Nerfing Decanter of Endless Water

[Thunderous Mojo]

The magic item rules set out in the DMG, apart from the magic item tables (though I prefer custom tables as well) is not very useful in actually running a D&D game, in my view.

Cool. I appreciate you sharing your opinion.

The 5e DMG is very clear that the "default" assumption is that magic items are "not for sale". It then further explains that if a DM decides to not use this "default" assumption, the Magic Item Rarity provides some guidelines on the cost associated with the sale of magic items.

Otherwise, the Magic Item rarity is a rough gauge of an items "level appropriateness"...(e.g. 1st level adventurers typically don't have nor find Rings of Invisibility). AD&D had no such guidelines...one either randomly rolled for treasure or chose it, and only experience from actual play, informed your decisions.

When you state that "Magic Item Rarity is useless to you as a DM", I interpret your statement as meaning that you have such an understanding of your own game that whatever item you elect to have available to the PCs you can "balance" the play with the item.

The rules suggest not giving an Oathbow to a 5th level PC, if you chose to do it, it is because you have it handled. Again, cool, and Cheers to That!🍾
Someone DM-ing for the first time, or creating their first campaign from whole cloth, may actually appreciate some guidance regarding this exact issue...which the DMG provides.

'Accidentally' handing out overpowered items has lead to many a campaign demise.

You stated you wanted more guidance for power levels between items in the same rarity category. Again, that is hard to do, as this depends on the particulars of a campaign.

I think most people can "eyeball" the fact that a Staff of Power is generally more powerful than a Potion of Supreme Healing. Of course not every campaign will have a Wizard or a Sorcerer or a Warlock in it. The DM has to be prepared to make such judgements, or failing that learn from missteps.

The "School of Hard Knocks" really is the best education for a DM, in my opinion.

Guidance from books helps, and I can certainly empathize with wanting more guidance that can directly help you specifically. Alas, the guidance provided in the DMG should primarily help those with the weakest grasp on how to make "balanced" choices.

If the 3PP book works better for you, that is great!
Decanters of Endless Water, Immovable Rods, Sovereign Glue, and Universal Solvent all are "low powered" items that have a penchant for causing mischief...(especially when used together😃). Typically this requires the conjunction of a clever player, the right item, and the right circumstances.

130K for a Decanter of Endless Water, means in effect the item is banned. There may not have been 130K worth or number of coinage in existence in England when Issac Newton was in charge of the English Mint. That is a gob smacking amount of currency to assume for economies based on coins of precious metals...especially pre-industrial ones.

[Xetheral]

I think it's the magic item creation rules on the DMG where rarity really starts to fall apart. Presumably Sovereign Glue and Universal Solvent are Legendary rarity simply because there isn't much demand for them. But under the magical item creation rules, one bottle of either one requires 250,000 gold and 80,000 hours to produce. It's hard to imagine why any doses exist at all if they are that expensive and time-consuming to make.

I suppose the legendary rarity for these items could be a feedback effect: they were expensive to produce, so no one produced them, so they became rarer, and thus even more expensive to produce, until eventually they became merely the stuff of legends and almost impossible to produce. But a game world that operates on such a principle is really only good for a farcical campaign.

[Sigreid]

I'd actually probably be down to buy a WoTC book that was just magic item formulas.

[Randel]

There's also the Alchemy Jug that can produce 12 gallons of salt water a day along with all sorts of other stuff like honey, beer, wine, mayonnaise, etc. It's an uncommon item which the Sane Magic Item Price thing lists as costing 6,000 gp, although I could easily see it being priced under 1,000 gp since it's utility is situational and not for combat.

If you're running a ship, I'd wholeheartedly recommend making alchemy jugs cheap enough that the players can get more than one. Get some barrels, tubs, buckets, etc to store seawater for the elves and use the jugs to keep them filled. Then, if you've got enough seawater then the jugs can produce stuff like beer, honey, vinegar, etc to help keep people fed.

[Magic Myrmidon]

https://amp.reddit.com/r/dndnext/com...nd_discerning/

I also had problems with Sane Magic Item prices. I found this spreadsheet for an alternative, and it's been great. Having the prices side by side also allows me to decide whether either price is reasonable, too.

