I had a game in which there was temple for a local god. One of the practices of the temple was to make sure that the river that flowed through the town was clean. They managed this by doing what the Romans did, with public bathrooms. All of the plumbing comes to a spot at the temple where they have clerics casting purify food and drink on the sewage.

The description of the purify food and drink spell says:

All nonmagical food and drink within a 5-foot-radius sphere centered on a point of your choice within range is purified and rendered free of poison and disease.

Regardless of why they're using this, would Purify Food and Drink (by RAW) actually clear the sewage from the water? Or would their efforts be in vain and it would still be nasty sewage water, unfit for drinking? (Note: They have as many clerics as is necessary.)


Pretty sure it's clean.

First, we know that it's at least potable. Clearing out all poison and all disease means that you can drink it without harm - anything in it that might harm you would either be a poison or a disease. Whether it's foul-tasting or not is less certain, but I'm pretty sure that that's taken care of too. It says that the stuff is "purified", in addition to having poisons and diseases removed. If what you're starting with is befouled water, then the natural effect of purifying it is to render it into "pure water". How this works with food and non-water drink is a little more interesting, but for water it looks pretty clear.

Now, how that purification occurs, and what happens to the foulness as a result is a different question, and up to your DM. It might even vary from god to god. Perhaps there's a god of filth out there who takes it for himself because he likes the stuff.

  • \$\begingroup\$ Potable isn't the same as having no disease or poison. You can't drink liquid cement, petrol, or mercury, but neither have diseases or poison. \$\endgroup\$ – BlueMoon93 Mar 9 '18 at 13:37
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    \$\begingroup\$ @BlueMoon93: Mercury is a poison. If you remove all of the poison from it, you have nothing left. Petrol probably counts as the same. Technically, I suppose that you're correct that you could have something that wasn't itself toxic but that would react with stomach acids or solidify in the gut or something and thereby do some damage, but that's not what we're talking about here. \$\endgroup\$ – Ben Barden Mar 9 '18 at 14:27
  • \$\begingroup\$ @BenBarden Personally, I would say that the majority of poisons only do damage because they react with something else already in your body, or behave in some way that the body can't handle. That said, it's very hard to draw a useful line since even pure water will kill you if you have enough of it, and plenty of clearly poisonous things are harmless in small enough quantities. \$\endgroup\$ – Kamil Drakari Mar 9 '18 at 15:55
  • \$\begingroup\$ @bluemoon it is implied in the spell that the stuff being targeted by the spell is edible. cement, petrol are not drinks, and mercury is poison. It would require a separate question to settle this, but I'm pretty sure that the spell won't work on those materials. \$\endgroup\$ – Mindwin Mar 9 '18 at 17:32
  • \$\begingroup\$ @mindwin i dont think it will either, i agree with the top voted answer in fact \$\endgroup\$ – BlueMoon93 Mar 9 '18 at 19:05

The opening words of the spell description seem to be critical to how one interprets the intent of this spell:

All nonmagical food and drink within ...

Raw sewage is not "food and drink" in the ordinary sense of the words, any more than mercury and oak doors or green slime and caltrops are, even though you might be able to find something that might achieve a degree of sustenance from consuming an oak door or a caltrop.

If you dropped your lunch into raw sewage and fished it back out, that noisome and ruined lunch would be a suitable target for this spell.

If you dropped a poorly-sealed wineskin into it and it got a little sewage in it before you got it out, that would similarly be "drink" capable of being purified.

Not everyone will read it this way, but as I read it, it seems to be what the ordinary sense of the words mean.

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    \$\begingroup\$ Given water is drinkable, Purify Food and Drink should remove the impurities from water. Still though, +1, as I believe you touch on a very important point. Perhaps the spell can only remove dissolved impurities from the water, which simply immediately becomes re-dirtied by all the non-water, non-edible "floaties" swirling around... \$\endgroup\$ – Robotnik Mar 9 '18 at 1:29
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    \$\begingroup\$ Sewage is horribly befouled water. As such, I would class it as drink. The spell turns it into pure water. \$\endgroup\$ – Loren Pechtel Mar 9 '18 at 3:12
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    \$\begingroup\$ +1 I agree with this interpretation, but I think the rules could be fairly read differently. \$\endgroup\$ – Jack Aidley Mar 9 '18 at 11:30
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    \$\begingroup\$ If there is a certain concentration of sewage where it is not treated as water, (and so would not be purified by this spell), how much water would you need to add to transform it from "Raw Sewage" to "Dirty Water"? \$\endgroup\$ – Michael Richardson Mar 9 '18 at 14:37
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    \$\begingroup\$ @Mindwin Terms in the rules without rule-specific meaning use their normal English meaning. Sewage contains water, but I don't agree with calling it a drink. Just like I would never call Windex a drink, despite the fact that it is mostly water. A disgusting river of waste that also includes something that would be drinkable by itself is not the same thing as simply a drink, even a drink that contains some toxins or diseases. You might as well "purify" a human into ~13 gallons of water - easy, clean kill. \$\endgroup\$ – Zeus Mar 9 '18 at 20:06

If it was just dirty water, I doubt there'd be much to argue about, as water is pretty clearly drink. The spell would kill all bacteria, viruses, and remove both organic and heavy metal toxins.

The issue as I see it is the large lumps of poop. These aren't food, so aren't purified. If only the water surrounding and between the poop is purified, it will become besmirched again quite quickly.

So, can the spell remove large lumps of solid matter?

In other circumstances, would the spell remove a mouse from inside your loaf of bread? Probably not, as the mouse is not a disease. The mouse also would not be 'food' to most casters, so any bacteria inside the mouse would not be cleared. The mouse would likely be completely unaffected, and could thus defecate and dirty your food after the spell was cast.

