I think it's a combination of older people often needing to drink more (or remember to drink) coupled with the bladder problem being such a nuisance that at some mental level, he 'forget' to drink in order to have less of an incontinence problem.
mother in law has bladder dysfunction issues. So do I to a certain extent (OK, too much information, sorry) and I have been out in public with mother in law and seen her refuse to drink even when she's thirsty, because she is afraid of "not making it" inside in time when we get back home. I remember my mother when on "fluid tablets" and how she had to plan her trips around the availability of public toilets at the time she expected to need them. But my mother was very medication-compliant. In an older person who is behaving like a spoilt brat, who is being wilful and getting stroppy about all the medications, it can be a huge headache. I've learnt with mother in law, to organise "pit stops" because she WON'T tell me she's needing a toilet, not as much as she should.
Your body needs a lot more water than we generally put into it. When we're older, our bodies can be less efficient at how kidneys work, or the liver. More water makes it easier for it all to work better. The GI tract also needs enough water to bulk out the fibre and to hasten things on their way.
Does your dad wear incontinence pads or pants? I think there are also bags guys can get, which stick on around their very convenient appendage. If his problem is an overflow or lack of warning, just a bit of leakage, then he won't need as much "mopping up" gear as he would if the problem is simply the whole lot letting go suddenly; whatever you use has to cope not only with the total volume, but often the flow rate too. Technology these days is good though.
Dehydration can led to mental confusion, as can salt imbalance, but if he's got congestive heart failure problems and especially if his oxygen sats are not as good as they should be, that will be having an effect also.
With his medications, would he use a daily pill container system? I can think of three options:
1) I don't know if you have this in the US, but here in Australia, our pharmacists can make up a patient's medications into a customised sealed pill pack. It takes all the worry out of having to do it yourself, especially when you're on a complicated regime.
2) The daily pill container. This may need to be a more complicated one, because someone on a lot of medications, especially given over a larger number of different times of the day, needs to have this organised well. You might need to set up a baggie system in association with a daily dose container. Or alternatively, multiple daily dose containers, all taped together, but different colours so the pills needed to be taken without food, for example, are in one colour; pills needed to be taken WITH food are in another colour. The advantage of both these options is that someone can double-check if medications have been taken.
3) A set of reminders on the computer or an alarm clock or even alarms set on the mobile phone. Carrying spare sets of medications (your mother or whoever he's likely to be out with) can make it easier to make sure he doesn't miss doses. When you get him home, you immediately replace any spare sets of medications, from the relevant dose compartment. It re-stocks the spare set and also prevents accidental multi-dosing.
You can also use combinations of all these.
My mother also had congestive heart failure, along with a lot of other health problems. I remember she had congestive heart failure for about 20 years before she died. She had a multi-dose pill pack "daily pill container", the first time I'd ever seen them. Hers was a block of 7 separate packs, each with 4 compartments for "Morning", "Lunch", "Dinner", "Supper". She could remove a daily pack if she was going out for the day. For her, it was a good system. But she was unable to make up her pills by herself. While he was alive, my dad made the pack up. Afterwards, my eldest sister did the job. To assist, there was a chart that Dad had made up, which was stuck to the fridge. I strongly recommend a chart like this for whoever is making up your father's medications. And if he is showing signs of confusion, it shouldn't be him doing this unsupervised.
Maybe if your mother could make up a chart like this for your father, he might find it easier to do this for himself. Down the left side you list the medications. Across the top you put the times of day that pills are to be taken. To get this right, you need to allow spaces for the full span of times needed. For pills to be taken "as needed", they may need to be allotted a daily maximum in a separate labelled container, so he doesn't accidentally overdose.
You then go through each pill and, according to the prescription, you mark off with a tick when it is to be taken. This can take some time to get it right but it is worth the effort. Once you've done one, it is easy to change if a different pill is prescribed. Obviously if a pill is dropped, it's just a matter of ruling out a line.
Next - go down the RIGHT side and for each line, tally off the ticks so you have a single number, the total number of those pills per day. This to help with the daily organiser but it also can help with the stocktake of pills, so you know when to go get refills.
For the daily organiser making up, you need a container system that has the same number of compartments as dose times. So if pills are to be taken on six different times in the day, you need six different daily compartments. You can do this with a double system of three compartments per day; just stick different time labels on the compartments.
Older people and chronically ill people can have very complex medications, and too often the medications' complexity and multiplicity can also add to a health crisis. A lot of medications add to the risk of unnecessary medications still being taken after the doctor thinks they have been discontinued. In a situation like your father's, especially if there's any mental confusion, a doctor can say, "OK, we have a new medication which I think will be a better fit for you; stop taking medication a and take this new medication B instead."
Patient gets home having had new prescription filled, but also having collected a batch of repeats from the pharmacy as well. Or if he uses multiple pharmacies, the whole list may not be properly supervised. It is too easy for someone to keep taking medication A as well as medication B, thereby doubling up on something that could make them sicker.
That chart I described - every so often Dad would take tat chart to the doctor with Mum and the doctor would go over the chart. Sometimes, too often, the doctor would say, "Hang on; I though I discontinued tat one two months ago," and things would be remedied.
These days in Australia, computer files at both the doctor and the pharmacy keep track of these sort of issues, as well as being programmed to alert the operator to any drug interaction or contraindication. My file, for example, lights up red with all my allergies and if a doctor is about to prescribe a new medication which has any ingredient in it (even the colouring) which could trigger a known allergy, the program alerts the doctor or the chemist.
Still, nothing beats your own method of cross-checking safely.
I realise I'm probably offering way too much help here for someone who provably isn't interested in help nor prepared to accept it, but whatever happens from here, it will be easier on you and your mother, if you both know you have done everything you could, to alleviate your own sense of responsibility.
Marg