BMED

Trap Gully Basin

Prevents sewer gases from entering a building while collecting wastewater.

Grease Trap

Separates grease and oil from wastewater.

Manhole / Inspection Chamber

An access point used for inspecting and cleaning drains.

Septic Tank

A tank that settles and partially treats sewage.

Absorption Pit

A structure that allows effluent to soak into the soil.

Soakaway

Disposes of wastewater by ground percolation.

Tile Field

Spreads effluent through perforated pipes in the soil.

Evaporation / Reed Bed

Uses plants and evaporation to treat wastewater.

Ellipse

A closed curve in which the sum of the distances from two fixed points (foci) to any point on the curve is constant.

Parabola

An open curve formed by a point moving so that its distance from a fixed point (focus) equals its distance from a fixed straight line (directrix).

Hyperbola

An open curve with two branches in which the difference of the distances from two fixed points (foci) is constant.

Cycloid

A curve traced by a point on the circumference of a circle rolling on a straight line.

Inferior trochoid

A curve traced by a point inside a circle as the circle rolls along a straight line.

Superior trochoid

A curve traced by a point outside a circle as the circle rolls along a straight line.

Involute

A curve generated by a point on a taut string as it unwraps from a circle.

Archimedean spiral

A curve in which the distance from the centre increases uniformly with each turn.

Centroid formula

(A1/A) × d

2nd moment of area

A2 ×d²