So, I'd argue that RAW the spell will not result in clean water as it would become re-polluted by poop, which I believe would not be a target/recipient of the spell.

Of course, if the DM says it works, then it works. Probably these clerics have a friendly god who just goes along with their intentions and grants the effect they want. Gods can do that, they're not really bound by the rules.

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    \$\begingroup\$ The spell says it 'purifies' the food and water. Would you consider water with poop in it pure? I would not. And, as for mice, would you apply the same reason to weevils in biscuits? Parasitic worms? Flies? Maggots? Where do you put your cutoff? \$\endgroup\$ – Jack Aidley Mar 9 '18 at 9:27
  • \$\begingroup\$ @JackAidley That is actually an interesting conundrum, since the spell does say that it purifies the drink, aka the water, but not the body of water. So, in fact, an argument could be made that it literally only purifies the water of toxins and microorganisms, but not of dirt and other things because while they're in the water, they're not really part of the water (as in, solved within the liquid that is purified). Then again, it'd be trivial to filter out any solid matter before purification. \$\endgroup\$ – Suthek Mar 9 '18 at 13:45
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    \$\begingroup\$ My dog disagrees with your assertion about the relationship between poop and food. \$\endgroup\$ – Tim Sparkles Mar 10 '18 at 2:25
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    \$\begingroup\$ I'm pretty sure that if your dog casts the spell, the results will be different to if a human casts the spell \$\endgroup\$ – Sir Adelaide Mar 12 '18 at 23:36

This is one of those situations where you need to let the spirit of the spell override it's wording. It's a spell, not a computer program.

It's clearly a spell that's used to to make water that's unsuitable for drinking suitable, so yes I would say that it can turn sewerage into drinking water.

Unless the GM has a specific story reason not to...

  • \$\begingroup\$ I agree with this. Sewage water is, to describe its basic nature, water. People drink from rivers and streams, some of these rivers and streams get contaminated from time to time. \$\endgroup\$ – Robert Columbia Mar 9 '18 at 13:41

The rules-as-written on whether the spell can purify sewage is, in my opinion, vague enough that it is a reasonable interpretation that it could even though I would not interpret it that way as a DM myself.

A bigger problem is the volume of sewage. Purify is a first level spell and thus limited in casting, and each cast purifies a smidge under 15000 litres a cast assuming you can completely fill its spherical effect - which is difficult to achieve, but we've leave that to one side - which sounds a lot but consider that historical estimates of Roman water usage were an incredible 330-420 gallons per capita per day (er, US gallons, I think judging by the source), or somewhere around 1200-1500 litres a day. At that kind of usage you'd be able to deal with just 10 or 12 people per cast of Purify. A town of 1000 would require about a hundred castings per day. Now, maybe you think those numbers are too high - the Romans sure bathed a lot - so you could reasonably go down from there to, say, 300L per person per day but that would still require one casting of Purify per 50 people.

Upshot: you're going to need a lot of Clerics to do this.

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    \$\begingroup\$ It's a popular temple \$\endgroup\$ – Peregrine Lennert Mar 9 '18 at 12:14
  • \$\begingroup\$ The paper that you'd linked about Roman water usage seems to be all about how such figures aren't reliable. It concludes: "It appears, therefore, that we cannot trust our books on antiquities, and that until other evidence is produced we should believe that the Roman uses for water, and consequently the water supply, were less than those of a modern metropolis.". \$\endgroup\$ – Nat Mar 9 '18 at 19:16

I would say they combine it with current day methods of cleaning water.

They have huge holy pools. When one is filled up the other one gets filled and the sewage filled pool gets to rest for a day.
After a day the pool is drained from the top down(a board that gets lowered gradually as cleanish water flows out. with heavy cloth still in front to hold back any small sludge particles.) Then that stream fills up smaller pools near a cleric, when that pool is full it switches to another. Meanwhile the cleric with his full pond casts his purify water and drains the pool into the river and moves to the next that just filled up.

When the large sewage collecting pool is empty to the point of there is only the sewage sludge left, the workers gather the sludge and transport it out to the farm fields where it's sold as manure(human excrement is a very potent fertilizer).

This way you have also a source of income for the temple and a good reason why they keep doing it.

  • \$\begingroup\$ Other than the reason that the god it's for would get really angry if they fouled up the river? \$\endgroup\$ – Peregrine Lennert Mar 9 '18 at 12:15
  • \$\begingroup\$ People tend to forget over time why they do something, or get less passionate since the last extinction level event, and greed is a good incentive. If you've been purifying water for 20 years without anything happening, either the village becomes bored with it, not "seeing the need" or the clerics wish to do more interesting stuff. But if there's money, gain, produce involved people tend to stay on point. Because the water goes to the river, it's free for the civilians. They need another "critical" reason to exist. The manure manufacturers, "those shit clerics" they whisper with a snicker. \$\endgroup\$ – Tschallacka Mar 9 '18 at 12:59

I've been thinking about this a lot too an I think it would first have to go through a basic septic system and then most of the sludge and such is removed. After that, it would be easier to purify, especially for a 1st level spell. I've been toying with the idea of a grates enchanted with purify food and drink so then the need for constant clerics is lessened, but I'm not sure if that is possible.

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    \$\begingroup\$ Welcome to RPG.SE! Take the tour if you haven't already, and check out the help center for more guidance. I'm not sure this really answers the question of whether purify food and drink would work in this case (though it seems like the answer it implies is "not on its own"); can you elaborate on your point and support it by citing evidence or experience? \$\endgroup\$ – V2Blast Oct 8 '19 at 5:26

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