double tank wall bulkhead

[karimwassef]

I'm trying to join two tanks with a series of 4 x 4" PVC bulkhead.

One tank is acrylic and the second is glass and wood/epoxy

This means that the bulkhead will join water - tank 1 wall - tank 2 wall - water

in terms of structure, it would be

1. bulkhead face
2. gasket
3. glass 3/4"
4. wood/epoxy 3/4"
5. acrylic 3/4
6. gasket
7. bulkhead nut

I realize that this isn't the intended mechanism, but I'm looking for the shortest interconnect

I considered using two uniseals instead... that feels more robust, but I thought I'd ask first.

[karimwassef]

oh.. the preferred interconnect would actually be a large rectangular opening that can support 6' of pressure and bridge the two tanks...

I gave up on that, but I thought I'd bring it back up in case anyone has a better solution.

[karimwassef]

Any opinions on the three options:

1. Use a single 4" bulkhead across two tanks
2. Use two uniseals
3. A large rectangular interface with a gasket

The third option would look like a flanged acrylic interface with a wide gasket & a series of plastic screws. I know that works at low pressure but this will need to sustain 6' of pressure.

[der_wille_zur_macht]

You want a gasket between the flange face and the tank wall it's sealing against, and then another gasket between the two tanks. You don't need a gasket under the nut inside the second tank.

It should be:

1) bulkhead flange
2) gasket
3) first tank wall
4) gasket
5) second tank wall
6) bulkhead nut

I'm not sure why you're listing three materials if you're only joining two tanks?

[der_wille_zur_macht]

Also, I would trust bulkheads the most when you're looking at 6' of pressure. Flanges seem like a ton of work and pinch points around the screws. Uniseals are great but I don't really think of them as robust enough for something large under a lot of pressure.

[karimwassef]

Thanks.

The glass and wood are part of the same tank. 3/4" plywood/epoxy + 3/4" glass. This is a large back wall: 8' x 30" and will have a total of 16 x 5" diameter holes. That's why I'm backing up the glass with plywood.

I would prefer to cut 6" x 40" slots and connect the two tanks directly.

[karimwassef]

This claims that uniseals are rated to 40psi?

http://archive.reefcentral.com/forum...d.php?t=975360

[der_wille_zur_macht]

40 PSI is a lot more than I expected from a uniseal.

Do the tanks have to remain separate? If you're building one or both, why not just build one big tank instead of two separate tanks that need to be joined? Even if you need two in order to get them in place, maybe build them separate but then glue them together when they're in place? Seems a lot simpler than tons of holes or a slot with a flange and gasket.

[karimwassef]

It's an experimental system and I expect the need to make changes. I would need to separate them without draining the display tank. I was thinking of using knife gates (very thin) between the two uniseals and allowing just enough maneuvering length to push the pipe out of the acrylic side and separate.

The bulkhead option won't work without two separate bulkheads and at least one union.

I hadn't figured out a separation method for a slot

[karimwassef]