Where is this water coming from?

[ZWExton]

Refusing to believe I was losing 4"+ of water per week to evaporation, I investigated and discovered that my backwash/pump valve was leaking water into backwash every second the pump was running. I seem to resolved this by taking the big key cover off, rebricaring the seal, and reassembling. I am no longer getting water in the little backwash window (upper right) but when I open the backwash spicket (lower right) I still get free flowing water.

I am a dummy when it comes to pool plumbing. Where is this water coming from? With no water going into that pipe (since there's none passing through the backwash window) how is this happening?

 

[needsajet]

There's a gasket inside the multiport valve called the spider gasket and it looks a bit like a wheel with some spokes. You can see it if you take the top off the valve. The multiport relies on that gasket to send the water in the correct directions. The spider gasket wears out over time and needs to be replaced. Have a look and see if it looks damaged or displaced, pump disabled of course

Here's a video that should be helpful with the explanation: How to Replace a Spider Gasket on a Multiport Valve - INYOPools.com