Plumbing a UV sterilizer

[Fezbearer]

I have a question. When calculating head pressure loss, do I need to just add up the areas in yellow and the three 90° angles?

 

[MnFish1]

I have a question. When calculating head pressure loss, do I need to just add up the areas in yellow and the three 90° angles?

You would also subtract the 'white area' - which is acting by gravity. I do not know how you would calculate the 'resistance' within the UV itself (which should be extremely small) - Since where your pump is - is not shown its hard to answer the question - I would not worry about the intake and outputs.