Self Sealing bulk head fittings (http://www.alcohol-injection.com/water-injection-parts-3/self-sealing-bulk-head-274.html)

Drill a 7/8" hole in a flat location and simply place it in and tighten and slide in your 1/4" tubing.

No need for cumbersome bulkhead fittings when you can use DevilsOwn Injections Self Sealing Bulk Head fitting.

Design Features：

* Intergrated 1/4" push to connect fitting
* Buna-N sealing components
* Easy installation
* Suitable for a wide range of liquids

Design Specs：

* Material:Polypropylene,PVDF
* Max.pressure:10bar
* Max.temperature:100℃

http://www.alcohol-injection.com/images/Tank-Tap.jpg