I stumble upon of poultry watering nipples on eBay, and bought a few. I found some leftover sewer pipe, and a closure piece for it. Enough to start with.
I put them together quickly (jah - had some wrestling with that bend piece).

Step 1: Materials

Materials:

- 160 mm diameter sewing pipe. Its length isn't important. Choose the length what fits your chicken coop, chicken tractor, etc.
- Closure piece for the sewing pipe. Matching size and type of your pipe
- Bend piece for the sewing pipe. Matching size and type of your pipe. It have to be between 90° and 67°. If it less, then the water will come out, and you can't take advantage of the capacity of the pipe.
- Poultry watering nipples. At least a few what you need. The longer pipe you have, the more nipples you need.
- Drill bits. A smaller one for pre-drilling, and a bigger one what matches for the nipples
- Measuring tools, and pencil or marker
- Saw. A jigsaw machine is better.
- A little piece of sandpaper
- Another materials for hanging it onto its place

Step 2: Measuring

At first you have to determine the location of the holes. (Precondition: pipe, closure and bend pieces put together.)

Lay the pipe on its side. Make sure that side of bend piece is on same plane as pipe is. I've used little piece of slats.
Find the middle line of the pipe (what is the lowest line on it), and mark it.

Divide it into equal parts for available nipples, and mark the drilling points across the middle line.

Step 3: Drilling

Fix the pipe for the drilling.

Choose the smaller drill bit for pre-drilling. Make the holes on the marked points.
Change for the bigger drill bit and finish the holes.

I've used 3 mm and 8 mm diameter bits. Unfortunately I couldn't put in the nipples, so I re-drill the holes with 8.5 mm diamater, then with 9 mm diameter bits. The last one did the job and fits better for the nipples.

Step 4: Final Steps

Screw in the nipples to the holes. You can use sealant to avoid leaking.

Prepare the final place of the pipe. Make sure that the whole watering pipe is fastened to its place securely and in leveled way.
Choose the height of nipples from ground between 35 - 45 cm, depending of the size of your poultry.

Please note that 1 meter long pipe can contain 20 liters of water, so it can weight over 20 kg! On the other hand it can provide water for longer period.

Choose smaller diameter pipe If you need longer version of this watering system. This can reduce its weight.

You can put a cup on the bend piece to avoid pollution.