Clean up water purification

[kevingranade]

For something that's pretty central to survival, water purification is quite haphazard.

Some cleanups we can do:

1. Differentiate between clear (but possibly contaminated), cloudy (obviously dirty), and tainted (from a very dangerous source) water.
2. Differentiate between biological and chemical contamination. (internally, this will not be player-visible without a test)
3. Carry contamination across recipes as called for.
4. Differentiate between sterilized (boiled/chemically treated, not that tasty) and filtered/distilled water (very clean).

To be more concrete, I'm proposing:
New Items:
cloudy water (obviously dirty, probably unsafe, from rivers)
toxic water (obviously dirty water from an obviously dangerous source)
sterilized water (flat or chemical-tasting water, biologically safe, output of boiling or chemical purification, lower morale boost than clean water)
water test kit (item used to detect chemical contamination in water)
New item attributes:
bio_contamination
chem_contamination
Code changes:
Enhancing recipe code to copy contamination from inputs to output
Enhance recipes to indicate whether they transfer contamination
Item changes:
Let iodine be used to sterilize (percent chance?) water.

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[KA101]

If water from the same source (river/lake/etc) retains the same cleanliness, etc when I get more of it later, then yeah, this sounds interesting. Nontrivial chance for tedium though, I'm thinking?

[illi-kun]

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[MrHrulgin]

Here's my take on water and its sources:

1. Terrain: Fresh shallow and deep water in flowing and still versions, shallow and deep salt water as well as pool water and sewage.
   a. Still water would be clear by default. Unless there's a current to keep it moving solid particles would drop to the bottom and even sewage would settle out within a few days of the sewer system ceasing to function. This would have no effect on its potability.
   b. Flowing water would be cloudy, but not inherently any more unsafe than still water in the region. How to model that variation in potability effectively is an open question, discussed below.
2. Water from pre-cataclysm municipal sources (currently hot water heaters and toilets). Clean and clear, though potentially dropping in safety over time if water contamination is modeled.
3. Water from wells, shallow and deep. Presumably water heaters and toilets in more remote houses and locations would also be from local wells. Of variable safety depending on local groundwater.
4. Water that is visibly off or definitely tainted. Pools of water in gutters with a sheen of oil, toilet tanks with brightly colored toilet bowl cleaner pucks, water from swimming pools etc. Possibly water flowing from pipes like you can see at homeless encampments. This water would not be made potable by boiling, as these contaminants wouldn't be neutralized by heat. Possibly a more advanced water filtration system would be able to deal with this stuff.

Questions:

1. How to test water safety? Many minerals or pollutants will change the water quality in ways that are easily noticed ( taste, color, odor and staining of fixtures). This can affect all of the types of terrain as well as wells, and should be very visible to the player once they're looking at it. Some of this water, while having alarming characteristics, is still safe to drink. (Or, in extremis, having deleterious health effects that are much longer-term than dehydration.) I haven't found anything online that shows how to make your own kits that test for potability, so they're single use and pretty irreplaceable?
2. How to model water safety? Water flows the entire length of the Mississippi in 90 days, so within a few months pollution from industrial sources would have gone into the ocean or terminal lake, but in that same timeframe you'd see new issues from lack of maintenance on those same industrial systems. Is it possible to affect groundwater quality based on distance from special locations? The groundwater will be worse next to a dairy farm than it will far away from human construction. Presumably there would be a groundwater safety quality and a flowing water safety quality, and the sum of the two is how dangerous the rivers are to drink? There's some work being done on lakes and rivers; possibly model groundwater boundaries based on that system? Depending on the complexity of the groundwater modeling, there could be significant amounts of useful trace minerals in the water.
3. Longer term water storage: should water in unsealed containers become contaminated? Water in toilet tanks and water heaters that might be good in the first few weeks may not be good indefinitely, and water that's boiled and poured into an open tin can on the counter will not stay good for long. This opens up possibilities for preserving water sources much like other foods are preserved. You shouldn't expect to boil 60L of water, leave it sitting by your stove and then come back in a month and find it fine.

