▁smaller ▁branches ▁reaching ▁out ▁from ▁this ▁' loop '. ▁A ▁gr idd ed ▁system ▁may ▁be ▁imag ined ▁as ▁similar ▁to ▁the ▁lines ▁on ▁a ▁grid ir on ▁football ▁field , ▁where ▁the ▁s idel ines ▁would ▁be ▁ 2 ▁parallel ▁larger ▁' main ' ▁pip es ▁and ▁the ▁yard age ▁lines ▁would ▁be ▁smaller ▁' branch ' ▁lines ▁connecting ▁the ▁two ▁s idel ines . ▁Gr idd ed ▁systems ▁provide ▁multiple ▁paths ▁for ▁the ▁water ▁to ▁travel ▁to ▁any ▁point ▁in ▁the ▁system . ▁This ▁arrangement ▁can ▁be ▁very ▁effective ▁at ▁reducing ▁fr iction - press ure ▁losses ▁in ▁the ▁system . ▁ ▁Most ▁design ▁standards ▁require ▁application ▁of ▁the ▁Haz en - Will iams ▁method ▁for ▁determ ining ▁fr ict ional ▁pressure ▁losses ▁through ▁the ▁pip ing ▁network ▁as ▁water ▁passes ▁through ▁it . ▁Tree ▁and ▁Loop ▁systems ▁are ▁simple ▁enough ▁that ▁the ▁hyd ra ul ic ▁calculations ▁could ▁be ▁performed ▁by ▁hand . ▁Because ▁hyd ra ul ic ▁calculations ▁for ▁gr idd ed ▁systems ▁require ▁an ▁iter ative ▁process ▁to ▁balance ▁the ▁water ▁flow ▁through ▁all ▁possible ▁water ▁paths , ▁these ▁calculations ▁are ▁most ▁often ▁performed ▁by ▁computer ▁software . ▁Today ▁most ▁calculations ▁on ▁all ▁types ▁of ▁pip ing ▁networks ▁are ▁performed ▁by ▁computer ▁software . ▁The ▁sizes ▁of ▁network ▁components ▁can ▁be ▁more ▁readily ▁modified ▁and ▁re calcul ated ▁on ▁a ▁computer ▁than ▁through ▁a ▁manual ▁process . ▁ ▁The ▁ 2 0 1 3 ▁N F PA ▁ 1 3 ▁hand book ▁includes ▁a ▁supp lement ▁that ▁describes