I'm trying to open our pool by myself this year. (A decision I increasingly regret.)
Had some issues with the pump, but did get it up and running. Backwashing the filter was fine. But when I turned the handle on the filter to the regular "filter" setting, water began GUSHING out from the heater. (FYI, it's a Hayward H200.)
It's coming out of a small, open ended copper pipe. I've attached a photo so you can see. The problem is: I can't find this pipe on any of the Hayward schematics. I don't know what it's called, what its purpose is, or how to fix it! Seems like it needs a cap on the end or a diverter of some kind, but there's nothing to be seen....