1. The problem statement, all variables and given/known data I have to design a pumping system. Its for a swimming pool. The pool has various fittings (valves, etc) and pipe lengths. My problem is I cannot find an appropriate K value for the filter and sieve. On the suction side of the pump is various valves and a sieve to remove large debris from the pool, similar to this: http://4.bp.blogspot.com/_V5XIbaAr_lE/RyjJCHidz-I/AAAAAAAAAMc/UgHv43xsNRk/s400/sieve.jpg On the discharge side of the pump, the water is pushed through some form of filter. My choice of filter is arbitrary, and so I can choose based on what K values I can find. 2. Relevant equations The head loss for each fitting is K * v^2 / (2g) ( http://www.ajdesigner.com/phpdarcyminorlosses/darcy_minor_losses_equation_head_loss_hl.php ). The K value is normally determined empirically, and then just cited from engineering tables. 3. The attempt at a solution I've tried searching my university library, as well as googling, but I'm unsure of what to look for. I've found K values for the rest of the system's fittings, (Butterfly and Gate valves, entrance and exits, elbows, etc).