[Bardon]

Just to be clear, if I understand correctly they want another Endless Decanter of Seawater not fresh. If so, even if you're wedded to the Sane guide I'd definitely drop the price because it doesn't produce potable water, so many of the economy-breaking issues described don't apply.

[stack]

It is Eberron, so utility magic is common. There isn't a setting reason to make it expensive, assume its function is reduced to what is needed for aquatic elf comfort.

If it is providing benefits that don't impact the party, there is no reason it needs to have a significant cost.

[Unoriginal]

I think it's the magic item creation rules on the DMG where rarity really starts to fall apart. Presumably Sovereign Glue and Universal Solvent are Legendary rarity simply because there isn't much demand for them. But under the magical item creation rules, one bottle of either one requires 250,000 gold and 80,000 hours to produce. It's hard to imagine why any doses exist at all if they are that expensive and time-consuming to make.

I suppose the legendary rarity for these items could be a feedback effect: they were expensive to produce, so no one produced them, so they became rarer, and thus even more expensive to produce, until eventually they became merely the stuff of legends and almost impossible to produce. But a game world that operates on such a principle is really only good for a farcical campaign.

Sovereign Glue literally requires a Wish to remove, if you don't have Universal Solvent. It's pretty Legendary to me.

[ProsecutorGodot]

Sovereign Glue literally requires a Wish to remove, if you don't have Universal Solvent. It's pretty Legendary to me.

Oft forgotten fact, Oil of Etherealness also removes it.

Which might be why Universal Solvent is legendary... Who would go through all the trouble to make that if a more expedient and less costly alchemical solution (that is useful in other ways to boot) already exists?

[Xetheral]

Sovereign Glue literally requires a Wish to remove, if you don't have Universal Solvent. It's pretty Legendary to me.

Sure, the bond it creates is nearly indestructible, but it doesn't provide any additional strength to the bonded objects. Unless you're bonding adamantine or artifacts it's pretty trivial to cut away the glued surface and then cast Mending to repair the damage from your (literal) hack job.

In other words, having a bond stronger than the objects it is bonding isn't particularly useful, so who cares whether the bond is indestructible rather than merely strong enough to not be the point of failure? Sure, one could write a campaign where there is a need to permanently bond two artifacts to each other, but without a ton of contrivance Sovereign Glue has about the same level of utility in the game world as epoxy. So, it's useful (particularly if non-magic adhesives are limited in the campaign world), but not particularly valuable. No one is going to make (or commission others to make) a bottle of it unless either they need it themselves, or they think they can sell it for a profit. At a quarter-million gold and 80,000 hours per bottle (plus labor costs, for a commission), it's hard to see why anyone ever bothered making any of it at all. It's literally a career's worth of work (27 years!) for a spellcaster to make a single bottle of adhesive that in practical terms isn't significantly more useful than what can be found in any modern drugstore.

[Coidzor]

Just to be clear, if I understand correctly they want another Endless Decanter of Seawater not fresh. If so, even if you're wedded to the Sane guide I'd definitely drop the price because it doesn't produce potable water, so many of the economy-breaking issues described don't apply.

There are still ways to break the economy that can be achieved by being able to produce a lot of salt water, but you have to work harder because evaporating salt water into salt takes time/energy/space and harvesting it requires labor, and so there are more moving parts to the scheme.

Admittedly, salt is 5 cp per pound when it was once 5 gp per pound or sp per pound in previous editions, which has tended to cut down on discussions of such schemes.

[Xetheral]

There are still ways to break the economy that can be achieved by being able to produce a lot of salt water, but you have to work harder because evaporating salt water into salt takes time/energy/space and harvesting it requires labor, and so there are more moving parts to the scheme.

Admittedly, salt is 5 cp per pound when it was once 5 gp per pound or sp per pound in previous editions, which has tended to cut down on discussions of such schemes.

A Decanter of Endless Saltwater is also still good for powering perpetual motion machines, albeit with a higher cost in replacing components damaged by corrosion.

[Sigreid]

A Decanter of Endless Saltwater is also still good for powering perpetual motion machines, albeit with a higher cost in replacing components damaged by corrosion.

THinking a ship powered by a paddle wheel?

[Fable Wright]

https://amp.reddit.com/r/dndnext/com...nd_discerning/

I also had problems with Sane Magic Item prices. I found this spreadsheet for an alternative, and it's been great. Having the prices side by side also allows me to decide whether either price is reasonable, too.