I agree with the types of water laid out by Kevin. There's been recent upgrades to recipes to track calories from the base ingredients and will carry the (rotten) effect across; will that system work for water contamination? (See here) Will the types of contamination have different effects? Requiring different purification types? I don't know if there were as many options for water purification when Kevin proposed this. As it stands, boiling, the water purification tablets, charcoal water filter and the electronic water filter all would deal with biological contaminants, but only a distillation system like a still or a solar distiller would consistently separate the chemical contaminants from polluted water. Some chemicals have a lower boiling point than water, so even those wouldn't be removed IRL, but we might handwave that issue.

[kevingranade]

This issue has been mentioned on Cataclysm: Dark Days Ahead. There might be relevant details there:

https://discourse.cataclysmdda.org/t/why-are-swamps-in-this-game-filled-with-salt-water/25349/6

[I-am-Erk]

There's really no reason not to implement this now, it should be pretty trivial (to start on the framework, at least)

[I-am-Erk]

I was requested to add some implementation details here, so here are some general thoughts. Let me know here or on discord if you're interested and want more implementation talk.

• water could use the item fault system to track purity.
• there are three major contamination types for water that we could track. Two are fundamental, one is hard. The fundamental ones are "particulate" and "biological", the tricky one is "soluble".
• particulate contaminants make it hard to clear biological contaminants. Particulate can be removed through several forms of filtration. Filtered water is safer but still not safe.
• once particulates are filtered the biological contaminants can be removed in many ways such as boiling, UV exposure, chemical cleaners.
• soluble contaminants are generally rare and represent things like chemicals in the water, or salt, or other stuff that isn't removed by filtration and boiling. We have two options here, we could just call this water unsalvageable or we could make it possible to distill it to get pure water. I think allowing distillation to purify it ultimately is a pretty decent option but worth noting it requires a bit more knowledge than one might expect... You do need to make sure that you know what to keep and what to discard.

[nornagon]

Thinking through some more technical/implementation details.

• Currently the way to repair an item fault is to select (m)end on the item, which seems like a sort of strange verb for purifying water. The crafting system seems like a more natural fit here, perhaps?
• Breaking contamination down into particulate, biological and chemical makes sense. That's roughly how the EPA breaks it down, too (they add "radiological" as a fourth category). In theory, water with only particulate contamination would be safe (but unpleasant) to consume, but it's unlikely that a survivor will encounter particulate-contaminated water that isn't also biologically contaminated, so probably not worth modeling.
• Modeling increasing biological contamination over time for clean or sterilized water in unsealed containers seems reasonable to me. This is essentially similar to food going rotten.

flowchart LR
cloudy_water -->|filter| water -->|sterilize| sterilized_water -->|distill| clean_water
sterilized_water -->|time unsealed| water
clean_water -->|time unsealed| water
water -->|distill| clean_water

Loading

• Water in lakes, rivers and in puddles would become cloudy_water. Water in toilet tanks would become clean_water (degrading to water over the course of a few weeks). Water in water heaters and such is already clean water; additionally, those containers are SEALED so the water in them would stay clean indefinitely.
• I don't think it's reasonable for a survivor to be able to remove arbitrary soluble contaminants from water. Further, I think this case is rare enough to not worry about terribly much—there are many better sources of water, a survivor doesn't need to resort to complicated sewer-water distilling mechanisms. We have mutations if you want to roleplay a sewer rat.

