Union Fitting

A union fitting consists of three parts: two threaded ends (male or female) and a separable nut that clamps them together. One end screws onto a pipe or fitting permanently; the other end sits loose under the nut until tightened, allowing you to break the joint later without unthreading the connected pipes.

Unions save time and frustration when you need to service equipment, replace sections, or work around tight spaces where you can't get a wrench on both sides. They're standard where isolation is expected—under water heaters, on the inlet side of pumps, at hose bibs, and anywhere maintenance access matters.

Brass unions work for most potable water; dielectric unions prevent galvanic corrosion between different metals. Confirm the thread size and pitch match your pipe, and always use a backup wrench on the fitting body while tightening the nut, or you'll spin the whole assembly and waste time.