I'm a civilian employee of a SoCal police department and work primarily as an upholsterer. However, part of my duties include cutting the vinyl letters, decals and numbers that are placed on police vehicles to identify them from the air. We print or cut various vinyl decals and signs as well. If you can find a small local business that prints or cuts vinyl letters for signs from adhesive backed vinyl goods, they should be able to cut out the letters/wording to to your specifications (i.e. Size, color, specific wording) to enable you identify your rigid plumbing lines for years to come. (Everything dealing with the police has some kind of vinyl decal affixed to it so everyone knows what to do.) Most vinyls will last 5 - 7 years as long as they are applied correctly. It's the same vinyl used to wrap vehicles with advertising or special designs. If you google vinyl plotters or vinyl cutters, there are even some relatively inexpensive machines to purchase for home use. Software that comes with the plotter allows you to use your laptop or desktop computer select font, size and shape. The adhesive backed vinyl comes in sheets or small rolls in a variety of colors. Hope this helps.