I think it's reasonable to assume a survivor would have a pretty good idea of what water is how safe to drink. Drinking from a river, or puddle in the dirt? Probably not great. Drinking from a toilet tank? ehhh if it's been a few months it'll probably look pretty yucky. So I don't think it's worth trying to hide the particulate/biological contaminant status of water from the player behind a test kit—especially as such test kits are not reasonably craftable by a survivor, so they'd be a consumable resource. I could see it being interesting/fun to have certain chemical contaminants be undetectable without a test kit, e.g. radiological or other contaminants leached from a toxic waste dump, perhaps with the possibility of causing mutations if you drink too much?

[Edited to add a line from water --> clean_water via distillation without sterilization, as distillation also removes contaminants.]

[nornagon]

I've been looking through the current system for water contamination, wanted to note down what's currently there to capture existing thought. Whether or not we want to preserve any of this behavior, we should at least know what we're replacing :)

How does water become contaminated?

The definition for water doesn't include anything pertaining to contamination, so how does it become contaminated?

• water sometimes has poison in it, depending on where it spawns. This is set on the item at spawn time in map code.
• SPAWN_WITH_LIQUID + FRESH_WATER on a terrain spawns it with some water. This is only used for t_puddle and t_puddle_underground currently, which both also have the MURKY flag, which causes the water to have poison = rng(1,6), as well as parasites = 5 and contamination = { { disease_bad_food, 5 } }.

  Cataclysm-DDA/src/map.cpp

  Lines 2247 to 2257 in 9eaa5d4

  	if( new_t.has_flag( "SPAWN_WITH_LIQUID" ) ) {
  	if( new_t.has_flag( "FRESH_WATER" ) ) {
  	item water( "water", calendar::start_of_cataclysm );
  	// TODO: Move all numeric values to json
  	water.charges = rng( 40, 240 );
  	if( new_t.has_flag( ter_furn_flag::TFLAG_MURKY ) ) {
  	water.poison = rng( 1, 6 );
  	water.get_comestible()->parasites = 5;
  	water.get_comestible()->contamination = { { disease_bad_food, 5 } };
  	}
  	add_item( p, water );

• Water from water-source terrain ("examine_action": "water_source") with the MURKY flag gets the same treatment—poison = 1..6, parasites = 5, and 5% contamination with food poisoning.

  Cataclysm-DDA/src/map.cpp

  Lines 5308 to 5316 in 9eaa5d4

  	if( has_flag( ter_furn_flag::TFLAG_MURKY, p ) ) {
  	for( item &ret : get_map().i_at( p ) ) {
  	if( ret.made_of( phase_id::LIQUID ) ) {
  	ret.set_item_temperature( std::max( weather.get_temperature( p ),
  	temperatures::cold ) );
  	ret.poison = rng( 1, 6 );
  	ret.get_comestible()->parasites = 5;
  	ret.get_comestible()->contamination = { { disease_bad_food, 5 } };
  	return ret;

• Water from water-source terrain with the TOILET_WATER flag is clean 1/3 of the time, otherwise has poison = rng(1,3).

  Cataclysm-DDA/src/map.cpp

  Lines 5321 to 5327 in 9eaa5d4

  	if( has_flag( ter_furn_flag::TFLAG_TOILET_WATER, p ) ) {
  	for( item &ret : get_map().i_at( p ) ) {
  	if( ret.made_of( phase_id::LIQUID ) ) {
  	ret.set_item_temperature( std::max( weather.get_temperature( p ),
  	temperatures::cold ) );
  	ret.poison = one_in( 3 ) ? 0 : rng( 1, 3 );
  	return ret;

• Water from other water-source terrain will have a varying chance of poison from 1/3 to 1/20 depending on the DEEP_WATER and CURRENT flags.

