Adjusting pH in coco coir.

It really depends on how big the plant is. Small plants dont take flushing well, soil tends to hold a lot of water and can over water your plant. You don't even need to flush the whole 10 gal. You can adjust your pH to 6.5 and just start watering regularly with it like normal. It will take a little time but it will bring the pH down to where you want it. If your using sink water let it sit out 24 hours to let the chlorination burn off. Then use your pH adjuster to get it there. Test the water before you start. Always keep the probe wet or moist on your pH meter. Calibration is important if you don't trust it. I calibrated every use, then tried waiting a week. It was off by 0.1 so not to bad.