PH ?'s

My ph has just gone up within a few hours. I put some ph down in and brought it down to 5.6 and i checked it a few hours later and its a 6.9. Im growing in a general hydroponics waterfarm. I been using the nute solution for about a week and its just tap water. Should I flush the hydroton and dump the resevoir. Also should I use distilled water or something different besides tap ? Any info appreciated. Also this is my first attempt. THanks

Hydroton should have been washed/rinsed and Ph´ed before using it. Did you use rockwool cubes? They also can create a wide Ph oscilations if not properly Ph´ed. But you have what you have, so I would keep fighting it with Ph´ed tap water, but when you Ph the water make sure it is well mixed, sometimes new hydro growers take a fast Ph reading and the water is not even close to desired 5.8, so at least give your Ph´ed water 15 minutes and re-read your Ph. Once you know your system you will be able to work with it faster. Also some waterfarms have a level hose that can create mold in your rez, pipes, etc, check your whole system, sometimes we can not see mold in it, and mold creates wild Ph problems
Peace, and best of lucks

I'm still a newbie but let me give it a shot. I just started and have had good luck with my PH so i'll just let you know some of the things i do to make sure my stuff is good to go.

--- I have a 20 gallon tank for the specific purpose of distilling my tap water. I usually let the water sit for 24 hours before even introducing it to my drip system.
--- Make sure your nutes are evenly mixed before touching any PH stuff.

If your having PH issues i would definately just clean the whole system completely. Every week i will clean my resivoir with a mild bleach solution. After that i will fill the tank with warm water and run the system a few times (in the bathtub )....I'll even run my airstones in the warm water.

After everything above is done and your still getting PH issues, I would assume (***Again i am a noob still) that the problem is somewhere in your grow medium. i would flush with clean water. And be sure to rinse everything thoroughly , definately dont want traces of bleach in your ladies