Odd Signs & Symbols

Here's a sign near work which says not to drink the recycled, non-potable water being used for irrigation: Maybe the fact that the water corroded this sign so badly should be a warning of its own.  What's going on here?  Is the water really that potent, or was the sign just made from poor materials? Here's another sign nearby which stays far enough from the water it's warning about:  

Sunlight will slowly damage any paint or materials it shines down upon.  It's not unusual for a bright red paint job to be bleached down to a pale shadow of itself after just a few years.  Here are some otherwise sturdy signs that have been sunblasted and are now just blank or near-blank decorations. It makes me wonder how many years have passed since this thing was checked out by a maintenance crew.  Wouldn't they report that the signs were no longer readable? July 2023 update: fixed it.