View Full Version : 340 gallon build bulkhead question

07/08/2017, 11:07 AM
So I recently ordered a 340 gal tank from miracles. I intended to have 3/4 inch return bulk heads in the rear. Unfortunately the hole size is 38 mm. I planned on using schedule 80 bulkheads. They don't fit, in a couple mm off. My alternatives would be 1/2 inch schedule 80 bulkheads (which will fit but will have limited coverage for the o-ring) or 3/4 inch ABS bulkheads. Anyone have any thoughts? The return holes are only a few inches from the top so I would imagine a 3/4 abs bulkhead would be good. I have bought all my plumbing already so would prefer to avoid using reducers and everything to go from 1/2 inch to 3/4, it would also require a large order return to size down.

Any thoughts? Does it make a difference?

As a note the hole size issue is on me. I never specified I intended to use schedule 80 bulk heads just that I wanted 3/4 bulk heads.

07/08/2017, 05:46 PM
I would try to use the 3/4 bulkheads if possible on this size tank, you could be cutting off almost half the flow by going from 3/4" to 1/2".

You could get Spears bulkeads and sand a bit of the threads off carefully so they will fit the holes. I have done this with a lathe in the past and the results were better than expected. Since the threads on the Spears bulkheads are so beefy they ended up being much stronger than the ABS bulkheads despite the removal of material. And it's likely that the drilled holes will be close to 40mm if you measure with a caliper so you probably won't need to remove much of the thread.

Just get one bulkhead so, worst case, if you modify the Spears bulkhead and you're not happy with the results you can just go ahead with another alternative.

07/08/2017, 08:12 PM
I appreciate the suggestion. However, I am entirely inept at making or altering things and having them come out in good shape. Moreover, I am not entirely sure I know what a lathe is nor how to operate one. So to learn something new and use it as the primary means to keep 30 to 40 gallons of water in my tank seems a daunting task.

I was, however, also feeling that sticking with the 3/4 abs would be better. The flow is better, the holes are located near the top so there isn't too much pressure, and they are a more snug fit for the holes in the tank.

07/08/2017, 08:13 PM
Also if I go with 1/2" I have to either add conversion pieces or return and exchange all my NPT tubing and nozzle outlets.

07/08/2017, 08:44 PM
go with abs.
if your back wall is black and use locline inside the tank that fits right in with color.

07/09/2017, 04:21 PM
The Sch40 bulkheads will be just fine - Sch80 are mostly unnecessary anyhow. You definitely don't want to go down to 1/2', not on a tank that large.