  Cataclysm-DDA/src/map.cpp

  Lines 5345 to 5363 in 9eaa5d4

  	if( terrain_id->has_examine( iexamine::water_source ) ) {
  	int poison_chance = 0;
  	if( terrain_id.obj().has_flag( ter_furn_flag::TFLAG_DEEP_WATER ) ) {
  	if( terrain_id.obj().has_flag( ter_furn_flag::TFLAG_CURRENT ) ) {
  	poison_chance = 20;
  	} else {
  	poison_chance = 4;
  	}
  	} else {
  	if( terrain_id.obj().has_flag( ter_furn_flag::TFLAG_CURRENT ) ) {
  	poison_chance = 10;
  	} else {
  	poison_chance = 3;
  	}
  	}
  	if( one_in( poison_chance ) ) {
  	ret.poison = rng( 1, 4 );
  	}
  	return ret;

• Water from rain has a 1/10 chance of being poisoned per, uh, attempt? I think this chance might currently differ depending on whether the funnel is in the reality bubble or not.

  Cataclysm-DDA/src/weather.cpp

  Lines 246 to 250 in 9eaa5d4

  	if( contents.can_contain( ret ).success() ) {
  	// This is easy. Just add 1 charge of the rain liquid to the container.
  	// Funnels aren't always clean enough for water. // TODO: disinfectant squeegie->funnel
  	ret.poison = one_in( 10 ) ? 1 : 0;
  	put_in( ret, pocket_type::CONTAINER );

What are the effects of poison?

• Consuming water with poison > 0 will give you food poisoning for (poison * 30) mins, and if the poison is above rng(2,4), you'll be extra poisoned for (poison * 10) mins. Unless you're an Eater Of The Dead.

  Cataclysm-DDA/src/consumption.cpp

  Lines 1099 to 1107 in 9eaa5d4

  	// If it's poisonous... poison us.
  	// TODO: Move this to a flag
  	if( food.poison > 0 &&
  	!you.has_trait( trait_EATDEAD ) ) {
  	if( food.poison >= rng( 2, 4 ) ) {
  	you.add_effect( effect_poison, food.poison * 10_minutes );
  	}
  	you.add_effect( effect_foodpoison, food.poison * 30_minutes );

• Crafting anything with poisoned water removes the poison. This is a bug; only recipes which heat the water should remove poison.
• Combining water with differing poison levels (e.g. by Unloading) will result in the poison level of one being overwritten by the other, depending on which one is being poured in. This is a bug.
• Finally, NPCs won't accept poisoned food from the player, so this can be used as a water test kit. Also seems like a bug :)

  Cataclysm-DDA/src/npc.cpp

  Line 3233 in 9eaa5d4

  if( it.get_comestible_fun() < 0 || it.poison > 0 ) {

[nornagon]

My feeling on the existing system is that it is fairly incoherent and doesn't provide that much interesting play. Water from different sources will have different likelihoods of poisoning you, but in a quite opaque-to-the-player way. It's fairly easy to purify water for drinking, so most players group all unclean water together as "not safe to drink" regardless of its source, which flattens all the mechanics described above about source location.

I propose we actually flatten the mechanics and make the different contamination levels more visible to the player.

• water should become "safe-ish" to drink. This is water from rivers/lakes, or water that's been standing in a container but unsealed for a while. The water is visually clean, but obviously not sterile, based on its source. The main danger here is water-borne disease such as cryptosporidium, giardia, or E. coli, which generally come from contamination with animal feces. I couldn't find a good estimate of how likely you are to get one of these diseases from drinking e.g. water from a river. But we can make something up and tweak it until it feels right. Something in the range of 0.1% to 1% chance per unit of water consumed seems about right to me. Let's flatten out the specifics of whether the water came from a river, or from deep water, or from rain, into a flat, low probability. This seems about the same as carefully tracking the source, from a gameplay perspective—if you're okay risking illness, you can drink river water; if you want to be safe, purify it first.
• Instead of immediately giving you food poisoning/poisoning, model something closer to cryptosporidiosis/giardiosis/gastroenteritis, where it takes a little while after consuming the contaminant to experiencing symptoms.
• Add water_murky, which is e.g. puddle water or swamp water. This is obviously contaminated, full of particulate matter and/or algae. I'd say this water shouldn't even be drinkable, or if it is it's guaranteed to make you sick. But it can be filtered (via a variety of methods) to become water.
  • Filtering techniques should include using a commercial filter (e.g. LifeStraw, tablets, etc. which can go directly from water_murky -> water_sterilized), using an improvised filter using e.g. sand, charcoal, coffee filters (which would go from water_murky -> water, after which it could be boiled to get water_sterilized).
• Add water_sterilized, which is identical to water_clean in everything but morale. It doesn't taste as good.
• water_clean and water_sterilized degrade to water over time, unless in a sealed container.
• Non-boiling recipes should carry over contaminant risk if they're made with water instead of water_clean.

