this should be a short thread - stupid question

[mojo]

I'm almost embarrassed to ask, but here goes. Since I'm considering buying a tank with a built-in overflow, I've asked several questions about comparing this kind of system to those with HOB overflows. Invariably people recommend getting a tank with a built-in overflow, and they mention to have pre-drilled bulkheads as well ...

...

What's a bulkhead?

Sorry, and hate to ask, but I can't find the answer anywhere.

 

[fishfreek]

A bulkhead is the fitting that goes in the acutal hole drilled into the tank. The bulkhead allows for your plumbing to connect to the hole. The bulkhead will make a water tight seal between the tank and the plumbing.

http://marinedepot.com/aquarium_plumbing_parts_fittings_2.asp#bh

Above are some links to bulkheads.

 

[mojo]

So why do people say to get two bulkheads ... one to drain to the sump, and the other for a return? If that's the case, is a second pump necessary for the powerheads? Sorry that this is aquarium 101 stuff, not very interesting reading anyone except me.

 

[mojo]

By the way fishfreek, thanks for the link ... you da man

 

[ReefRaff]

yes one is a drain and one is the return. the larger hole would be the drain. water is pumped into the tank, and is returned by gravity.

 

[mojo]

If that's the case, with one of the bulkheads draining the tank by gravity, why do you need an overflow chamber? I must be missing a very simple concept.

Is there a diagram anywhere that labels all of the different components of a SW tank? That's one thing I never found in any of the books I've read.

 

[24 hours? NE!]

Look at this thread in the general discussion forum:

http://www.aquariumadvice.com/viewtopic.php?t=22724

It has a picture of what you're asking about- a pre-drilled hole with overflow chamber. You need the chamber so that your whole tank isn't drained (you need a level at which you keep water in your tank).

 

[mojo]

Eureka, that's the missing link ... the holes for the bulkheads are INSIDE the overflow, right? Now I'll sleep tonight, thanks