Aquaponics Growbed Drain

This little gizmo serves as two drains in one.  The first drain is an adjustable ‘slow’ drain.  It will need to slowly drain about 75 gallons of water over a 30 minute period.  The second drain is an overflow, and has to be big enough to take away all the water my pump can throw at it.  I didn’t bother to try to calculate the flows and hole sizes and pipe sizes, all trial and error for me!  I wound up making a huge mess of my work area after I used the saw, drill, and grinder on these little parts.  I started with a 1-1/2″ PVC to 1″ female NPT adapter, attached to a 1″ close nipple.  I ground down the OD of the fitting so the 1-1/2″ coupler fits on it loosely, and can be easily turned.  The turning action is how I’ll adjust the size of the ‘slow’ drain.  If the holes are all lined up, I’ll have (2) 1/4″ holes.  I can twist the coupler to make the holes smaller.  The large 4″ pipe fits over the whole drain to provide air space to prevent roots from growing into the drain and clogging it up.

twist coupler to change hole size

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