help please with PH flushing

I'm using coco and the PH was around 7 so I started to try and flush them. I'm using distaled water with PH around 4. I've gone though about 6 gals of water but my PH is still at 6.8 which I know is way to high. I can't figure out why it is not going down. I fill the pot up until there is good run off then wait about 20 mins and do it again and again. I do it at least 15 times and the PH won't move. Please tell me what I'm doing wrong. Thanks!

wow, lotsa looks but no replies. Well this is what I did and it seems to be working. I got tired of wasting all the water so I ajusted the water PH to 2 and flushed them with that it went from 6.8 to 6.4 so it seems like I'm on the right track

hey dude i'm about to run a flush today. In coco the first time you flush you have to break a pH barrier. It takes a lot more water your first flush than normal to get it down to your desired level. What you did was kind've right by pHing down at 2. You should mix up your flush feed and pH it to a level (lets say 5. and measure the runoff (lets say it comes out at 6.0) this tells you that your soil is at 6.2. From this you should continually step down to 5.6, then 5.4 and keep readjusting until you reach the level you want. It takes a lot of flushing the first time...this is info that i have been given and its worked for me. Hope all goes well for you...check my grow journal in a couple of days and i'll have updates of after my flushing and the exact amount of water i used. Good luck with your grow!