On the Level

By William T. Cox Jr.

Since ancient times builders have devised several types of tools, collectively called levels, for aligning structures relative to the horizon. Gravity's effects on weights and water are the two time-honored ways to sense horizontal, but the measuring instrument industry is still coming up with new methods. Here's just a sampling of levels simple and sophisticated, and how you can put them to work in an old house.

Water level
One of the first levels I ever used was a water level simply a 50'-long, clear vinyl 3/8 tube filled with colored water (see drawing at right). It takes two people to operate. The tubing should have been larger to allow the water to settle more quickly, but the price of clear tubing was astronomical back in the 1970s. Today, the stuff costs around $1 a foot, which still isn't cheap.

The water level is a visual reference device; the water is either on the mark, or it is not. The sole trick to using a water level is always reading the level at the cup of the water instead of at the curved upper lip, or meniscus. Due to the way the water adheres to the inside of the tube, the meniscus varies too much to be reliable. Even so, I've read that a water level is accurate to 1/16, depending on the skill of the people using it.

To use a water level to level a line around a kitchen for, say, installing a chair rail, have a partner hold one end of the hose on the wall with the water mark at the desired rail height. Then you can take the other end and simply mark off the wall every few feet by raising or lowering the hose until the water is on the mark. The beauty of the water level is that it works just as well if the ends are many feet apart or even separated by obstructions, such as a wall between two rooms. (Keep in mind that a chalk line will sag no matter how tight you pull the line; gravity is always at work.)

Flying by instruments
Unlike a water level, a spirit level uses a bubble of air floating in a carefully calibrated vial to sense horizontal. Spirit levels range from hand-sized tools (such as bull's-eye, line, and torpedo levels), through 18 and 24, up to 6' long and more. A 48 spirit level fresh out of its packing sleeve should be accurate to the thickness of a crisp $100 bill, but even this precision is enough to throw a layout way off if, say, you want to level a line around a 11' x 15' kitchen. Luckily you can compensate for any error by using yet another trick. If you want to use that new 48 spirit level for your kitchen chair rail, each time you draw a line flip the level end over end as you move around the room. This way you reverse any small errors in the level so, in theory, they will cancel each other out. Even so, you may miss your starting point by as much as 1 over the distance around the room.

Here's how to check the level to see if it is accurate. Place the instrument on a flat wall and angle the tool until the bubble reads level. Next, draw a line under or over the level. Then, rotate the level 180 degrees, making sure it returns to the mark you just made. If the bubble still reads horizontal, the level is accurate.



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