I think this is a bit of a different vision from what others proposed in that there's less hidden information about contaminants, rather than more. But I think this system makes the underlying mechanics more visible and thus more interesting to the player.

I think I have enough here to start working on a PR, but I'll wait a few days to see if there's comment on this direction before going ahead with the work.

[XygenSS]

Throwing a few ideas here.

'Visibly unclean water' (murky, cloudy, muddy...)
Stagnant natural water sources, obviously unsafe to drink.

'Visibly clean but risky water' (Just called water)
Flowing natural sources, stagnant manmade sources, Filtered water that does not remove microorganisms (charcoal filters etc)

• Water in toilet cisterns and water heaters should be safe enough but not fully safe, especially toilet water - basins could accumulate biofilms or mold, or be treated with toxic chemicals like drain cleaners etc. Toilet water definitely shouldn't give you parasites though. Toilet tank water should be safe to drink #30520

'Potable water' (Current clean water, but could instead be called potable, pure, purified, sterilized...)
Treated in some way that kills or deactivates microorganisms and/or removes chemicals. You should not be able to purify visibly unclean water without filtering it first, or enforce a filtering implement in the crafting recipe. Boiling, water treatment tablets, Lifestraw, bleach, other high tech filtering methods will net you potable water.

'Distilled water'
Mainly for use in chemistry, applied science recipes that involve water should enforce distilled water instead. Laboratory type locations should spawn jugs of distilled water.
Of course the survivor should be able to craft some using a distilling setup.
However it could be argued that since chemistry kit has a distilling quality, the survivor distills the water in situ in any recipe involving water; In that case there would be little to no merit towards distinguishing distilled water from potable water.

Then there's the problem with commercial bottled water, currently there's sealed bottles of clean water which is mostly useless past earlygame and sealed bottles of mineral water which is otherwise unobtainable. They could be collapsed into a bottled water which has +1 extra morale but shouldn't give you +10 extra hydration like mineral water currently does.

This would give you 4 or 5 types of water:
visibly unclean water, which is clearly unsafe
water, free of debris and mostly safe, but might carry microorganisms
potable water, which you can 100% rely on
bottled water, fancy pre-cataclysm water
and possibly distilled water.

[ZeroInternalReflection]

Filtering techniques should include using a commercial filter (e.g. LifeStraw, tablets, etc. which can go directly from water_murky -> water_sterilized), using an improvised filter using e.g. sand, charcoal, coffee filters (which would go from water_murky -> water, after which it could be boiled to get water_sterilized).

I'm currently trying to finish up #71971, which reworks the behaviour of water purification tablets (mostly so that they can no longer any amount of water instantly). The aquatabs you reference are also the ones I based the new version off of.

The system in that PR when you use the tablets is water->water_purifying (wait 40 minutes)->water_clean.
Changing it to go water_purifying->water_sterilized should be a simple JSON change.
Adding a path of water_murky->water_purifying->water_sterilized would require a check in the iuse function of "how dirty is the water you selected" to figure out if you need to use more tablets, but also shouldn't be too bad.

[nornagon]

@XygenSS I'm in agreement. Perhaps instead of "sterilized water" being the new thing, we use "clean water" to mean "water that is guaranteed safe to drink" (i.e. it's been sterilized), and introduce a new type for "bottled water" / "pure water" (maybe "spring water"?) that's more or less the same as mineral water.

