Primary seal question

dent20

Candiru
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Mar 25, 2008
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So I'm getting ready to reseal a large tank I bought from a guy, who tried sealing it himself. I didn't realize it until I got to work on it, but he stripped and resealed both the secondary and primary seals. My question is, what happens once the primary seal has been stripped? I've heard never do it, but never why. Is the tank basically ruined now, or can I still apply a new secondary seal?
 

fishguy306

Peacock Bass
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Oct 24, 2005
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Are you referring to the primary seal ad the one between the glass and secondary in the corners?

If so, yes it is possible to reseal a tank completely. That said, it is a big project, the tank must have all the silicone removed and glass cleaned. The primary seal (between the glass) is the one that does the majority of the holding, it keeps the tank together. Thus if the tank is leaking this seal is compromised somewhere and needs to be stripped and reapplied.

It is possible to have a tank without the corner silicone, it is mostly there to protect the silicone between the glass. I would recommend it however. But it should be applied with the rest of the silicone so that it cures to the silicone between the glass.

How large is the tank? If it is a small one it may just be best to pick up a new one. If it is a large one I would be concerned having had someone else tinkering with it. Large tanks are not something someone new to tank building should be messing with, it can be dangerous.
 

dent20

Candiru
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Mar 25, 2008
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It's a 175. I'm not sure if he did the corners, but I know he stripped out the silicone between the glass around the rest of the tank. I didn't realize he did it all until I stripped out the secondary. It held for a few days after I bought it from him, but then started leaking in the back from the middle and one corner. I already have some construction grade silicon (RTV 100 series) to reseal it. I was hoping that would be strong enough to get the job done right.
 

fishguy306

Peacock Bass
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If he redid the silicone between the glass he had to strip everything out. What makes you think he had redone it?

Some here are going to disagree with me, but I would strongly consider tearing the entire tank apart, remove every glass panel and clean the silicone off of everything. Clean off the residue and rebuild the entire tank. I would not trust the previous owners silicone job at all if it is leaking. Honestly, it will be a heck of a lot of work, but I'd rather that than a patch job that may not hold long term. You have the right silicone for the job.

That all said, once again, I'd be hesitant if this is your first tank build. Have you built any tanks in the past? RTV skins over very quickly just to warn you.
 

dent20

Candiru
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Mar 25, 2008
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I've never built a tank. The biggest reseal I've done up until now is a 30 gallon. I can tell he did it all because you can see the silicone under the tank. It wasn't a real clean job. He also used black silicone so you can see it between the cracks now that the secondary has been stripped away. I don't get the impression he actually took the tank apart though. You can see where he pried the frame back, I don't think he took it all the way off.
 

dent20

Candiru
MFK Member
Mar 25, 2008
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Just so I'm sure I understand, the primary seal does the bulk of the work holding the tank together, correct? So if it's weak, the secondary, no matter how strong the advesive, might not hold.
 

predatorkeeper87

Potamotrygon
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Sep 8, 2014
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hope it was a good deal, an entire tank reseal isn't something you wanna do half-assed, and by the sounds of it, thats what he did. In my personal opinion, thats a nice sized tank and worth the extra effort to take apart and reseal correctly. if you are confident in your ability to put those pieces back together then I say dive on in. That tank won't hold for long if he really "re sealed" it the way you are describing.
 

fishguy306

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That is correct, the primary seal, the silicone sandwiched between the glass, is what does the holding and where the strength of the tank comes from. If the tank is leaking that means the primary seal is damaged and compromised.

The secondary silicone, the silicone pushed into the corners, primary function is to protect the primary silicone. It has very little holding strength due to its location.

So that is correct, if there is a leak, patching it with the secondary may not hold. It may for a little while but I would treat it like a time bomb. May last an hour, may last 10 years. From how you've described this tank I'd guess it'll be on the shorter side. If you cant get your money back then you really should take the tank apart for a full rebuild.
 

joe jaskot

Dovii
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Sep 16, 2011
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Some bad info in this thread. Think about it. Anytime a tank leaks, the primary seal is compromised. No need to take the tank apart. Just scrape out the old silicone, clean with acetone, and reseal.
 
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