Decanter of Endless water: Is it worth... 135,000gp, or 300gp?
Weapon of Warning: 60,000gp, or 400?

Honestly, in the end, I'm inclined to go for the Discerning Merchant's Price Guide valuations. Having a holy avenger worth 165,000gp and a decanter of endless water at 135,000gp is... beyond nuts. When an extraordinarily powerful weapon, a +3 bow/sword/whatever, is priced at 16k? It makes no sense whatsoever.

[Xetheral]

THinking a ship powered by a paddle wheel?

As one of many possible options, yes.

[stack]

THinking a ship powered by a paddle wheel?

Paddle wheel is an unnecessary step. Mount it below the waterline and let it push you directly. You just need a way to vector the thrust.

[Sigreid]

Paddle wheel is an unnecessary step. Mount it below the waterline and let it push you directly. You just need a way to vector the thrust.

I don't think that would work with larger vessels. /shrug

[Xetheral]

I don't think that would work with larger vessels. /shrug

The amount of kinetic* energy created by the Decanter is fixed. Whether you mount it as a waterjet or use it indirectly on a paddlewheel (or turbine), you get similar maximum power, modified for any efficiency losses. The waterjet method has fewer mechanical losses (from e.g. friction of the wheel), and so should be slightly more efficient than the paddlewheel. On the other hand, by gearing the paddlewheel, one would get a lot more control over the boat's acceleration.

*The Decanter creates other types of energy too. The easiest to access would be gravitational potential energy--just put the Decanter on a mountain and use the height to create additional water pressure. One could also potentially tap the thermal energy of the water, although the method would depend on whether the Decanter produces water at a fixed temperature or at ambient temperature. By far the most energy produced by the Decanter is in the rest-mass energy of the new water, but good luck trying to access that.

[stack]

I don't think that would work with larger vessels. /shrug

Is spraying onto a paddle wheel going to transfer the kinetic energy move efficiently than spraying directly into the water?

It can push a 200 pound object 15 feet in 6 seconds. Can't get precise numbers out of this, since it also pushes a 1 ounce object the same distance and we have no numbers for the coefficient of friction (though large volumes of water will help reduce that).

Could come at it from the other side. 30 gallons/round = 300 gallons/minute. It shoots 30 feet regardless of orientation, so call that 30 feet of head. Specific gravity is 1. Efficiency is 1 (magic!)

Pwhp = q h SG / (3960 μ)

where

Pwhp = water horsepower (hp)

q = flow (gal/min)

h = head (ft)

SG = 1 for water Specific Gravity

μ = pump efficiency (decimal value)

300*30*1/3960 = 2.27 horsepower. So the power potential, regardless of how you employ it, is useful but limited. Any way you employ this power will be inefficient, so lets call it about 2 hp. Could run small boat.

Edit: Xetheral makes good points about gravity and temperature. Since it apparently comes out as liquid, even if it emerges at ambient temperatures, the latent heat required to change state in extreme environments could still be useful.

[Sigreid]

The amount of kinetic* energy created by the Decanter is fixed. Whether you mount it as a waterjet or use it indirectly on a paddlewheel (or turbine), you get similar maximum power, modified for any efficiency losses. The waterjet method has fewer mechanical losses (from e.g. friction of the wheel), and so should be slightly more efficient than the paddlewheel. On the other hand, by gearing the paddlewheel, one would get a lot more control over the boat's acceleration.

*The Decanter creates other types of energy too. The easiest to access would be gravitational potential energy--just put the Decanter on a mountain and use the height to create additional water pressure. One could also potentially tap the thermal energy of the water, although the method would depend on whether the Decanter produces water at a fixed temperature or at ambient temperature. By far the most energy produced by the Decanter is in the rest-mass energy of the new water, but good luck trying to access that.

Is spraying onto a paddle wheel going to transfer the kinetic energy move efficiently than spraying directly into the water?

It can push a 200 pound object 15 feet in 6 seconds. Can't get precise numbers out of this, since it also pushes a 1 ounce object the same distance and we have no numbers for the coefficient of friction (though large volumes of water will help reduce that).

Could come at it from the other side. 30 gallons/round = 300 gallons/minute. It shoots 30 feet regardless of orientation, so call that 30 feet of head. Specific gravity is 1. Efficiency is 1 (magic!)

