[LWC Ltd]

Im trying to sort out a di only system and after reading up on posts etc decided to have the tank full of tap water and push it through the DI's

I have an inline 2 point tds metre which squeezes the water tight at those points, then there's 100m of microbore. 

It seems to create a lot of back pressure. Could it be air getting in system or is it the narrow and lengthy hose thats causing all the back pressure?

Seems to spring leaks due to the pressure. Any suggestions please?