The Leak-Free Weldless Bulkhead

I personally don't care much for weldless bulkheads in metal vessels but if you HAVE to use a weldless setup, this design is for you. Of course, when you're converting a cooler for use as a MLT, you have no choice but to use weldless. This design is similar to all the kits you'll find online with a couple nit-picky details that I think are absolutely important to keeping it from leaking.




1. 1/2" coupling, 1/2" NPT hose barb (for stainless braid designs), or 1/2" male adapter if using manifold.

2. 3/4" SS washers (meant for use with 3/4" bolts so the ID is close to the 1/2" NPT OD. Use enough washers so that the Oring's inside diameter sits on NON THREADED portion of nipple. The washer touching the oring should be slid all the way down to where the threads end and it should stop there.

3. Silicone ORING AS568A Dash Number 314 3/4" ID.

4. Inside wall of the cooler drilled to 7/8" hole. Note that this hole is best drilled with a holesaw, spade, or forsner bit AFTER the outside hole and insulation is drilled out. This way you won't have to try drilling from the inside of the cooler.

5. Stainless pipe nipple 1/2" NPT (.84" OD actual)

6. short piece of schedule 40 3/4" PVC pipe, just long enough to reach from the inside wall to the outside wall of the cooler. Slit lengthwise with a hacksaw to stretch over 1/2" nipple.

7. Outside wall of cooler (and insulation) drilled out to 1-1/8" so PVC will fit inside. This hole should be drilled first with a holesaw, spade, or forsner bit before drilling the inside wall hole noted in #4. You MUST stop drilling before hitting the inside wall. The center guide of the bit should make a small hole just to guide second bit to keep everything centered.

8. 3/4" washers (meant for use with 3/4" bolts so the ID is close to the 1/2" NPT OD. Use as many washers as necessary to make up for a slightly "too long" nipple. You may have to dremel out the ID to fit over the unthreaded portion of the nipple or use a slightly larger washer. These don't have to be stainless.

9. 1/2" NPT brass Locknut. Can also get away with an electrical conduit nut for very cheap.

10. 1/2" NPT ball valve.


So why is this a superior design? First, having the inside (and only) Oring sitting on the nipple flat doesn't require any huge buildup of teflon tape to keep liquid from getting past the Oring through the threads. Second, the PVC reinforcement holds the inside wall from caving in and ruining the seal. Third, No Orings used on the outside. Any design that suggests trapping liquid inside the wall of the cooler is flawed. Do you want wort soaking into the insulation if the inner seal fails? If you ever smelled a 2 day old mash, you know the answer.