This will work in principle as an overflow, but I see a couple problems:
You have very little "head pressure" driving the siphon. Your outflow (the T) is 1" or so higher than your tank intake. The siphon will only work when your tank water level is higher than that & it doesn't look like there is much room above to drive the water. A low head pressure equals slow flow & air tend to accumulate & break the siphon. <At 700gph, I have to reduce my siphon cross section area to 1 sq in so the flow is high enough for bubbles not to accumulate .... and the head pressure (water level difference between my overflow boxes) is close to 3". I tried decreasing that by adding a 2nd siphon tube & got air.>
Opaque siphon section means you won't be able to see if you have an established siphon or if air is accumulating.
There were several threads here about DIY pipe overflow (try searching the archive). As I recall the result was mixed. That's why I opted for the traditional 2 box & siphon setup. <you can find one at Dr Froster & Smith for $30 or 40 on sale.>
80 gal FW with 30 gal DIY wet/dry/sump.
9 fancy golds, 1 hillstream loaches, 1 rubber-lip pleco (C. thomasi), 3 SAEs, small school of white cloud minnows, planted.