What style of bulkhead is better, slip or threaded? whats better for what side of the tank and why?

i like threaded for inside the tank, like for a return nozzle. also, the threads are always undoable.

but threaded fittings often leak. on my overflow i used threaded bulkheads and if there was one thing i could change about my whole build, i would have used slip pvc bulkheads. I have MAJOR salt creep around the threaded fittings, even though i used tons of teflon tape. A correctly glued PVC joint will never ever leak, while threads are hit or miss.

if youre going to use threads, still buy the pvc bulkheads. their threads should fit a pvc fitting's threads more closely. i used ABS and regret saving about $5.

one is not better than the other, just a matter of personal preference.. like sae said, threaded might run into the issue of leaking (which can be solved with plumbers tape) but can easily be removed and reuse. slip on the other hand will no leak, but the bulkhead is pretty much useless after you are done with it.

im a fan of double threaded but depending on how much room you have to play with, slip might be your only choice

TxT always. leaking is never a problem if you take 2 minutes and prepare the bulkhead properly. I have done a bulkhead sticky for several of the forums as seen here:


Bulkhead tips:

1. Always install bulkheads clean and dry, no silicone's, teflons or thread lubricants. Silicone's and lubricants cause the gasket to scoot out or not seal properly. Have you ever removed an old automobile windshield or other gasketed glass? The rubber vulcanizes to the glass with time and creates a perfect seal without any help.

2. Before installing the bulkhead take a few minutes using a jewelers file, nail file or pocket knife and clean any excess flashing off both the male and female threads and from the flat gasket mating surfaces. This is a common source of leaks.

3. Always install the gasket on the flange side of the bulkhead, never on the nut side, regardless if its inside or outside the tank. Installing the gasket next to the nut will lead to leaks. Hand tighten only with maybe 1/4 to 1/2 turn additional, no more.

4. When using threaded bulkheads, again clean the excess flashing from the threads and valleys and use a small amount of teflon tape or better yet the stick or crayon type of thread lubricant designed specifically for PVC treads. These can be found at Lowes, HD, Ace and all hardware stores under names like Laco, Permatex and others.

I use this one and have since the 1980's with great success.
LA-CO: Product Detail - PLASTO-JOINT STIK® - Plastic Thread Sealant
It stays pliable forever and does not tear or roll out of the threads like teflon tape. My swimming pool plumbing up to 2" was all installed with this in 1983, outside in Phoenix AZ and its still pliable to this day!

5. Never support any pumps or piping from a bulkhead, always use supports so weight is not on a bulkhead and gasket causing differential stresses on the mating surfaces.

6. Never screw anything to the external threads of a bulkhead, these are not standard tapered pipe threads and will leak. They are there to screw the nut on is all and are not normally even a standard diameter like 1" etc.

Hope you get some use out of this.