Allison,
It is a very individual problem although much more prevalent with us pouchers than the 'normal' public.
It also depends on your body weight, activity level, diet and exercise as well as where you live (hot or cold county) and if you use heat or A/C...all of which are very dehydrating. People also forget that you can sweat more in the cold than the heat!
I had a lot of problems with dehydration as a small kid...I had my colostomy at 2 and it was closed a year later but I suffered from dehydration for over 20yrs afterward until about 10yrs after my k pouch. I used to call it 'my angels'. I would see tiny little dots of light whenever I strained or stood up and always thought that they were my angels looking out for me...funny what kids think!
It is a very common problem for us and we need more than just fluids but mineral salts too...to replenish what we lose over time.
You can try all of the commercial stuff but you may need a made-to-measure solution.
Mine turned out to be homemade lemonade. I squeeze a whole bunch of lemons into a jug of filtered water (limes work well too), add sugar, honey or fake sugar to taste and a couple of pinches of sea-salt or other mineral rich salts. (lately, it has been pink Himalayan salt)...if I want something sweeter I add a tangerine too...I wash them well and throw the rinds into the jug and add a handful of fresh mint leaves...it is very yummy, I keep the jug full at all times in my fridge and top it off with water and ice daily. I make a fresh jug about every other day. You can mix it up with basil or parsley too.
I also drink a lot of herb teas (some are full of certain vitamins and minerals like rosehip (Vit C) or hibiscus (Vit C)).
I am a lazy drinker during the daytime but make sure that I have all of my fluid intake in the morning and at night...so that I only drink a couple of glasses of water at work.
I am a soup person too...all veggie...and homemade...I just steam whatever veggies are laying around in the bottom or the fridge...zucchini, carrot, pumpkin, tomato, onion, garlic, celery, parsley, cilantro...throw whichever into my pressure cooker and then buzz it with an immersion blender strait in the pot...I add sea salt, spices and a squeeze of lemon with a drizzle of olive oil and I am done...perfect winter meal, great re-hydrator and yummy.
If too many veggies give you the runs then throw a potato into the pot to thicken things up.
Sharon