That's precisely the reason this has never been implemented. It would be too OP.

And balancing it by making it necessary to "purify" new water potions would probably be too much work for a little gain in realism. There'd be inventory clutter due to many empty vials, you'd have to design, program and playtest the new system etc. Almost every single roguelike (and RPGs in general) makes vials vanish after drinking their contents, too, so why not ADOM?

Adom is not every single rougelike. If all other games of this genre lack a certain feature, that does not make it a must or a standard. It simply means their creators failed to find a way to properly balance them.
Most RPGs are simplified because they focus more on other game elements that require significant manpower to program and successfully implement - graphics, physics, voice acting, music, sound in general...

Adom doesn't have those elements so its strength is immersion and complexity. Why on earth is there a feature where you have to eat things that satiate you, you can bless or curse your food, eat corpses that provide multitude of game changing elements, bother with rotting, have an entire character class that has skills related to changing corpses into food rations, food preservation and all the other stuff, but avoid something as simple and obvious as empty vials left after drinking potions, and in case of my RFE - ONLY potions of water? It doesn't make sense.
I'd dare going as far as to say that half the programming and features behind the complex food/eating/starvation system are useless and only help in complicating the game in areas where no complication is needed or justified.
Don't even tell me about adherence to genre because I don't buy it.

Mind you, there would be little inventory clutter since for example b/u/c status would be carried over from the previous status of the potion.
Secondly, considering that random empty vial drop could be set to 20% that of potions of water and you could only refill bottles that you have used up yourself or found, it wouldn't be op, no more than sacrificing 10k gold to raise piety and dropping a heap of 972471 cursed potions of water on an altar to get them all blessed for no cost.

From the lore perspective it would absolutely make sense, definitely more than being able to dip a large object such as a full plate mail, a heap of swords or a pair of boots/gloves and yet only one potion of gain attribute instead of 4 or 10 that would correspond in size to previously mentioned items (not necessarily PoGA but one specific attribute, it wouldn't be too OP).

I didn't mean that ADOM should be like every other RPG, but that I don't agree that adding more realism would make the game more fun. There's far more acceptable breaks from reality in ADOM, including lack of volume restrictions in backpack, other monsters never eating, etc. Yes, roguelikes stand out due to their complexity, but there have to still be limits IMO. (For example, I find the different equipment sizes in ADOM II super annoying.)

This could be implemented in ADOM II, but its' just that I'm skeptical about any big changes to basic gameplay mechanics that have been around so long in ADOM. You'd have to double-check that no new imbalances arise, just to fix a realism issue most people have happily ignored for over a decade.

Hmm, in NetHack you don't just drop water on an altar to bless it, you also have to use a prayer.

The fact this feature is unlikely to be implemented doesn't make it any bad. So I'm voting yes.

Now that you mention it, if you throw a 'Fluff Ball' into the red lake, well nothing happens. Quite dissapointingly so, I was hoping for some action. :P

Potion flasks aren't reusable for the same reason amulets of life saving are destroyed after they save your life.

I won't even comment on comparing potions of water to AoLS, it's laughable.
If you can't see the difference here then you probably shouldn't take part in this discussion.

There is a lot of nice suggestions in the starting post. But I voted against it. I think the level of complexity/item interaction will become too high. Imbalance can arise quite easily while the potential gains are just marginal.

Not everything has to be realistic to be realistic. In ADOM, potions obviously are a single unity. There is no flask and liquid. There's only a potion. If there were flasks and liquids, one would have encountered them randomly in dungeons. Or one would be able to wish for them. When you drink the potion, it is gone. When you smash it, it's gone too. There are no shards, no bottles, nothing at all. It's not unrealistic. It's a potion.

The idea is the same. They're meant to be one-use items. Flasks that can be emptied to be turned into potions of water would be too useful.

I do think it's silly not being able to flush your heap of 15 potions of stun recovery and fill them with water from a river, but it's like that for a reason.

I dislike the idea of having all potion vials left behind after using the potions.

But I do like the idea of introducing empty vials. Such vials could have multiple uses. The obvious one would be filling at a river or water trap, resulting in a plain old potion of water... but you could also use it on a regular pool to get a semi-random potion (but it would immediately use up the pool), or the pool of the Stone Circle to get potion of raw chaos (this pool would not be used up by this act, allowing you to create more potions of raw chaos from empty vials on demand). For a bit of variation, perhaps using an empty vial while Sick could be a method of obtaining a Potion of Sickness. And maybe giving an empty vial to a certain NPC (I'm thinking Jharod) could allow you to obtain a potion of healing.

