Chickens do not have nipples, only mammals do.
And they contain milk, not water.
And you cannot post of them on arfcom

And I want to hear more because I am wondering if this is a more logical way to go for water than my 1 gallon waterer in the coop - my coop is only 3'x4', and I have 4 birds. The hanging waterer takes up too much space in the winter.

What do you feed your waterer with?

Try flushing the lines with PW-water treatment or citric acid to break up the mineral build up in the nipples.
I own a large scale poultry farm and have to run PWT thru the lines and nipples every few days.

Mine never worked correctly either.  They always leaked and made horrible mess..Waste of money.  I currently use a 2 gallon heated dog dish.  It works great all year and much cheaper than the actual chicken waterer and heater.

I use about a dozen of them and have zero leaks... even after a few hard winters and numerous hard freezes and me knocking them around to free the ice.  

First check to confirm they are leaking from the metal post and not from the threads.  If it's threads, then re-thread them with a bit of silicone to seal up.  

There are cheap ones out there... they are noticeably smaller in comparison to the better ones.  I ended up with a few of each somehow... but even the cheapos haven't been leaking for me (knock on wood), though I mostly use those in a brooder.  Check to make sure the bearing moves freely, and if yours has two different size metal posts, try the heavier post on top - this should help to seat the bearing tighter when closed.  Worst case, buy some better ones... I'll never go back to any kind of open watering again.

We have a lot of minerals in our water here but I've not yet had a problem with it affecting the nipples.

The poultry nipples I've used are quite simple affairs... just a bearing captured between two metal pins.  No springs, washers etc.  Not much to go wrong or wear giving the forces as play.  The bird pecking the exposed pin unseats the bearing a bit and the upper pin acts as the counter force to insure it re-seats.  I have heard of some folks who used them in narrow dimension PVC pipes running horizontally that there wasn't enough of a water column above the nipple to get them to seal properly.  I've only used them in buckets, but I've never had a problem with them leaking even when the bucket was near empty (thus having a similar minimal water column).

I had a set that leaked because they were at a bit of an angle. To fix the leak I pulled them apart and drilled the plastic section that is screws into the water container a touch larger. I forget what sized bit that was. Maybe 9/64"?  If I recall I was the next size up from 1/8'in my DeWalt bit set. Anyways, the larger hole made all the difference. YMMV.

Filter your water???

I've got 2 setups with a 5 gallon bucket feeding 1" pvc pipe with 7 or 8 nipple on bottom of pipe. Sometimes dirt or algae can stop the nipple from closing properly. I just tap each one a couple times to clear debris when I fill the water bucket. Excellent product. Water stays clean and I only have to fill the buckets twice a week.

I had the same issues with one of my 5g buckets. They will drip until the bucket only has a half gallon of water left. With it being unreliable, I pulled them. I had to go back to my steel cans. With 110+ deg heat, I have to know there is 20 gallons of water in the coup. I pulled the nipples and washed them, soaked them in vinigar, and reinstalled. It didn't help.

I had the same issue with drinker cups installed into 5g buckets. They would just drain out till the bucket was near empty. The hatchery I bought them from said I "modified" them when I sent them back. I said bullshit and I only opened them to clean and reinstalled them attempting to get them to work properly. Didn't make a difference and they insisted I ruined them by modification... I didn't. I won't be buying from Meyer hatchery again, and have moved my business to Cackle Hatchery.

Mine worked fine no issues with dripping.