high pressure, three-way valve, return lines

[mgebhard]

I just started taking care of a pool and don't have much background knowledge.

Problem: From what I've deduced, there is a three-way valve (see pics) on the return line that sends filtered water back to either a return jet or a side return (with a pressure-driven cleaner attached). When the valve is set to return water through the jet and the pump is on, water flows through the filter at a reasonable pressure and everything looks fine. However, when the valve is set to return water to the side return, the filter pressure is very high and there is much less flow.

History: A few weeks ago, the difference in pressure between the two valve positions wasn't so large, although still evident. When the valve was in the side return position, there was still decent flow and the pressure-driven cleaner was active. Now the pressure is much higher. I've cleaned the cartridge filters a month ago and a week ago so I'm not sure what I could have done wrong there.

Am I misunderstanding what this valve is doing? And what could be causing the high pressure in only one valve position?

 

[ajw22]

Welcome to TFP.

Show us complete pics of all your pool equipment plumbing. The pipes disappear to the left. What do they connect to?

Show us pics of the jet and the side return and your overall pool.

 

[mgebhard]

I've struggled to figure out what's going on because most of the plumbing is buried. In particular, the three-way valve on the return line is connected to three lines that go into the ground. Of those three, I was assuming they are the following: (1) from cartridge filter outlet, (2) to pool side return, (3) to pool jet return.

Here are a bunch of pictures.

 

[mgebhard]

A couple more pics.