No, you don't put Valbazen in the waterer.
You give it orally to each chicken one at a time.. avoid the windpipe.. give 1/2 cc/ml per standard chicken and 1/4 cc/ml per bantam or small chicken. Repeat in 10 days... withhold eggs.... do not eat eggs until 15th day AFTER the last dose. Watch poop, if there are tapeworms, tapeworm segments it will most likely take more than two doses to get them treated.
Use the Search here on BYC for "worming with Valbazen".... with dawg53 as reliable info.
I do not know about ducks at all... I would assume they also get worms... Valbazen is not for chickens either, we use it "off label" for chicken worming. You would have to ask someone who knows ducks... or ask in the duck topic about worming ducks with Valbazen. Maybe a search "worming ducks with Valbazen".
Good luck.. (if you put it in the water, you will not know who got what, who got enough or who got too much... it is not a good and reliable way to worm a flock).