HOW TO STAY HYDRATED WITHOUT CAUSING HYPONATREMIA

Thanks for getting back to me. We did meet with a nutritionist and have sent yet another email asking this question. My dad's primary care physician was not familiar with the term "free water" and his urologist that performed the surgery said that he does not deal with hyponatremia. I'm wondering if a nephrologist would be the best kind of doctor to help us?
The problem with health care today, especially when going to the ER, is that you get a different doctor and a different nurse, and a different nutritionist every time you go. We get advice from the docs in ER, which they sometimes put in his file, then we have to follow up with someone else.
Anyway - I was mostly looking for experiences people had, not necessarily medical advice.
Thanks agin for responding so quickly.

My dad had his bladder removed back in April. He has an ileal conduit. He is 77. He was not very active prior to surgery; yardwork and working in his wood shop.

About a month after surgery he got a UTI as a result of not drinking enough water. His urine was full of what looked like the swirled egg in egg drop soup. It was impressed upon him to drink more fluid to constantly flush the bacteria from his kidneys (his kidney function is about 46%).
Flash forward another two months and he is rushed to ER with hyponatremia. He was at 118 and apparently we were very lucky because they said anything below 120 can result in a coma. When he was discharged they said no more that 1000mL per day of "free water". We did not understand what this meant. He was drinking about a gallon a day to keep flushing his kidneys and keep his urine light. After ER he dropped it down to just a little more than half a gallon.

After surgery his taste was greatly affected, in fact many things still taste wrong to him. But he especially couldn't stand the taste of water. So he's always used gatorade to flavor the water. He increased the amount of gatorade he mixes with water. However, three weeks later we were back in ER. This time his sodium was at 123. This time the doctor explained that if he takes one of the 32 oz gatorade bottles and fills it with water, that is all the water he can have in one day.

Since then we've been trying to find a balance. Mixing water and gatorade seems to dilute the electrolytes but the gatorade doesn't keep the water from flushing his sodium.
Here are my questions -
1. Has anyone else had this problem?
2. I bought powdered gatorade so we don't have to buy so many gatorade bottles. Would mixing the powder with water count towards his "free water"? We're only allowed 1000mL when mixing water and bottled gatorade so is this the same?

He's afraid all the time that his sodium is going to drop again. I should mention that we use the low sugar version of gatorade because he also has diabetes. We also mix Pedialyte with water.

Any advice would be greatly appreciated. Thanks