Maybe ‘the thirsty’ are not the ones who live in water or are made of fire (since they can’t have water). 

What if we offer it only to:

Goblin, ogre, owlbear, panther, eagle and maybe lizardfolk?

what about detect magic, DM?

Not warforged or skeleton either, because construct and undead.

dragons still drink. Everyone except skeleton and warforged.

Quote from MasterOfTheDungeons >>

I cast detect magic.

Also, it should be noted all the species drink water

Your detect magic reveals only that the water is vaguely magical, you don't detect any specific spells or areas of focussed magic.

Quote from LightningBoy831 >>

Stitch notices the newcomer, and decides that now has to be the time to pull off his new trick. (If he succeeds the acrobatics check) He suddenly runs towards the wall, and starts running along it. He then backflips off onto the floor, does a handspring towards the edge of the fountain, then dives over it, pulling the poles out of the kraken and the fish, spinning whilst doing so, then lands on the opposite wall, using his claws to keep himself on. “How y’a doing? The name’s Stitch, you are?” he then notices the tiefling and drops himself off the wall, landing in a Spider-Man pose. “What the heck is that thing?!”

Acrobatics: 19

Also, I think what I did is right, but I’m not sure. What I am thinking at the moment is that we get the water to go into all of the mouths (I expect by putting poles in all of them), then any that start overflowing we take the poles out, because ‘offer water to the thirsty’ might mean that the ones that overflow aren’t thirsty, as they seemingly have more water in them already, which is causing them to overflow.

Edit: I put the wrong modifier

Stitch starts running towards the wall, but the water slows his steps perhaps a smidge more than he had expected. He makes it onto the wall, and backflips off of it, landing with a large splash on the floor, and runs out of momentum on the way to the fountain. He manages to pull out the two poles, which are below the heads and are rather heavy, stopping the 2 water jets above them and causing the 5 remaining water jets to arc higher as the water pressure increases. You have run out of momentum entirely at this point, but still spin to face the newcomer, holding the 2 heavy metal poles and soaking wet.

(you rolled too well to fail utterly, but remember the room is at least a foot deep in water now!)

Quote from MasterOfTheDungeons >>

At least you're noticing how scary he is. I am going to remove the poles or whatever so all of the heads can drink.

You remove another pole from under the Lizardfolk, causing the water jets to arc even higher and into the water which is still slowly filling the room.

The current arrangement of water jets is that the Dragon, Owlbear, Panther and Eagle have water jets arcing over them, and the rest do not. The water in the room is definitely not going anywhere.

Another recap to save people from page hopping for answers, the heads are:

• goblin
• ogre
• owlbear
• panther
• fish
• magmin
• kraken
• dragon
• lizardfolk
• skeleton
• warforged

• eagle

I would say everyone but skeleton warforged magmin fish and kraken. If it still doesn’t work, take out dragon and lizardfolk

Magmin still drinks water.

I give up and cast misty step to get past the door

Quote from MasterOfTheDungeons >>

Magmin still drinks water.

I give up and cast misty step to get past the door

Alas, you cannot see past the door. You teleport directly into the door, appearing with your nose pressed against the wood. 

You notcie, from such close range, that someone seems to have scratched a line under one of the words in the phrase:

"To open this door, you need only offer water to the thirsty."

I drink some of the water

Quote from UndauntedDM >>

She’s Kayaws. I don’t think she’s intimidated by anything! :)

 Your right about that!

"We know that we have to have 7 poles in placed to make the water go into any of the heads. I agree with Harmony, i think we should take the poles that were under the fish and kraken and put them under the goblin and ogre." She motions to Stitch, who had pulled the poles out from under the fish and the kraken, "Toss me one." If Stitch gives her one, she will place it under whichever head (goblin or ogre) that Stitch doesn't put one under.

Alexander eyes the newcomer warily, but then cracks a smile after the scary teifling smacks into the door. Then he turns to watch what Kay is doing, nodding in approval. 

Hiding his smile, he tells the newcomer, "Unfortunately, the only way to get out is to solve the puzzles... Who knows how many more rooms like this we will have to get through." 

