Yes Easy, but Water in = water out and the pump runs for as long as the reccomended time, which on the smallest flojets is 4 hours continuos. By restricting the flow thro a smaller pipe or height, that puts some strain on the pump. Flojet and sureflow now have now updated to an integral by pass in the pump for this reason.
Just something you can do if you dont have a built in one for the price of a T and a few plastic Hozelock micro taps.
You could also spend £70ish on a variflow.