At some time or another, you’re going to need a level to determine horizontal or vertical planes, and naturally, different jobs require different tools.
A standard carpenter’s spirit level will do for most jobs. Start with a 24″ or 30″ level, or a 4-footer if you’re doing a lot of framing or leveling bricks or concrete blocks. (Where available, good solid wood stands up to rough treatment better than metal.) And if you’re into high-tech, you can even find fancy electronic levels.
But if you need to check level beyond eight feet (decks, driveways, floors, ceilings), you need something more.
There’s the inexpensive line level, a small spirit level you attach to mason’s line, there are laser levels, and there are transits and builder’s levels, which are expensive, delicate pieces of equipment.
But a simple water level is cheap, effective, and can do things expensive equipment can’t, like confirm level around obstructions.
You can get a manufactured one or make a one-person level with a bucket for a reservoir, but if you have a helper, the most basic method works great.
Just buy a long length of 5/16″ clear plastic hose, fill it with water (food color makes it easier to see), shake out any air bubbles, and hold up the two ends. Due to the amazing properties of physics (or something like that), the water level is the same. (Continue shaking air bubbles out until it is.) Then, no matter where you position the ends of the hose (being careful not to kink it or lose water) the level at each end is the same. To adjust to match a reference point, just raise or lower one end of the hose.