Silicone the bulkhead!

[Richardsonic]

OK, there's a controversial topic. Here's my situation. I recently drilled two 2" holes for a modular marine overflow in a 210 gallon generic glass tank. I was momentarily distracted when drilling (trying to pour more water into the cooling dam) and I badly chipped the exterior glass when the drill jumped. The interior (water side) of the hole is fine. After plumbing the tank this is the only bulkhead that leaks no matter what I do. I have read extensively about sealing bulkheads here and other places so yes the flange side and gasket is in the interior, yes I cleaned the surface of the tank first with a razor and then iso alcohol, and yes I've made sure there were no cracks in the bulkhead. I even switched bulkheads on the two 2" holes and sure enough the same leak in the same hole but not in the other. That would indicate the issue is not with the bulkhead itself. I also have a gasket between the overflow and the exterior of the tank as recommended by Modular Marine. The only thing I haven't tried is tightening the bulkhead with a wrench of some sort because I cant find anything that has a large enough opening to grab the nut that also fits inside of the overflow. However I have a pretty strong grip to tighten by hand and that seems to be enough for the other hole. So...a couple of questions. Is this (so far) unfixable leak the result of the exterior chipping? I can't see why that would impact the seal on the interior of the tank. Secondly, the tank is worthless to me if I can't fix the leak so is there anything to be lost by applying silicone to this bulkhead to see if I can stop it like that?

 

[sde1500]

Certainly wouldn't hurt to try sealing it with silicone. Especially since as you say it is worthless to you otherwise. While I am not one to take too much risk with tanks and water, I like to show this pic from time to time about what can actually hold water. I've observed this tank holding water for the past 12 years, in this condition. I'd say a little silicone to cover a chip won't hurt.

 

[JumboShrimp]

I had 8 bulkheads on a sump system once where I went into 'overkill' mode-- I used a gasket on both the outside and inside, and I put silicone on the threads, and under each gasket. Tightened it all up with the nut and let the silicone squish out. Nothing ever leaked. So that's my 2-cents of a story. Best wishes. Let us know.

 

[JoshH]

So you seem to have it put together properly with the Flange/inner box/gasket/Tank/gasket/outer box/nut. The simplest explanation is the gasket between the tank and the outer box is not wide enough to cover the chip on that one hole and water is escaping around it.

You could use silicone but what I would recommend is getting a gasket sheet and cutting it to fit the entire size of the outer box. Drill two holes in it just big enough to fit the bulkheads through and install it between the tank and the outer box. This should seal everything and the benefit of it over the silicone is you can remove it and reinstall it down the road without having to redo everything.

 

[Doctorgori]

^^^^yeah there’s your plan.... try the two flanges/gaskets b4 you glue the thing .... they make a specific bulkhead wrench...I got one. I’ll go look real quick....

 

[Richardsonic]

So the followup then is the application of the silicone. With or without a gasket? Most examples I've read about say they put a bead on both sides of the gasket, tightened enough to keep things in place and then tightened all the way after 24 hours or so when the silicone has dried. It seems to me that at the point you're using silicone, the gasket is redundant and just a possible source of a future leak if it's floating between two layers of silicone. Wouldn't the seal have more integrity with just a judicious amount of silicone between the bulkhead flange and the glass?

 

[Doctorgori]

So the followup then is the application of the silicone. With or without a gasket? Most examples I've read about say they put a bead on both sides of the gasket, tightened enough to keep things in place and then tightened all the way after 24 hours or so when the silicone has dried. It seems to me that at the point you're using silicone, the gasket is redundant and just a possible source of a future leak if it's floating between two layers of silicone. Wouldn't the seal have more integrity with just a judicious amount of silicone between the bulkhead flange and the glass?

yeah, certainly the silicone would work but I’d bet so would 2 gaskets, worth a try , less messy/permanent

 

[Richardsonic]

I don't understand how the water gets past the initial seal inside the tank to leak out from the exterior gasket? The exterior gasket seems like nothing more than something to keep the overflow off of the glass and not really something that's designed to keep water in the tank. In other words, why is the chipped exterior impacting things at all?

 

[JoshH]

I don't understand how the water gets past the initial seal inside the tank to leak out from the exterior gasket? The exterior gasket seems like nothing more than something to keep the overflow off of the glass and not really something that's designed to keep water in the tank.

It doesn't leak out from the tank, it leaks out from the outer box. Because the chip is so big it prevents the gasket from sitting snuggly against the outer box and sealing it.

The side of the bulkhead with the nut and threads has no seal to it whatsoever so you need the gasket to create that seal between the tank and outer box to prevent that water from escaping.