Pwhp = q h SG / (3960 μ)

where

Pwhp = water horsepower (hp)

q = flow (gal/min)

h = head (ft)

SG = 1 for water Specific Gravity

μ = pump efficiency (decimal value)

300*30*1/3960 = 2.27 horsepower. So the power potential, regardless of how you employ it, is useful but limited. Any way you employ this power will be inefficient, so lets call it about 2 hp. Could run small boat.

Edit: Xetheral makes good points about gravity and temperature. Since it apparently comes out as liquid, even if it emerges at ambient temperatures, the latent heat required to change state in extreme environments could still be useful.

I was actually thinking in terms of water weight built up as a wheel section fills.

[Xetheral]

Edit: Xetheral makes good points about gravity and temperature. Since it apparently comes out as liquid, even if it emerges at ambient temperatures, the latent heat required to change state in extreme environments could still be useful.

Coming out at ambient would probably be even easier to use than at room temperature. It's easier to change the ambient temperature of the Decanter than it is to move the Decanter to an environment where ambient is noticably different than room temp. And then you get phase-change shenanigans on top. :)

EDIT:

I was actually thinking in terms of water weight built up as a wheel section fills.

That could work, but even with perfect efficiency you'd need a 9.10 meter diameter wheel to get up to the same 2.27 horsepower that stack calculated for the waterjet. That's an impractically large wheel for most boats. But the taller the wheel the more horsepower is available (since basically you're extracting gravitational potential energy), so you're right that for the biggest boats this method would work better than a waterjet. You'd be wasting the kinetic energy, though, so a hybrid approach with a small pressure-driven turbine located above the giant wheel that drains into the buckets would be more efficient.

Edit Edit: Although, the mass of the wheel will increase (at least) with the square of its diameter, whereas the available horsepower only increases linearly with the diameter. So depending on the materials the boat is made out of and the displacement of the rest of the boat, at some point you'll start to get diminishing speed returns from a larger wheel.

[JoeJ]

Paddle wheel is an unnecessary step. Mount it below the waterline and let it push you directly. You just need a way to vector the thrust.

The decanter won't push anything weighing more than 200 pounds, so that will only work on very small vessels. And even then you'd have to point the stream at the boat rather than the water, because there doesn't appear from the description to be any recoil.

[Xetheral]

The decanter won't push anything weighing more than 200 pounds, so that will only work on very small vessels. And even then you'd have to point the stream at the boat rather than the water, because there doesn't appear from the description to be any recoil.

Interesting interpretation. It's certainly possible: the Decanter is already violating conservation of energy in a huge way, so maybe it also violates conservation of momentum too. Of course, there is an easy workaround: just have the Decanter vent into an internal chamber on the ship that itself is ducted out the back. Also, interpreting the Decanter to violate conservation of momentum opens up another can of worms: it's already got unlimited delta-V as a rocket engine, but if you ignore conservation of momentum you can use it to make a reactionless drive.

[stack]

No pressure limitations either; could make an interesting hydraulic system.

edit: engineers + magic items = trouble

[Sigreid]

Coming out at ambient would probably be even easier to use than at room temperature. It's easier to change the ambient temperature of the Decanter than it is to move the Decanter to an environment where ambient is noticably different than room temp. And then you get phase-change shenanigans on top. :)

EDIT:

That could work, but even with perfect efficiency you'd need a 9.10 meter diameter wheel to get up to the same 2.27 horsepower that stack calculated for the waterjet. That's an impractically large wheel for most boats. But the taller the wheel the more horsepower is available (since basically you're extracting gravitational potential energy), so you're right that for the biggest boats this method would work better than a waterjet. You'd be wasting the kinetic energy, though, so a hybrid approach with a small pressure-driven turbine located above the giant wheel that drains into the buckets would be more efficient.

Edit Edit: Although, the mass of the wheel will increase (at least) with the square of its diameter, whereas the available horsepower only increases linearly with the diameter. So depending on the materials the boat is made out of and the displacement of the rest of the boat, at some point you'll start to get diminishing speed returns from a larger wheel.

That is what I was thinking, but I also think Animate Object would be a better way of propelling a ship.

