I have a D.E. Filter with a Pentair 2" Multiport Valve P/N 261152 .
I've been looking at replacement Sight Glass part information and I'm curious about a particular Sight Glass. The Pentair P/N is 272550 "Sight Glass w/Vacuum Projector".
My original Sight Glass is an OEM "Praher" P/N E-17-S1. Here's the picture:
Here's the picture of the Pentair 272550 Sight Glass:
I'm assuming that the "vacuum projector" is the circled area. What is the vacuum projector? What does it do?