 

[Millwright]

So the followup then is the application of the silicone. With or without a gasket? Most examples I've read about say they put a bead on both sides of the gasket, tightened enough to keep things in place and then tightened all the way after 24 hours or so when the silicone has dried. It seems to me that at the point you're using silicone, the gasket is redundant and just a possible source of a future leak if it's floating between two layers of silicone. Wouldn't the seal have more integrity with just a judicious amount of silicone between the bulkhead flange and the glass?

Follow the 24 hour advice. Basically you are creating a gasket that fills the irregularity and compressing it when you tighten it 24 hours later.

 

[Doctorgori]

^ ^^^ yeah that or there is a slight chance you can sometimes get a “ wicking” thing going on with the seal ... weird but it happens...you will see a similar phenomenon when you screw on a lid and even though the water level is below the cap,it still wicks out up the cap threads ... again gaskets can sometimes behave like that

 

[Richardsonic]

It doesn't leak out from the tank, it leaks out from the outer box. Because the chip is so big it prevents the gasket from sitting snuggly against the outer box and sealing it.

The side of the bulkhead with the nut and threads has no seal to it whatsoever so you need the gasket to create that seal between the tank and outer box to prevent that water from escaping.

OK, that kind of makes sense. But if that is the case, why wouldn't the recommendation be to put the gasket between the nut and the inside of the overflow? It seems like a more efficient way than allowing the water to seep down the threads and through opening to create a seal there rather than stopping it in the box itself?

 

[Richardsonic]

^ ^^^ yeah that or there is a slight chance you can sometimes get a “ wicking” thing going on with the seal ... weird but it happens...you will see a similar phenomenon when you screw on a lid and even though the water level is below the cap,it still wicks out up the cap threads ... again gaskets can sometimes behave like that

So your suggestion would be to not include the interior gasket when siliconing? Just use silicone between the flange and the glass?

 

[JoshH]

OK, that kind of makes sense. But if that is the case, why wouldn't the recommendation be to put the gasket between the nut and the inside of the overflow? It seems like a more efficient way than allowing the water to seep down the threads and through opening to create a seal there rather than stopping it in the box itself?

Water will seep through between the threads on the nut and the threads on the bulkhead, between the gasket and the threads on the bulkhead and flowing out between the outer box and the tank. There is no real way to stop it other than to seal the whole thing between the tank and the outer box.

 

[Richardsonic]

Water will seep through between the threads on the nut and the threads on the bulkhead, between the gasket and the threads on the bulkhead and flowing out between the outer box and the tank. There is no real way to stop it other than to seal the whole thing between the tank and the outer box.

I'll try a larger gasket to see if that works before I silicone. Thanks Josh.

 

[JoshH]

I'll try a larger gasket to see if that works before I silicone. Thanks Josh.

Any time! It wouldn't be the first time this has been used so it should work out well for you. The solid gasket sheet also has the huge benefit of supporting the whole outer box against the tank itself keeping it flush and supporting it much better than the gaskets do. Personally I think they should include a gasket sheet with all of these overflows...

And now you have a plan to try first and if it does happen to fail (Which I doubt it will) you have a backup plan.

 

[Richardsonic]

Any time! It wouldn't be the first time this has been used so it should work out well for you. The solid gasket sheet also has the huge benefit of supporting the whole outer box against the tank itself keeping it flush and supporting it much better than the gaskets do. Personally I think they should include a gasket sheet with all of these overflows...

And now you have a plan to try first and if it does happen to fail (Which I doubt it will) you have a backup plan.

Yes and now that we think the leak is coming from the exterior box that changes the calculation on silicone and where it might be needed if a larger gasket doesn't work.

 

[JoshH]

Yes and now that we think the leak is coming from the exterior box that changes the calculation on silicone and where it might be needed if a larger gasket doesn't work.

Hey @Richardsonic, just checking in to see if you've made any head way on this issue

 

[Richardsonic]

Hey @Richardsonic, just checking in to see if you've made any head way on this issue

I did! I ordered a sheet of neoprene rubber and used the drilling template that came with the Modular Marine overflow to cut the gasket material. The template is the exact size as the overflow so the gasket covers the entire space between the overflow and the tank. Most importantly not a single drop has leaked. Thanks for following up Josh and the key piece of information that the leak was actually coming back from the overflow down the threads.

 

[JoshH]

I did! I ordered a sheet of neoprene rubber and used the drilling template that came with the Modular Marine overflow to cut the gasket material. The template is the exact size as the overflow so the gasket covers the entire space between the overflow and the tank. Most importantly not a single drop has leaked. Thanks for following up Josh and the key piece of information that the leak was actually coming back from the overflow down the threads.

Awesome!!! I am so glad that you managed to figure it out and that the solution is working Now get that bad boy filled up!