I have read it MANY places online that GE silicone 1 is safe to use on aquariums. Before I started using it tonight on my DIY PVC overflow I read the directions on the tube and it specifically says "not for use on aquariums or below water lines. Which is it? Can I use it or not? I sure as hell hope so or I just wasted $35 in PVC parts.

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75 Gallon Planted

do not use it!!!!!
I would only use regular PVC cement and let the assemblies air out for at least a week before using.

I would never use silicone sealant on PVC connections unless it was aquarium grade and list for use on aquariums.

So I basically just threw away $10?
BTW, are there such things as 1" x 1" x 2" PVC tees?

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75 Gallon Planted

Yes depends on what configuration.

GE Silicone I is 100% safe for aquarium use.

Now bonding PVC, might be an issue but I think it will be just fine as I don't believe it will be under too much pressure.

Basically what I did was joined the PVC on my overflow to keep it from sucking air. the only pressure that is on the PVC is the water weight that is on the joints from it hanging off the back of the tank and the siphon that is in the u-tube. I don't want to, but if necessary I can rebuild it for like $10. I just don't want to have it fail on me or kill my fish. Here is what the completed overflow looks like.

There are actually two of these which are connected by about a foot of PVC pipe and connectors. it essetially looks like this.

Aquarium Gallery - DIY overflow

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75 Gallon Planted

If it said not for below waterlines, that to me says it will loose its seal over time. Ingredients for those products can change without you knowing, so what used to work yesterday may not today. I just used regular PVC sealants when I used for my wet/dry. I just let the connection soak in water for about 4 days and it was fine after. It stops leaching after a period. Hell, plumbers use it on our drinking lines. It better get safe after a period.

Sigh... I am really wishing I had not been so impatient and just used the pvc glue I had bought instead of throwing away materials.

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75 Gallon Planted

If it helps ya...here's two points of interest....

1) GE Silicone I is used all the time in resealing aquariums and making decor and backgrounds.

2) And you didn't hear this from me but.... GE Silicone I is the exact same product that is packaged as the Aquarium Sealant (which is sold for more $$)

I agree with James, I have used it to reseal tanks before and works just fine. GE silicone 1 and aquarium silicone is basically the same thing except packaged different and a higher price for aquarium silicone. GE 1 has to say not for aquariums because mainly and agreement between the 2.

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SUCCESS IS MEASURED BY YEARS, NOT MONTHS!!!
220 Tank build
http://www.aquariumforum.com/f15/sta...late-3253.html

Okay, So I just need to pay attention and make sure that the overflow doesn't fall apart. I don't see there being an issue with how I put it together because I was sure to use plenty of silicone when assembling it. I have not decided yet, but I think I might run a bead around each joint as well.

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75 Gallon Planted

Is this for the line that goes from the overflow to the sump? If so, why use hard lines? Rigid flexible line is much easier to deal with and comes with any wet/dry filter you buy nowadays. Allows you flexibility if you need to shift the sump around for any reason without having to disconnect later down the road. No sealant needed on them, but you can use clamps if need be.

I take it you guys (james and susan) have used it before? When you did, did it have the same label info mentioned above? I'm not saying you guys are wrong, but Im sure that if you've used it before it possibly was in the past. Couldn't the product have changed and now there is a product that is more suited with the same company? Might there be some reason why this info is on there now?

Yeah... The silicone didn't hold hardly at all. I did not even get it wet and the overflow practically fell apart in my hands. I am sure it was water tight but if there was any pressure put on the pipe then I am sure it would have been a disaster. needless to say I had to remove all the silicone and clean the pipes and fitting which didn't take terribly long to do. I am going to use PVC cement this time and hopefully I can get all the pipes set straight.

Lesson of the day: Silicone is not a good sealant for PVC.

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75 Gallon Planted

I have used it several times. Not only for sealing tanks but also for putting rock onto pvc to make caves. And that has been just a few months ago. It hasn't changed. And Ben your on TPT alot. There is an article building a rimless tank that the GE1 was used but since it was rimless he went to an industrial grade of it.

I know silicone will stick to pvc but I think you need to use a piece of sandpaper on it to rough it out before it will hold. That is how I did it.

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SUCCESS IS MEASURED BY YEARS, NOT MONTHS!!!
220 Tank build
http://www.aquariumforum.com/f15/sta...late-3253.html

I rebuilt the overflow with PVC cement and it turned out really nicely. Although the PVC cement is a pain in the ass to work with it is way sturdier and hopefully it is sealed. Now all I have left is the right side and the plumbing to the sump.
As for your question Jrman83 I am using hard lines down the back of the tank to about 18" - 24" above the sump and I will have a flex tube going into the sump. the reason I am doing it this way is because like you said, it will be easier to do maintenance and it is cheaper to use as much PVC as possible. Actually I just had a thought... I think I will run the PVC pipe as I just said then about 18" of flex tube to another PVC pipe into the sump. The reason I would do this is so I can easily lift the intake from the sump and still have a secure line that will stay in the sump without having to worry about the hose slipping out and causing chaos.

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75 Gallon Planted

I don't remember where but I read that it isn't as strong as aquarium sealant.

I will have to disagree with that,

when the proper PVC "solvent" is used it makes a chemical weld.
you have to use the primer to clean the PVC then use the solvent.

I would have to agree. A chemical weld is 100x stronger than a sealant.

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75 Gallon Planted

When using PVC or acrylic solvent Primer is not always nessary, and the bond is more like welding. It actually dissolves the material and melds it together as it dries. Making it impossible to take apart once dried and correctly joined.
Pretty much any 100% silicone (with no additives) can be used. You'll know your ok if it is food grade, and or can be used in kitchen or bath environments. I've used GEI and II, with no ill effects.
Preparation of any surface is important, and as Susan mentioned roughing up the surface can help. If there was any dirt, grease, oil, soap, it won't woke well. Wipe down with rubbing alcohol. Let all your projects that have 1/2" or less of silicone sit for min of 24 hours to dry and off gas....
Another handy item is 2 part epoxy putty, I recommend using aquarium safe if you have a "wet repair" as it is hard to tell all the ingredients in most putty's. (but again, the ones safe to use on drinking water lines are likely safe for fish). I also use JB weld quick, it is ok once it's dried.
And crazy glue is safe in any tank wet or dry, and will still bond wet.

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"Buddha in your tank"

I have to disagree with you as far as using GE silicone II in aquariums. GE silicone II contains mold inhibitors and another additives that are LETHAL to aquatic life. In other words, DO NOT USE GE Silicone II.
As far as using JB Weld in a tank, let's just say if that is all I have laying around then I will go to the store and get the appropriate adhesive.

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75 Gallon Planted