What is a purge valve and hose, and why does the Guardian Gravity Purifier have one?

The Guardian Gravity Purifier features a purge hose and valve to self-clean the system, no backflushing required. Open the purge valve to flush dirt and air until the water color matches the source water and is free of bubbles. This helps increase the flow rate, because air trapped in the purifier cartridge can reduce water flow. Hold the cartridge horizontally or gently tap the cartridge as water flows to help release the air.
 

Please note, the purge valve releases highly concentrated dirty water from the purifier. Do not allow any drops from the purge hose to splash into your clean water.