silicone and bulkheads?

[donfishy76]

Why do some people silicone their bulkheads into the tank? I have seen this done sometimes and not in other situations. Can someone explain to me when to silicone and when not to?

[Blown 346]

People use silicon to ensure a proper water tight seal, that is mostly done with closed loop drilled tanks. In normal situations the supplied rubber gasket that comes with the bulkhead works fine.

[donfishy76]

well thats what i thought, but why silicone the rubber seal? if it is doing its job at sealing the water, then why use silicone?

[Blown 346]

I believe that the silicon is used on the bulkhead inside of the tank, just to ensure the gasket doesnt leak. Just another security reason.

[donfishy76]

Can you remove the bulkhead, clean up the silicon, and add a new bulkhead? Will this present any troubles?

[lakehorse61]

I ditto that question!

I bought a 265 custom acryllic tank that my local fish store glued/siliconed 45 degrees pvc elbows to the bottom of my tank bulkhead................awwwwwwwwwww........this along with many other f....kups.

when i realized all of this i fired them.

i want to get it corrected but my new people feel a good seal can not be acheived now because all of the glue could not be removed so they feel we will have to work the elbows.

kelly

[Reeforbust]

I used silicone on my bulkheads........I used the rubber seals on the inside of the tank, and silicone under my tank in the gap between the bulkhead and glass, then I screwed the nut on!

No leaks and I don't have to worry that later on it might start to leak.

If for some reason I have to remove the bulkhead, the silicone will pull right out and I can clean the residue with a razor blade and some denatured alcohol.

[jeffbrig]

Someone posted pictures on here a few years ago of a bulkhead they removed that had been siliconed just 6 months prior. The rubber seal had completely rotted and deteriorated, it was brittle and literally falling to pieces. What caused the rubber to break down? Vapors given off by the curing silicone.

So, if you decide to use silicone, just be aware that you may be defeating the purpose of the bulkhead seal.

My recommendation: buy high quality bulkheads with good seals and rely on them to work as designed. I have had no problem using Hayward Sch-80 bulkheads and they are only hand tightened. The seals on the bigger sizes are 1/4" thick. Once these are compressed properly, they do not leak.

[Reeforbust]

The rubber seal had completely rotted and deteriorated, it was brittle and literally falling to pieces. What caused the rubber to break down? Vapors given off by the curing silicone.



I WANT PROOF!!!!!!:hammer: :lol:

[lakehorse61]

my great professional used pvc glue on the elbows & glued down the screw on bulkheads with epoxy or gorilla glue or something.

no way to repair with out tearing up the acryllic tank.

[Reeforbust]

You can still get them out.........Just takes a whole lot more time.

You can also repair the tank if you do mess it up.

[schristi69]

Originally posted by Blown 346
I believe that the silicon is used on the bulkhead inside of the tank, just to ensure the gasket doesnt leak. Just another security reason.

The gasket is supposed to go on the inside of the tank. If they have it on the outside, then this is why they are getting leaks

[Highlander]

Originally posted by schristi69
The gasket is supposed to go on the inside of the tank. If they have it on the outside, then this is why they are getting leaks

Not necessarily so.
The gasket is meant to go between the flange and the glass on the opposite side from the nut. Inside or out makes no difference.
I have used both configurations without leaks.

[Reeforbust]

Originally posted by Highlander
Not necessarily so.
The gasket is meant to go between the flange and the glass on the opposite side from the nut. Inside or out makes no difference.
I have used both configurations without leaks.

I'm backin up Blown 346 and Schristi69 on this one........

Gasket goes on the inside of the tank.....nut on bottom of tank.

[jeffbrig]

Originally posted by Reeforbust
I WANT PROOF!!!!!!:hammer: :lol:

Sorry, I don't have any, just guesses. :D

Seriously, it had to come from the curing silicone. Either that or some chemical in the water that causes rubber to break down. Which do you think is more likely? :D :D

[Reeforbust]

I can see where that could cause a problem.........Maybe since it wasn't "in the water" they used a different silicone that worked for what they we're doing but wasn't compatible with the rubber??? I have some 100% silicone at work that will Burn your eyes if you get near it.....NOT FISH SAFE!!???

Who knows.........I just like to feel relieved that I went the extra step to eliminate any problems......Along the way, I might create some without even knowing it!!:eek: :)

[Highlander]

Originally posted by Reeforbust
I'm backin up Blown 346 and Schristi69 on this one........