[Xetheral]

No pressure limitations either; could make an interesting hydraulic system.

edit: engineers + magic items = trouble

Excellent point. This seems apropos, although more for weaponizing the Decanter than for hydraulics. Just substitute a smaller straw to keep the water's velocity relativistic. No limitations on how to attach the straw to the Decanter--any clamp that can survive 200 lbs of force will work under JoeJ's interpretation. :)

With a small-enough straw, we can get the kinetic energy up around the rest-mass energy when the water gets to 0.9c. That's in the neighborhood of 10^19 joules every six seconds, and unlike the rest-mass energy it will be in a usable form (assuming you have a use for ultra-high-energy plasma anyway).

Hmm, one difficulty will be what to make the straw out of. We don't want it to vaporize instantly. A Wall of Force with overlapping 10' x 10' panels should work nicely, leaving a square hole of arbitrarily small size in the middle. Since the wall is immobile and the Decanter doesn't experience recoil, we don't even need a clamp.

[stack]

There are people who DON"T have a use for ultra-high-energy plasma?

[JoeJ]

Excellent point. This seems apropos, although more for weaponizing the Decanter than for hydraulics. Just substitute a smaller straw to keep the water's velocity relativistic. No limitations on how to attach the straw to the Decanter--any clamp that can survive 200 lbs of force will work under JoeJ's interpretation. :)

With a small-enough straw, we can get the kinetic energy up around the rest-mass energy when the water gets to 0.9c. That's in the neighborhood of 10^19 joules every six seconds, and unlike the rest-mass energy it will be in a usable form (assuming you have a use for ultra-high-energy plasma anyway).

Hmm, one difficulty will be what to make the straw out of. We don't want it to vaporize instantly. A Wall of Force with overlapping 10' x 10' panels should work nicely, leaving a square hole of arbitrarily small size in the middle. Since the wall is immobile and the Decanter doesn't experience recoil, we don't even need a clamp.

And when you do all that, the water still shoots only 30 feet and only has enough power to do 1d4 bludgeoning damage (to a creature that fails its save) or move a 200 lb. or less object 15 feet. Kinetic energy is not a meaningful concept; the decanter follows the law of conservation of results. That is, the water is magically controlled to produce certain results and nothing further.

[Xetheral]

There are people who DON"T have a use for ultra-high-energy plasma?

I mean, I think the aquatic elf from the OP probably plans to use the Decanter for the salt water, rather than as a 4.5(ish) horsepower perpetual motion machine (using the turbine+gravitational waterwheel design, assuming conservation of momentum) or as a weapon to destroy cities (using the Decanter and Wall of Force nozzle/blast shield, assuming violation of conservation of momentum).

You know, under the violates-conservation-of-momentum interpretation, the Decanter is easily worth the otherwise-problematic 135,000 GP price.

And when you do all that, the water still shoots only 30 feet and only has enough power to do 1d4 bludgeoning damage (to a creature that fails its save) or move a 200 lb. or less object 15 feet. Kinetic energy is not a meaningful concept; the decanter follows the law of conservation of results. That is, the water is magically controlled to produce certain results and nothing further.

Sure, based on the item description the 30 gallons of water (travelling at 0.9c) hit a person, possibly deal 1d4 damage, and maybe knock them prone. The item's effects are now finished, and the description no longer controls. The water is still around, however, and does everything normal water would, which, in the case of normal water travelling 0.9c, involves lots of excitement.

Real answer: no, I would not use the item this way at my table, or let the PCs do so. It is fun to think about the implications though, especially when trying to enforce one aspect of the description (a lack of mention of any recoil) makes the implications much worse, rather than more palatable. :)

More broadly, all of our analysis is flawed anyway--the moment you start discarding conservation of energy and/or momentum, all of the other physics equations probably change too.

[JoeJ]

Sure, based on the item description the 30 gallons of water (travelling at 0.9c) hit a person, possibly deal 1d4 damage, and maybe knock them prone. The item's effects are now finished, and the description no longer controls. The water is still around, however, and does everything normal water would, which, in the case of normal water travelling 0.9c, involves lots of excitement.

The water hangs around, but after it goes 30 feet it's not travelling at 0.9 c. It's just laying there in puddles on the floor. It never was travelling at 0.9c; it was travelling 30 feet per round. Even if you put it through a tiny straw, both the amount and the speed remain unchanged. Magic and physics are not only separate, they have different underlying logics.