Regular intake of coffee and tea doesn't actually dehydrate you. It's if you abstain from caffeine and then ingest a high dose of caffeine that you start urinating more frequently and therefore dehydrating. If you consume caffeine regularly, you develop a tolerance and you eventually return to a regular rate of going to the bathroom. Tea, being lower in caffeine content in pretty much all of its drinkable forms, you can probably go nuts drinking it and keeping hydrated.
Not that kavalactones and caffeine are the same, but I imagine drinking large quantities of kavalactones would make you urinate more but I'm uncertain if kavalactones cause additional forms of hydration impairment.