Perhaps there could also be a method of emptying a potion vial using a potion of water (in addition to the vial being emptied - yes, even if you're emptying a potion of water, so to empty a potion of water, you need to use up two potions of water). That way, you can't abuse it to obtain additional potions of water (because one is used up to create an empty vial).

my thoughts on the topic. Also, instead getting a semi-random potion from a normal pool and draining it instantly, the vial should turn into a !oWonder with the normal chance of pool disappearing as usual. I think the random way it works would be a good enough representation of how pools work :)

What if potions only leave empty vials, like, 20% of the time? That would not allow any abuse.

Even 20% would still produce a *lot* of vials, and lead to an overabundance of holy water if they could be refilled.

Too much holy water is bad for the game as it removes cursing as an obstacle and vastly increases the power of all potions and scrolls. At the moment you have to make careful choices of how to use your holy water, with water itself being hard enough to find early game. This is as it should be - it's a resource that you have to think about how to apply. With refillable vials you have nigh infinite water from the moment you find a river, and as much holy water as you need as soon as you find an altar. Way way too unbalancing... And all for what? A touch of realism? Corpses don't leave bones, iron rations don't leave weighty packaging, scrolls vanish when read, you can eat/drink without pooing or peeing (fertiliser to improve herb growth anyone?) and many monsters leave nary an ounce of flesh when killed. In the interests of balance and keeping junk items low I'm all for a little unrealism in ADOM.

Infinite access to potions of water would also mean infinite access to potions of raw chaos, with Moon Sickle. You could then dip your infinite potions of water into these infinite potions of raw chaos, which, if my understanding is correct, can be done without risk of explosion if dipped in Terinyo (which has a handy source of water too). This would then give you an infinite supply of potions appropriate for that level, which I believe would include potions of booze. Your infinite supply of booze could then be used to give all wands an infinite number of charges. Or since you're in Terinyo, how about giving them to Yggaz? And so on and so forth. Infinitely reusable items are trouble.

As ADOM inventories didn't have enough clutter as it is.

I think either I misspoke or you misread.

My initial post later states that it would perhaps be a better idea if ONLY potions of water produced empty vials. This pretty much reduces the amount of vials to how many potions of water you already used.
Additionally if the drop rate for vials was 10-20% of current PoW drop rate PLUS refilling would only be successful 10-20% of the time, that gives you a pretty low chance to make a potion of water, but still higher than zero.
You can't just empty 15 potions of whatever and fill them with water. You need to use potions of water in the first place.

As for addressing comparison of potions of water with AoLS:

AoLS is an extremely rare item that many people would wish for. It has a very powerful effect, while potion of water is a semi-abundant item that has limited effect on overall gameplay in small numbers (which would remain small even if the feature I suggested was implemented) hence comparing the two is completely pointless.

Again, no other potions BUT potions of water would produce vials, thus the balance of items remains.
People saying that inventory is already cluttered should perhaps post an RFE that would suggest removing several items or types of items that are completely useless.
That would certainly bring a bit more clarity to PC inventory.

AoLS are extremely rare, but the main reason people would wish for them is that Khelly needs one. On its own, it's got some flaws that lower its usefulness. They can be burned, rusted away, destroyed or cursed, and they only save your life once, and whatever killed you the first time is likely still around. There are much better uses for wishes.

The potion of water has a great effect on overall gameplay even if you only have a couple of them simply because many items become much more powerful and useful when they're blessed. If you only have a couple of them, you end up having to figure out which items need the blessings the most, turning the use of holy water into a meaningful choice (having meaningful choices is what makes a game a game, as I think Sid Meier has pointed out). If you introduce more water, you rob the choice of meaning, since you can bless everything that needs it, and eventually everything.

If your argument is that it's more realistic to be able to reuse potion vials, it doesn't make sense to restrict it to water. That might be the source of the misunderstanding. In any case, this RFE requires a considerable amount of effort for no discernable beneficial effect on gameplay. Or, in shorter terms, it's a waste of time.

This is a bad idea. It would require a lot of rebalancing for potions of water, which currently work out pretty good on the whole--not so many that you can waste them, but you get enough to bless the important things, usually (at least, by the end of the game). There's nothing this accomplishes except adding tediousness to the game.

Empty vials as a separate, non-reusable tool that's randomly found and generated [like torches] bringing some more use to rivers and pools... a man can wish

Sorry, I really don't see the point in this. By the time you take balance into consideration you've done a lot of work for little benefit.