Quote from Rynn_Elocin >>

"We know that we have to have 7 poles in placed to make the water go into any of the heads. I agree with Harmony, i think we should take the poles that were under the fish and kraken and put them under the goblin and ogre." She motions to Stitch, who had pulled the poles out from under the fish and the kraken, "Toss me one." If Stitch gives her one, she will place it under whichever head (goblin or ogre) that Stitch doesn't put one under.

 Stitch tosses her one, then places the pole he still has under the goblin.

Quote from MasterOfTheDungeons >>

I drink some of the water

 You go to scoop up the water, but it somehow doesn't stay in your hands. You then stick your head into the pool and drink some - it tastes quite iron-y, very mineral-rich, and you are aware of a very unpleasant sensation as the water, which you now speculate to be enchanted to prevent it being contained, somehow trickles right through you as if you were made of gravel. 

Quote from LightningBoy831 >>

Quote from Rynn_Elocin >>

"We know that we have to have 7 poles in placed to make the water go into any of the heads. I agree with Harmony, i think we should take the poles that were under the fish and kraken and put them under the goblin and ogre." She motions to Stitch, who had pulled the poles out from under the fish and the kraken, "Toss me one." If Stitch gives her one, she will place it under whichever head (goblin or ogre) that Stitch doesn't put one under.

 Stitch tosses her one, then places the pole he still has under the goblin.

You both put a pole under the Goblin and the Ogre, and jets arc up, lessening the other 4 jets.

The water is now shooting towards the Ogre, Goblin, Dragon, Owlbear, Panther, and Eagle, and is splashing on their foreheads and running down into the pool, which is now around your knees.

Quote from MasterOfTheDungeons >>

I suddenly fall right in front of the fountain and say "Not again".

By the way I read the first 2 pages and then skipped here, so tell me if there is a bottomless pit right in front of the fountain or something.

I cast detect magic

EDIT: I am a winged tiefling who is kind of scary. I assume I fell asleep and woke up here?

EDIT: I notice everyone staring at the fountain and get 17 on perception

EDIT: Dark armor with fire and blade designs, also similiar to the Tiefling from Battle For Beyond episode 2, I got the idea for the race/picture from him.

Quote from MasterOfTheDungeons >>

what about detect magic, DM?

Could you please give me the results for this?

Also, what are the heads made of?

Quote from MasterOfTheDungeons >>

Quote from MasterOfTheDungeons >>

I suddenly fall right in front of the fountain and say "Not again".

By the way I read the first 2 pages and then skipped here, so tell me if there is a bottomless pit right in front of the fountain or something.

I cast detect magic

EDIT: I am a winged tiefling who is kind of scary. I assume I fell asleep and woke up here?

EDIT: I notice everyone staring at the fountain and get 17 on perception

EDIT: Dark armor with fire and blade designs, also similiar to the Tiefling from Battle For Beyond episode 2, I got the idea for the race/picture from him.

 

Quote from MasterOfTheDungeons >>

what about detect magic, DM?

Could you please give me the results for this?

Also, what are the heads made of?

Quote from ThorukDuckSlayer>>

Quote from MasterOfTheDungeons>>

I cast detect magic.

Also, it should be noted all the species drink water

Your detect magic reveals only that the water is vaguely magical, you don't detect any specific spells or areas of focussed magic.

The water is magical but not the statues?

Quote from MasterOfTheDungeons >>

The water is magical but not the statues?

Correct, and from your earlier exploit:

 You go to scoop up the water, but it somehow doesn't stay in your hands. You then stick your head into the pool and drink some - it tastes quite iron-y, very mineral-rich, and you are aware of a very unpleasant sensation as the water, which you now speculate to be enchanted to prevent it being contained, somehow trickles right through you as if you were made of gravel. 

You make the connection that the water has been enchanted such that it cannot be picked up or contained, such as by scooping it in your hands, filling a bucket, or in your case, drinking it!

but the statues can drink it?

Quote from MasterOfTheDungeons >>

but the statues can drink it?

That does appear to be the case, as when there were 7 jets going into the mouths of the creatures, the water seemed to be overflowing from some and not from others.