@ZeroInternalReflection thanks for the PR reference, agreed that the tabs should be usable to sterilize murky water as well. I'm not sure about how that works with something like Aquatabs, if it takes longer and/or uses more tablets that should be relatively easy to model. Also, if we go with the suggestion from @XygenSS to make "clean water" mean "sterilized water", then your PR shouldn't need any JSON changes at all in that regard :)

[nornagon]

So here's the new transition graph, quite a bit simpler.

flowchart LR
water_murky -->|filter| water -->|sterilize| water_clean
water_clean -->|time unsealed| water

Loading

Pre-Cata bottled water would become water_spring and get a little morale boost.

[ZeroInternalReflection]

I'm not sure about how that works with something like Aquatabs, if it takes longer and/or uses more tablets that should be relatively easy to model

That's one thing I forgot to mention in my note above. The specific tablet I'm basing things off of calls for 1 tablet/L, or, if the water is cloudy or <4C, 2 tablets/L. (That's the Canadian website, but I believe the same tablet is sold in the US. The US website is just substantially more annoying)

That's a check that would need to happen in the iuse function, where after the player selects the water, we check "is it murky? Is it cold? Then we need bonus tablets"

It looks like the timeline/other instructions are the same, which is good because different processing times on water_purifying would probably be annoying.

[Nebnis]

Clean water/purified for sterilized/boiled water seems good enough for me. Maybe tap water for pre-cata water? Then add those to those heaters and other places. Would also differentiate from the mineral bottled water we have now.

[IdleSol]

water should become "safe-ish" to drink.

Fungal spores. If I ever met them in real life. I'd boil water ten times.

Remind me how the survivor interacts with the blob? Which is contained in the water. Did he gain immunity or was he lucky to survive?

flowchart LR
ocean --> ocean_shallow_water --> |always| salt_water_murky
swamp --> swamp_shallow_water -->|always| salt_water_murky
ocean --> ocean_deep_water --> |always| salt_water
ocean --> ocean_submerced_salt_water --> |always| salt_water
swamp --> swamp_deep_water -->|always| salt_water
swamp --> swamp_murky_shallow_water -->|always| water_murky
puddle ---> |always| water_murky
pool --> pool_water -->|chance? | water_murky
pool_water --> |chance? | water
pond --> pond_shallow_water --> |always| water_murky
pond --> pond_deep_water --> |always?| water_murky
fishing_pond --> fishing_pond_shallow_water --> |always| water_murky
fishing_pond --> fishing_pond_deep_water --> |always?| water_murky
stream --> stream_flowing_shallow_water -->|always?| water_murky
stream --> stream_shallow_water -->|always| water_murky
lakes --> lakes_shallow_water --> |always| water_murky
lakes --> lakes_deep_water --> |always| water_murky
lakes --> lakes_bulkhead --> |always| water_murky
lakes --> lakes_flowing_shallow_water --> |always| water
lakes --> lakes_flowing_deep_water --> |always| water
lakes --> lakes_submerced_water --> |always| water
river --> river_flowing_shallow_water --> |always?| water
river --> river_flowing_deep_water --> |always| water
sewer ---> sewage
sewage_treatment_plant --> STP_sewage --> sewage
sewage_treatment_plant --> STP_pool_water --> |always| water_murky
sewage_treatment_plant --> STP_shallow_pool_water --> |always| water_murky
natural_spring -->natural_spring_shallow_water --> |always| water
natural_spring -->natural_spring_deep_water --> |always| water_clean
water_heater --->|always| water_clean
hot_spring -->hot_spring_water --> |always ?| water_clean

Loading

There are still random encounters (?) with the ponds:
debug menu - m - n spawn map extra -

• s mx_pond
• t mx_pond_forest
• u mx_pond_forest_2
• v mx_pond_swamp
• w mx_pond_swamp_2

And I'm probably forgetting something.

