hey guys, when i ph my water, after 24 hours it ra...

Depends on what are you talking about. Do you mean that a glass of water will rise its pH after 24 hours? That is nor normal. If you mean a reservoir (or glass) of feeding solution, varies its pH, then yes it is normal; as the water / nutes concentration varies, the pH will change, which can happen by water evaporating, and the pH will go down as the concentration of nutrients will become stronger, or as the plant takes more nutrients than water, the ph will go up, as water ph is higher than the nutes. To combat this reservoirs have to be big enough so that daily intake of solution is small in comparisson to the overall size of the reservoir. You can also buffer the pH by dumping both pH down and up so the pH is not so easily affected by small changes.