Is there an impact of using a tee in the return piping in calculating head loss. I see the online calculators take elbows and gates into account, but they don't seem to account for tees. Do they not matter in calculating head loss?
A calculator cannot know the orientation of your tee. If there is no flow restriction to both directions through the tee,it will halve your flow. Also any right angle turn through the tee will be close enough to an elbow calculation, whilst not being exact. Allow for any valve restrictions beyond the tee as well.