How to Make a Water Level. Water levels have been used for centuries. They're cheap, easy to make, very accurate and allow a person working alone to determine levels over large distances. By taking advantage of basic physics (the fact that water always seeks its own level), you can make a level that will be as accurate as anything you could buy.
Making a water level
Start with a plastic bucket and a length of clear plastic tube - 1/4 inch or 3/8 inch in diameter. The length of the tube itself doesn't matter, it just needs to long enough to reach to a fixed object. So, it can be as short as 5 feet or over 100 feet in length, (that's what makes water levels great for landscaping applications).
Drill a hole in the bucket a few inches up from the bottom (make the hole slightly smaller than the diameter of the plastic tube).
Slice an end of the tubing lengthwise for a couple of inches and remove one side of the sliced tubing.
Insert the sliced end into the hole in the bucket and pull it tightly into the hole (it needs to be watertight).
Pull from the inside and force the uncut tubing into the hole.
Using a water level
A water level works because the water level in the bucket and the water level in the tube will be exactly the same. So, when you hold the tube against fixed objects and mark the water level on each, the marks will be level with each other. Here's how to use it in a landscaping application.
Drive a stake into the ground at one side of the area you want to level, then drive a second stake into the ground on the other side of the area.
Place the bucket on a stool or even an overturned box and fill it with water.
Allow some water to flow freely out of the plastic tubing until all bubbles are out of the tube and then close the end of the tube.
Pick up the end of the tube, hold it up to the top of one of the stakes and mark the stake beside the water line in the tube.
Carry the end of the tube over to the other stake, hold it to the top and mark this stake where the water line is in the tube. The marks on the two stakes will be exactly even with each other.
Using these two marks as a common base (since they are level with each other), you can make sure anything you build will be level. By simply measuring equally (up or down) on both stakes, you can build to any height and know that you are still level.