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Pitot Static Systems
by Evan McCombs

Years ago when homebuilding first started, static systems were rarely installed.  Open cockpit sport planes only used an airspeed and altimeter and indicated airspeed was not counted on to be accurate.
With our modern homebuilts, enclosed cockpits and modern radio equipment, transponders and encoding altimeters, we need a reliable source of static air, without pressure or vacuum.  This will give us accurate airspeed, altitude and vertical speed indications.

Figure 1 shows a typical Pitot Static system.  This figure also shows a moisture trap and drain plug. 

You can also see a very handy addition.  This is a tee that is added to the main static line which is located in an easy place to get to.   This tee has a plug which is removable to facilitate the connection of a static vacuum pump.  The static ports may then be taped over and the static system can easily be tested to comply with FAR 43 Appendix E.
Later model, certificated airplanes have a static sump to collect moisture which may collect in the static system after a rain storm or heavy dew.  So, water can then drain back out of the system.

Editor Note:  Apologize for scanner quality on drawing--just couldn't get any better.