HELP! leak test -> it leaks!


New member
i bought a 65g RR tank with 3 x 1inch bulkhead holes about 9 months ago, and put it in my closet. now im ready to finally put it together and did a leak test last night. It leaked around all three of the bulkheads AND from the internal overflow box(from inside the overflow box to inside the tank area) . Turns out i have the gasket on backwards. it was in the tank, but the soft side was pointed away from the glass.

So next i flipped the gaskets around, and that helped a lot. The Leaks subsided in two of the holes, and completely stopped in the third.

Next i used silicone on the edges of the internal overflow box AND around the inside glass surface of the bulkhead. When i went to leak test it tonight, one of the bulkheads is STILL leaking, the other two are now fine. likewise, the leaks from the internal overflow box to the tank have stopped ( up to 6 inches).

In other words, as of NOW, i have one leaking bulkhead. the reason seems to be because of the drilling, there are some chips of glass that are missing around the hole. normally i expect that the Rubber gasket should seal it, but no matter how i hand tighten it, its not enough. ( i didnt try it looser as well).

So, i wiped down the overflow box, have a fan to make sure things are really dry and going to try siliconing that last hole one last time. does anyone have any ideas that can help? any words of wisdom? and honestly if you can lend a hand and show me what im doing wrong, id really appreciate it.


Tang Salad

Algae skeptic
Are these new bulkheads, or the ones that came with the tank?

If they're old, replace them. The rubber can dry out and lose its sealability.


Premium Member
If they are new, put silicone on the gasket surfaces. Don't overtighten them or they break.

If they are not new, replace them.


New member
they are all new bulkheads, which side of the gasket is supposed to be touching the glass? smooth side or side with the ridges?

secondly, When applying silicone, do i put a circle bead around the entire hole and then (WHILE WET) put on the bulkhead? and then leave it there for 48 hours? OR do i put silicone, scrape it level, and then when dry, put on the builhead?


New member
I put two small beads of silicone on opposite sides on the dry part of the bulkhead that you turn. When you twist it, the silicone spreads evenly.


New member
ok, i see what you are saying.... im worried now ( paranoid really) that two little beads wont be enough.... maybe ill try with 4 beads and twist then....

anyone else agree with this advice?


New member
my bulkheads leaked for the first 3 days i had them, then salt clogged it up. but we're talkign 1 drop of water every few hours.


New member
If you are using silicone, apply it but don't tighten the nuts all the way. Let it dry, than give it a turn to tighten it. That should give you a water tight seal


In Memoriam
If you have to use silicone on the gaskets something is wrong. You should never have to apply anything to a bulkhead to get it to seal. Do you have the gaskets on the flanged or non nut side of the bulkheads and not next to the nuts? How sloppy are the bulkheads in the drilled holes, if they move side to side much there may not be enough sealing surface and you might need different bulkheads? How are you tightening them, they should not be much more than hand tight, any more and you stress them. Are you suspending any piping from the bulkheads and stressing or distorting them. Any pipe should be supported seperately from the bulkhead.


New member
I agree with AZdessertRat,

Never, Ever you silicone on the seals! Its not needed, if you're doing right then all you need is hand tighting with maybe 1/4 turn with a wrench. Anymore than that then you are risking the seal giving in. Also the quality of your bulkhead also speaks volumes. I'm not sure what you Americans use, but we have a really good bulkhead here made by Hayward. Look into quality not silicone.


New member
I agree, no silicone needed! But like azdesertrat said, if the hole is drilled larger than your bulkhead then there isn't much contact surface left for the gasket. Never put the gasket on the same side as the nut or it will leak everytime.


New member
I used the Band-Aid approach, silicone on one of the bulkheads and then tighten once dry. leak test been 10 hours and everything is working.