[IdleSol]

flowchart LR
water_clean -->|time unsealed| water
water_murky -->|filter| water -->|sterilize| water_clean 
water -->|Distillation| distilled_water
salt_water_murky --> |???| salt_water --> |Distillation| distilled_water --> |mineralization| water_clean
salt_water --> |Electrodialysis| water
salt_water --> |Freeze–thaw| water

Loading

As for electrodialysis, it would be best to check with those who understand.

UPD. My opinion. I'm against spoiling clean water. Because it will lead to additional lags. Based on the topic: #71419 (comment) But that's not relevant to the topic.

[XygenSS]

Fungal spores. If I ever met them in real life. I'd boil water ten times.

Mycus-infected water and how to render it safe would be a cool mechanic but IMO out of scope for now. Mycus infestations are pretty regional, both in lore and ingame, there is little to no sign that mycus spores are spread everywhere. (real, non-anomalous fungal spores are everywhere, but that's just ordinary business and nothing our immune systems can handle... most of the time)

Remind me how the survivor interacts with the blob? Which is contained in the water. Did he gain immunity or was he lucky to survive?

Every living thing on Earth is contaminated with Blob including all survivors, some kept their sanity, some went feral, some recovered, but all of them including the survivor will zombify when killed.

The blob infection inside the survivor is what drives mutations as well

[IdleSol]

I'm talking about the blob being in the water. If a survivor drinks this water, will they mutate further? In other words, is it necessary to add a small amount of mutagens to the water?

[XygenSS]

No, mutagen is a specific thing. Drinking more blob when you're already blobbed does nothing

[XygenSS]

Btw @nornagon - Per Kevin in discord on the topic of the survivor distilling water per-recipe, "No that's not a remotely sensible thing to do, distillation can take a very long time and is very good at being run in big batches." So adding RO/DI water or distilled water is greenlit it seems.

[nornagon]

@XygenSS Yeah, RO/DI is a good idea for a followup, but this issue is mainly about collecting water for consumption, so I'll leave that for later.

@IdleSol I hadn't gotten to thinking about salt water, I think the only reasonable way for a survivor to convert salt water to drinkable water is through distillation, so that can maybe happen when we implement RO/DI water. Distilling murky salt water should be fine and directly produce distilled water; any particulate matter will remain in the undistilled portion. I'm not sure about freeze-thaw or electrodialysis for removing salt from water; I'm not familiar with those methods. As for mineralization of distilled water, how do you imagine that happening? What's the process for that?

And regards rot processing, I don't think the fact that it's currently under-optimized is a good reason not to have clean water spoil. The performance problems seem solvable :)

[IdleSol]

@nornagon

Think of it as a starting point. The main sources encountered in the game. Variants of tiles for these sources and my variant, what water can be taken from them. It can be simplified if necessary.

I was under the assumption that you might want to make different water for different sources. So I added the name of the source to the name of the tile.

I'm not sure about freeze-thaw or electrodialysis for removing salt from water

https://en.wikipedia.org/wiki/Desalination#Freeze–thaw
https://en.wikipedia.org/wiki/Desalination#Electrodialysis

It's more like content for labs and treatment plants. Maybe for oceanfront buildings, ships. I doubt it would be found in a garage.

Freezing and thawing of water. In the simplest case, it can be used for rough water purification. That is to turn murky water into water. It does not remove parasites or poisons. Based on the fact that ice begins to form around impurities. The main thing is to filter it in time.

As for mineralization of distilled water

There's a patent. Stumbled across it while looking for ways to do it. https://patents.google.com/patent/RU2616658C1/en

Fundamentally possible, with some simplifications and assumptions. Take salt water from the ocean and mix it with distilled water. Some scientific instruments are needed.

P.S. I apologize for the quality of the text.