What does water cost and weigh per gallon?

Question

In the Player's Handbook it states only that a waterskin costs 2 silver pieces, and a barrel 2 gold pieces. With some research I learned that a waterskin can hold 1/2 a gallon and a barrel can hold 40 gallons.

But how much does the water cost and weigh? Even if you find a place to buy water, the Player's Handbook doesn't state how much it costs per gallon. Nor does it says how much it weighs per gallon. I couldn't find the answer in the Player's Handbook and I'm not familiar with gallons and pounds.

Answer 1

What makes you think that a well or stream costs money to use, by default? The DM is able create any sort of water monopoly he likes, but in general streams, wells, and lakes are plentiful and unguarded. DnD has a history of heavily implying that while Ale costs money at an Inn, the water is free.

As for its weight. When it is not explicitly discussed, 5th edition DnD mechanics are assumed to emulate real-world mechanics, such as the density of molecules and the laws of physics. So Water weighs approximately 8 lbs per gallon. This works out very neatly with the stated weight of a full waterskin, which would then be 1 pound for the skin and 4 for the water.

Answer 2

It's a common myth that Medieval people didn't drink water. Actually they did, just didn't drink from a bad source. And, when it came to sources, yes, there were plenty of unpolluted sources of water, because they weren't children and made an effort not to contaminate their own water sources with poop. (Plus, when it came to rivers, they did not often drink from those, just swam and fished there).

Get into a mega-city, like London, with a population of 10,000, and then, fresh clean water is more difficult to come by. But, even then, there were wells and people did not pay to use them--except when they gave a coin to a water-carrier to bring back water. A private conduit was paid for, and at an inn, if you order water, yes, that's from the day's supply, and they probably have a glass included in the meal. But if you drink too much water they might ask you to pay, and certainly would not allow you to fill up your whole water skein (unless you flirt with the staff). You likely will pay if you take a bath, because that's a LOT more water and labor...although that water is likely from the river, and not drinkable. Using well water might happen at a more upscale establishment.

When running D&D, I assume that water is free, UNLESS, there are specific circumstances making water rare. The PCs might have to go and wait in line for the well for like an hour, but, they'll get the water for free. I find this is a great time to introduce quest lines and rumors, actually.

I think the creators of the game also assume it is free and therefore do not include it.

Gallon= about 8 pounds, I think you can figure it out from there.

Answer 3

How Much Does Water Cost?

I don't know if there is a RAW listing of the price of water. The thing is, there are so many skills / spells that are provided to players to find or conjure up a source of water that the game's designers simply assumed that in the Forgotten Realms setting, water is too cheap to assign a price to it. But, do not fret - we can give water a price by assigning to it some reasonable bounds that are specified in the RAW.

• A gallon of ale costs 2 silver pieces (PH, pg. 158).
• A waterskin is listed at 2 silver pieces. When full, a waterskin contains 4 US liquid pints. (PH, pg.150)
• Lifestyle expenses "cover your accommodations, food and drink, and all your other necessities" (PH, pg.150). If you live a Modest lifestyle (1 gp / day), "[y]ou don't go hungry or thirsty" (PH, pg.151). It's likely that at least 50% of the daily cost goes to accommodations alone (think renting an apartment). Conservatively, let's assume the remain 50% is split halfway between food & water. Lifestyle expenses thus indicate the daily price of water is 0.25 * 1 gp = 2.5 sp.

Again, the RAW doesn't say anything about minimum water intake for a player character (perhaps this varies too much between races). However, we can guess "not going thirsty" means you take in enough water on a daily basis to remain healthy. However, the WHO (World Health Organization) has published a study on "Water Requirements, Impinging Factors, and Recommended Intakes":

the minimum water requirement for fluid replacement for a 70-kg human in a temperate zone equates to 3L per day... for an individual the same size but in a tropical zone equates to 4.1-6L/day

-- pg. 8

Those minimum water requirements average out to 4.5L ~= 1.2 US liquid gallons. Some estimates:

• 1 gallon of Ale (presumably more expensive than water) = 2 sp.
• 1 gallon, or 2 full waterskins * 2 sp = 4 sp.
• 2.5 sp / 1.2 gallons of minimum water intake ~= 2 sp per gallon.

Purchasing from an inn? If an inn sells ale by the gallon at the price of 2 silver prices (as listed on pg. 158 of PH), then water sells for 2 sp at the most (As @JackAidley commented, NOTE: this is implementation-specific. Think about how the Inn gets its water - how difficult it is to obtain potable water will likely determine the Inn's price for water. Does it have to pay a fee for access to the city's reservoir? Is the Inn convenient built on top of an underground spring filled with potable water?)

Purchasing from a local source? If the water source charges local customers for water (say, a government-run water distribution system requires a fee for you to collect water) then Modest lifestyle expenses suggest the most you'd spend in a day is 2.5 sp, at 2 sp per gallon while Squalid lifestyle expenses suggest you might get away with less than 2 sp (in this case, I'd imagine the water isn't guaranteed to be clean for consumption).

Purchasing from a merchant? If the merchant is selling water in the form of full waterskins, the most you'd spend per gallon of water is 4 sp for 2 full waterskins at 2 sp per waterskin (as listed on pg. 150 of PH).

How Much Does Water Weigh?

Without a container, this is a simple calculation. From Wikiepdia, "Kilogram":

(Under Definition section)... The final kilogram ... had a mass equal to the mass of 1 dm^3 of water at its maximum density, approximately 4 °C.

1 dm^3 = 1 L = 1 kg (by definition). 1 gallon ~= 3.8 kg = 8.4 lbs.

Otherwise, the answer will depend on the container that is being used to carry the water. The following numbers are only useful

• A full waterskin weighs 5 lbs (PH, pg. 150). A waterskin has a maximum capacity of 4 pints of liquid (PH, pg. 153). 8 pints = 1 gallon, so 2 5-lb full waterskins carry 1 gallon of water.
• A (presumably full) flask of holy water only weighs 1 lb (PH, pg. 150).

Answer 4

As has been noted in other comments and answers, since the cost of water is not explicitly defined you can feel free as a DM to improvise. However, this is often easier said than done, after all, how does one put a price on something as essential as water?

What I would recommend is to consider the social and economic pressures people in your game world feel, and how they might relate to real world situations. For example:

Real World Examples

• Brewing has historically been a reliable way of decontaminating water (there are a few good sources in this thread), and so it might not have been not uncommon for beer or wine to be cheaper than clean, potable water! In the PHB (p. 158), a gallon of ale is priced at 2sp, so in a community without access to magic, a gallon of clean water might be equally, or even doubly expensive, considering the work that goes into treating unsafe water.

• In North America, a 500ml bottle of water can cost up to $2.00 at a vending machine, an enormous markup considering bottling companies acquire water for about $2/million litres. Most of the price of these bottles comes from the costs of distribution and retail. Thus, if your PCs stay in a town where the nearest water source is miles away and spellcasters aren't readily available, it might be realistic to mark up the price of water to equal the price of any other shipped good.

Note that in both my examples, I've added the same caveat; spellcasting is probably the most reliable way of producing good clean water, likely via the Create Water (PHB p.229) or Purify Food and Drink (PHB p.270) spells, both of which are available to 1st level Clerics and Druids. A Cleric might provide pure water for free at a temple, or charge a nominal fee (maybe a donation to said temple) to purify water by the barrel.

As for the weight of water, I will defer to Jonathan Wisnoski's previous answer: Real world values are the most appropriate to use here.