I'm using one as we speak, I germed the seed and put it in, I have the water going around it constantly, but it just drains back out and in again through the cycle, the seeds to small I've found I need to manually water it.
but yeah back to the constant water flow, it's not going to drown the seed, they still sell hydroponics because they work. To my little experience and larger knowledge they do their job well, so no worries.
at first the root system isnt big enough to reach where the waters dropping, usually with hydro you would get a clone, im trying with a seed to see if I can. get a water sprayer, I Bought one from Canadian tire and just spray 25% of it in the area twice a day - fill it up twice a day* 90% of the water drains back into the resevoiar anyways.
the medium doesn't hold water anywhere near as well as soil thats one of the reasons for the constant dribbling of water, you CANT over water with hydroponics.