View Full Version : Type of bulkhead (wet side + dry side) - threaded + threaded; threaded + slip or slip

01-18-2014, 05:15 AM
My stand for my 45g cube is finally finished and I'll need to water test my tank for leaks.

There are may choices for bulk heads (wet + dry side) threaded & threaded, threaded & slip and slip & slip.

My cube came with threaded & threaded. On the wet side, I wasn't able to tighten the 3/4" threaded tube into the bulkhead connector. However, I had no problems with the 1" threaded overflows. In fact, I had a couple of rubber O-rings which I installed in between the threaded piece and the bulkhead making it water tight.

I'm worried that the threaded + threaded bulkheads will eventually develop a slow leak over time.

I'm interested in everyone's opinion for the different types.

Thank you!

The Grizz
01-18-2014, 05:22 AM
Did you use any teflon tape?

01-18-2014, 05:27 AM
I did not use teflon tape.

Was I suppose to?

From my understanding, teflon tape is not use with plastic fixtures like this.


01-18-2014, 05:33 AM

You always use Teflon tape for threaded connections.


The Grizz
01-18-2014, 05:33 AM
Using teflon tape will allow the threads to screw together much easier and will in sure they seal.

01-18-2014, 05:36 AM
You shouldn't have to add any o-rings when dealing with pipe threads
This can lead to failures down the road

The 2 best options for connections outside your tank are threaded or slip. This does not include union style connectors
Threaded you use tape, or better is to use liquid teflon (thread sealant). Slip you glue.

Nothing else is needed if it's done properly

Maybe someone living close to you could come by and look over your stuff/give you some help tips etc

01-18-2014, 08:33 AM

Is this the liquid Teflon you're referring to?


01-18-2014, 10:26 AM
As a gasfitter I have some experience with threads, Teflon and dope (liquid thread sealer). One of the first things they teach you in pipe fitting is that Teflon and dope have nothing to do with sealing the pipe, or prevention of leaks. The threads on the pipe and in the fitting ensure the seal. Teflon and dope is used for ease of disassembly. It is a common misconception that Teflon and dope seal the pipe. A pipe, properly threaded, should have 11 threads. After tightening into a fitting there should be 4 threads left exposed.

Also, pipe dope (liquid sealant is an improper name) is made of Graphite dust suspended in a petroleum catalyst. The one in your link has added white colouring.

In retrospect, I would recommend using only white plumbing Teflon on your threads, and proper tightening techniques. You should never have a leak after that. Personally I would use slip with glue and unions. Good luck... and where's the pics?

01-18-2014, 05:50 PM
Well there ya go

That is the stuff I've used. It's messy to work with and gets everywhere
I prefer to use tape myself on anything I need to take apart later but recommended liquid as it's simpler for a layman

01-18-2014, 09:17 PM
I've used teflon tape for plumbing around the house with threads. Its pretty simple and easy to use.

I've used the paste before and its messy.

Thanks for the info. I'll stick with the tape.

Sent from my GT-P5113 using Tapatalk

01-18-2014, 09:24 PM
I wasn't able to tighten the 3/4" threaded tube into the bulkhead connector
Do you mean it wouldn't start threading, or it wouldn't actually tighten up ?

I have my standpipes just hand tight for easy removal and with tape on the threads they are easy to remove if needed. With them installed this way I get no leakage - my overflow box does not drain down when the pump is off

Does that help ?

01-18-2014, 10:54 PM

I've got 2 standpipes in my overflow for my herbie setup which are using 1" MPT to connect to the bulkheads a my return uses 3/4" MPT to connect to the bulkhead.

I have no problems tightening the 1" MPT to the bulkhead. However, the 3/4" is a real pain to get half the threads into the bulkhead. I've gone as far as trying different brands of 3/4" MPT ends.

If I thread it half way, will this be adequate or will it just develop a leak at a later date?


01-19-2014, 01:12 AM
I wrapped 3 layers of Teflon tape onto the 3/4" return and hand tightened into the bulkhead based on the threads in comparison to the 1" herbie drains which I was able to easily hand tighten all the way.

Perhaps I need to try other 3/4" MPT's.

I decided to test anyways by re-installing the 3/4" return into my cube. Needless to say......it's got a slow leak

Any suggestions?? I've tried 2 bulkheads and 2 different brands of 3/4" MPT's......gets very tight after a few turns into the bulkhead even with the use of Teflon tape.

01-19-2014, 01:34 AM
I only use silicone for threaded ABS or PVC bulkheads.
It's a great lubricant which makes for smooth tightening.
I used to use teflon tape but it was a real pain to clean off the threads if I took it apart. Teflon tape didn't allow for smooth tightening. The nut would always "jerk" as it tightened up.
If you've ever used a torque wrench, you know what I'm talking about.
You want a smooth tightening, not a jerky one.
I waited 1 day before filling, but 1 day is nothing in this hobby.
Make sure the rubber gasket on the wet side seats evenly.

01-19-2014, 01:41 AM
Something is not right here. Either your bulkhead threads or your MPT threads are hooped, or are not MPT at all, but you have used two and are seeing the same results. Hmmm. I have 2 suggestions. 1) Teflon goes clockwise around the threads, so as it doesn't unwind as you tighten. 2) You may want to use wrenches to assist in tightening, however go slow and careful not to split female threads. If all else fails get yourself some slip slip bulkheads. Hope this helps.

01-19-2014, 05:55 AM
The threads are not damaged. I took my return and a spare MPT SLIP to JL this morning to test fit. They were all really tight.

Teflon tape is wrapped clockwise, basically in the same direction as tightening the return.

Im shying away from using wrenches to tightening just in case I need to remove for maintenance.

Thanks for the insight.

01-19-2014, 10:04 PM
OK, I figured it out.

The original 3/4" MPT x SLIP were purchased at Home Depot made by Dura USA and NIBCO. I was not able to hand tightening either one of these MPT's into my bulkhead. Once tightened, removing my hand was very difficult without the use of tools.

I went to Rona to with my bulkhead to try the IPEX ones they sell. I was able to hand tighten the IPEX successfully into the bulkhead all the way as well as removing it by hand......no tools.

IMO, the 3/4" MPT x SLIP are out of spec - bad threads.

Thanks for everyone's help!! :smile:

01-20-2014, 12:16 AM
Glad you got that sorted out

Now for my other question;
You mentioned you put an o-ring between the bulkhead and the drain pipe
I'm trying to picture how this is possible
If you threaded the drain pipe into the bulkhead that far for the o-ring to touch you'd probably split the bulkhead

You didn't by chance put the drain pipe on the outside of the bulkhead did you ?

01-20-2014, 05:53 AM
Here's a quick photo of how I was going to use the O-ring by placing it between the bulkhead and the MPT x SLIP.

01-20-2014, 08:00 AM
That o-ring isn't needed

That's your standpipe for a drain correct ?
Just wanted to make sure you're putting the bulkhead gasket inside the overflow and not on the outside of the tank
And the nut goes outside the tank