How to seal a glass window into a concrete tank - expansion / leaks issues

[Leaky]

Hello, my first post!

I recently built a few concrete tanks. The largest being 21 feet long by 10 feet wide by 3.5 feet deep. It houses blacktip sharks and a few fish.

I have three glass windows in the tank.

After curing the concrete, the window grooves were prepared by painting the concrete with a clear expoy primer.

We then applied silicone sealant and inserted the windows.

It's been running fine since 2009. But we have a minor leak issue on this tank and one other.

When temperatures cool with the weather, minor seepage of water occurs at the lower corners of the windows. When the weather warms up again, the seepage normally completely stops.

I would deduce that this is due to concrete expansion and retraction due to the temperature.

I think a better way is needed to prepare the concrete before siliconing the windows in next time.

I am thinking of preparing the concrete with a slightly flexible epoxy resin before siliconing next time (instead of just using the clear epoxy primer that is a paint type material).

Anyone have similar experiences with concrete tanks and glass windows?

Any suggestions for the best way of preparing the concrete side of the joint before using the silicone?

Thanks and hoping for some good advice from here.

 

[wheatgerm]

http://www.monsterfishkeepers.com/forums/showthread.php?t=74523&highlight=10000
i believe he seals the concrete with pond coat then uses dow 712 to seal the acrylic to the wall... but dont take my word for it its been a while since i read the thread

 

[Ocean Railroader]

Could you post photos of these tanks being sealed up in that I'm planning on building a 1000 to 2000 gallon tank in my garge in a year or two.

 

[The1and only]

JohnPTC actually installed a stainless steel window frame then secured his window to that. If you look up Bill Wann's Reefzilla it has a picture on how he did his with out a frame, it is also the same way that it is done in public aquariums.

 

[Leaky]

Could you kindly refer me to the url of the Bill Wann image that you refer to, 1andonly?

I would like to contact the man himself as well, in case anyone is in touch with Bill?

 

[The1and only]

So here is his new thread that he started about the tank.

http://www.thereeftank.com/forums/f176/pictures-of-bills-system-149347.html

I would just E-Mail him from that site because the info on the actual build and sealing of the window is a thread on Reef Central which he is no longer a member of and a lot of the images are no longer working. He is still active on The Reef Tank.