glass that's bending due to the water pressure, and as it bends, it pulls away from the edges (i.e. it gets shorter). Silicone can accommodate *some* movement, a lot better than fiberglass would - so no, I don't think that will work.

A thicker bead of silicone would be able to stretch better than a thin bead, so you could try to re-do the silicone with a thicker bead. If you do decide to do this, then also seal the concrete where you will be putting the silicone on with a good structural epoxy, and make sure that it is really smooth and even - this will give the silicone a better "grip", IMHO.

Having said that, I suspect that a thicker glass pane (16mm or 19mm) would be the answer.

Good luck

Hennie
 
Reef Maniac said:
It's the glass that's bending due to the water pressure, and as it bends, it pulls away from the edges (i.e. it gets shorter). Silicone can accommodate *some* movement, a lot better than fiberglass would - so no, I don't think that will work.

A thicker bead of silicone would be able to stretch better than a thin bead, so you could try to re-do the silicone with a thicker bead. If you do decide to do this, then also seal the concrete where you will be putting the silicone on with a good structural epoxy, and make sure that it is really smooth and even - this will give the silicone a better "grip", IMHO.

Having said that, I suspect that a thicker glass pane (16mm or 19mm) would be the answer.

Good luck

Hennie
Click to expand...


i agree with this, there are options such as the addition of diatamatious earthe and salts that could be added to the tank (after livestock is removed) and allowed to seep into the crack and fill it but this takes time and is not 100% effective.

i think hennie is spot on here. i have seen this at our aquarium where they use acrylic panes that allow for too much flex.

good luck this is a very annoying thing to try troubleshoot.
 
May i humbly hazard an opinion.....

is the glass stuck on the outside or is it built into a concrete frame?

I am pretty sure Sean has his in a concrete frame with a lintel above, if your glass is on the outside, just siliconed in place then i think this is where the problem lies.... the deflection as described by Hennie is causing the glass to pull out of position, if the glass was inside a frame, this deflection may not pull away the silicone. that being said IF the flexing is the cause as the general concensus seems to be, i would cut the glass out, and put in at least 15mm in a concrete frame or perhaps a steel fram raw bolted to the tank. Its asking a lot of silicone to hold onto concrete without a frame in place .
 
According to Den Braven marine silicone wont hold on concrete. You must use a product called Neutrel Cure that will bond with the concrete. You also would have to let it cure so that it does not let toxins into the water.
 
Annoying said:
The leakage starts at the bottom corner of the tank where the glass and tank meet, but gradually more leaks form around the glass. We asked the glass company what would be able to hold the stress and they gave us the 12mm. It's been holding up for 3 years now, so it seems OK...
Click to expand...

Pressure is more towards the bottom of the tank

Reef Maniac said:
The thinner 12mm glass will deflect more than this, perhaps enough to pull away from the silicone, or to pull the silicone away from the concrete... Also, keep in mind that as the glass deflects (bends), it will also become "shorter", leaving a minute space around it's circumference, and this could perhaps cause the water leakage.
Click to expand...

Agree with Hennie. Your glass is one main reason for this,even though it is "thick enough"to withstand the water pressure, it is not thick enough to prevent warping.

Another thing to remember. You say that it is fixed, only to start leaking a couple of months later, makes me think your silicone is not thick enough, Johan van Aardt mentioned it. The silicone (in a newly applied state) will hold the glass in place, but it will start "tearing" away the more the deflection you have- oh, and remember that deflection can also happen in days that is hotter than other days. And I believe most of your leaks occur in summer (Hoedspruit is hot- I lived there for 02 years)

Marine silicone is fine to work with, I applied mine very thick. But.... I fitted an Aluminum frame around my glass, which I epoxied into the wall. I then filled the gaps between the frame and the glass with epoxy, so that it has the same amount of pressure all the way around the glass onto the frame if deflection does occur:

Here is a couple of pics from my thread on how I did mine:


I made a recess in the concrete in front, fiber glassed as well as flow coated the recess:

tenk12.jpg


I then drilled holes inside the walls where the lugs (as shown in the pic below) went in, but first filled the holes with non shrink epoxy.

161120072061.jpg



As a matter of interest, I first taped the glass around the edges to prevent any excess silicone from getting onto the glass and leave a straight silicone line once the tape was removed:

171120072083.jpg


On the bottom pic you can see how i Filled the gaps between the glass and the alu frame with wet to dry epoxy. It created an even distribution of pressure all the way around the glass and it also helps to prevent too much deflection between the glass and the wall.With the silicone between the wall and glass, it prevents water leaks as well as allow for a bit of deflection for expansion and contraction in hot/cold days.

DSC00003.jpg
 
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