Gasket goes on the inside of the tank.....nut on bottom of tank.

If you look at Aqua C skimmers, you will note that the bulkhead is fitted with the nut inside i.e. the wet side, and the flange and gasket on the outside, i.e. the dry side.

http://www.premiumaquatics.com/aquac/ev120.jpg


Or a Lifereef sump:

http://www.lifereef.com/lg_langlois.jpg

I believe these don't leak with this configuration.

Like I said, it doesn't matter. :)

[jeffbrig]

Certainly, there are a lot of variables. Here's an MSDS listing for Dow clear Silicone:

http://www.biosci.ohio-state.edu/~jsmith/MSDS/DOW%20SILICONE%20SEALANT.htm

Some intersting points lifted

Appearance And Odor: CLEAR PASTE W/ACETIC ACID-LIKE ODOR

Reactivity Data
===========================================================================
Cond To Avoid (Stability): WATER OR HUMID AIR
Materials To Avoid: OXIDIZING MATERIAL
Hazardous Decomp Products: CURING & ACETIC ACID VAPORS FORM. SILICON DIOXIDE, CO2, & TRACES OF INCOMPLETELY BURNED CARBON PRODUCTS.

Other Precautions: AVOID BREATHING VAPORS, EYE & SKIN CONTACT. USE ONLY W/
ADEQUATE VENTILATION. DON'T TAKE INTERNALLY.

Respiratory Protection: REQUIRED UNLESS VENTILATION IS ADEQUATE OR AIR SAMPLING DATA SHOWS EXPOSURES WITHIN TLV/PEL GUIDELINES. SUITABLE RESPIRATOR: ACID GAS/ORGANIC VAPOR TYPE. RECOMMENDED.



Unfortunately, nothing so bold as "curing silicone will break down rubber". Inconclusive at best....so we rely on anecdotal stories repeated on the internet. :D :D

[Reeforbust]

Originally posted by Highlander
[B]If you look at Aqua C skimmers, you will note that the bulkhead is fitted with the nut inside i.e. the wet side, and the flange and gasket on the outside, i.e. the dry side.


I am talking strictly on an aquarium which is what donfishy76 is talking about.......If the bulkhead is turned around on the aquarium, you would have a heck of a time getting the standpipe to fit. In a skimmer or sump, all your doing is letting water in so having the threaded part on the inside and the gasket on the outside is not a problem, PLUS this is the only way you can put it to connect your piping to the bulhead........Yes there are exceptions to everything.

:)

[wakesetter]

the gasket always goes on the opposite side of the nut. Regardless of which direction the bulkhead is.

[Highlander]

Originally posted by schristi69
The gasket is supposed to go on the inside of the tank. If they have it on the outside, then this is why they are getting leaks

Reeforbust,
My reply was in response to the quote above.
This is not specific to the original inquiry about a tank.

[Reeforbust]

OK.........Sorry..........:)

Don't worry bout me........I just ramble and hope SOMEone is tuning in.....:lol:

[ezhoops]

Ok you could do what I've done, buy another gasket and place on each side. that way your side on both sides and don't have to worry about scratching, cracking glass.

.02 cents

[schristi69]

That would certainly work also and to me....would be the preferred method.

[ezhoops]

just another 29 cent gasket will do the trick and remember to only hand tighten. I've used BH both ways, gasket on outside/ gasket on inside, never leaked either way.

[glassguy]

as my name says glass guy for 28 yrs....would it help you all if I were to submit a gasket to Dow Corning for testing of a bulkhead gasket and if so which brand of bulkhead would you like to test? Dow does this for free for me, to test compatibility of their silicone and other products. Also I would sugest Dow 999 clear...?
feedback?
Reeforbust you also should be able to get this done through Missouri also , you are aware that silicone is not always compatible with all gasket material right?

[gstuman]

I feel sorry for ReeforBust on this thread for being the only voice of reason. The rest of the opinions seem to be supposition and innuendo. The real way a bulkhead works that 90% of the people that use them agree upon is that the rubber seal goes on the side with the flange not the nut; that's how it's designed regardless of pressure.

I've personally had bulkheads leak and I always remove them and add silicone everywhere but the rubber/glass interface and they never leak again inspite of the silicon glass off-gassing erosion theory that I was proposed in this thread.

This is basic stuff don't overthink it.

If everyone keeps analyzing everything else like they do bulkheads where will you all be when someone dares to bring up a protein skimmer or a calcium reactor. ; - )