Calling all plumbing experts!


New member
Hey guys,

I am in the process of setting up a new tank and I had a question regarding gaskets for plumbing the tank. This one is a bit unusual, so I couldn't find any info on this particular topic already.

I purchased a glass-holes overflow for my tank. If you are not familiar with their system, the box is held in place by a bulkhead which tightens the box to the glass of the tank. On the inside and outside of the tank, there is a bulkhead gasket to create a watertight seal. Here is the picture from the instructions.


Because of the installation, the overflow box is away from the glass for the thickness of the gasket. In my particular situation I plan to use my light mounting right where the overflow is, like so.


Because of the gap, if I were to tighten the light clamp, it would squeeze the top of the overflow to the tank and cause stress on the glass/box, potentially causing cracks. My idea was to get another gasket the same width and put a piece of rubber on top to keep that from happening. While I was at the store, I ran into a kit to make your own gasket. I was able to make one the size of the entire overflow. Here is the picture, with the orange being the new gasket that's on the inside of the tank.


Here are my thoughts about the advantages of this:
1. No small gap for debris and other stuff to get stuck behind the overflow.
2. I can put my light clamp without causing stress on it.
3. It looks like it would sit more evenly and cause a better seal.

Number 3 is the one I'm not sure about. Would it actually cause a better seal? Or would it not work because the pressure would be distributed more evenly through the entire gasket, making less of it, and in fact applying less pressure which wouldn't make as tight of a seal?

Any tips or advice would be helpful who knows about this. Thanks in advance, and sorry for the long post.


Active member
I won't swear to it, but that seems like a fine idea to me. Please let us know how it works!

(After the lengthy leak test outside)


New member
After I'm done making everything, I plan to do a 3 day fresh water leak test. I'll probably sit it in the garage and see how it does.


New member
This is a goid idea and should work totally fine. Just make sure no to over-tighten the bulkhead nut. Over-tightening the nut could cause it to deform in the center and you could lose some of the sealing capability. I use something very similar to these at work for industrial baking equipment and they work really well.

Good luck


New member
If you install a bulkhead like they want you to (backwards) then you don't need that gasket between the box and the glass on the inside. The only gasket necessary is the one between the flange and the glass.

Installed the other way (which is impossible with the box size) you would need 2 gaskets, between the flange and the box inside, box outside and glass.


New member
What you have done looks like it should work fine. If you want to be extra sure, I have seen people put a bead of silicone around the outside flange. Test and see, that is the surefire way to know.