Help me understand this plumbing

[orthofish]

I borrowed this pic from rogerbrks. Hope he doesn't mind. I've been trying to understand this plumbing thing for awhile. Ok, the 2 red lines are the pumps? What are the yellow lines? And are the green lines indicating the deck jet lines??? If so, does that mean that each deck jet has its own line??? I thought they would be in a loop.
It looks like there are 2 suction lines coming to the main pump. Is everything to the right (where my green lines are)return lines??
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Thanks[attachment=0:1ssnxige]Pool Plumbing.jpg[/attachment:1ssnxige]

 

[JasonLion]

The yellow arrow on the left looks like it is pointing at a Vac Alert. That is a safety vacuum release system, in case someone gets trapped on the main drain it will disable the pump allowing the person to get free.

The yellow arrow in the middle appears to be pointing at a booster pump, which produces a low volume high pressure flow to power a pressure side cleaner.

The green lines, and the three vertical pipes directly behind them, are all returns of one kind or another. Some will go to normal returns, some to deck jets, some to the spa, and others to any other water features that may be present (I think he has scuppers). Having a separate pipe for every return is not required, but it is more flexible than a loop system. Every return/water feature can be balanced individually using the valves provided.

 

[orthofish]

Thank you. That helps me alot.
What is a scupper??

 

[JasonLion]

A scupper is a mouth or shelf from which water flows. There are some nice pictures of scuppers on this page.