Terms & Definitions

Gallons per Miniute: Amount of liquid flow in a system - Not how fast it is moving through a pipe.

Velocity: Speed of flow through a pipe system - Not how much is moving through the pipe

Minimum Velocity: (Scouring Velocity) 2 feet per second is required to keep solids suspended or from settling inside the pipe.

Maximum Velocity: Velocity greater than 10 feet per second will damage piping systems, valves, etc.

Static Head: Total distance in elevation from the low water line (Off float level) inside the basin to the point of discharge (Vertical distance)

Friction Loss: Any additional head created by the resistance within the piping system due to pipe length, fittings and flow rate.

Sewer Back Pressure: (1 PSI = 2.31 feet of head) Due to multiple pump systems...i.e. pumping into a grinder loop or the bottom of manhole.

Total Dynamic Head: Static Head (constant) + Developed Head (changes in flow rate) = TDH

Shut Off Head: The point at which the pump will no longer provide any flow. This is shown as the furthest point on the left hand side of the pumps performance curve.

Types of Pump
Sump Pump: pump to handle water that does not drain by gravity. ie. basement sumps, car parks, rainwater harvesting, manholes and low land areas.

Effluent Pump: pump for grey, soiled water, ie from septic tanks. upto 3/4" inch.

Sewage Pump: pump to handle waste from homes, offices and anywhere with W/C facilities. They are not grinder pumps and should not be used for commercial applications. will not handle sanitary products and products inc nappies, napkins etc.

Pump Sizing

Pump Lift: The vertical lift (dynamic head) it has to pump. measured from the outet of the pump to its highest pumping within the discharge pipe.

Horizontal Run: distance slows down the liquid within the pump and horizontal run needs to be considered when calculating the overall pump performance.

Pipe Size: The pump discharge size will determine the pipe size. Using pipe that is smaller than the pump discharge will cause friction loss and more back pressure on the pump affecting its performance.

GPM: (Gallons Per Minure) Determine how many gallons per minute the pump needs to remove. undersizing the pumps basin will cuase the pump to run more frequent affecting the lifespan of the pump.

Guide To Sizing A System

1. Determine the application the pump is required to do: sump, effluent or sewage.
2. Determine voltage of electrical supply for pump.
3. Determine the approx GPM of flow into system using velocity load, velocity is determined with a minimum of 2ft per second flow in order to keep pipeline free. The following is recommended for use.
pipe size 1.5" - 13GPM
pipe size 2" - 21GPM

System Load Sizing (as a general rule)

Sump systems: Calulate basement square footage, divide by 100 and then multiplied by 2.50 will equate the GPM (i.e 500 sq.ft basement will equate to 12.5 GPM)

Sewage systems You must add total fixtures (e.g taps, w/c, bath, shower, washine machine etc) that will drain to the system. Each unit has a value (see table below)

Add all fixtures values together and multiply by 0.5 to get an estimated GPM load (e.g 45 fixtures x 0.5 = 22.5 GPM). The GPM rate needs to be greater than the required velocity in order to keep the pipe free of debris.

Value table
Bath = 2
Dishwasher = 2
Kitchen Sink = 2
W/C = 2
Shower = 2
Unlisted 1.5" pipe = +3
Unlisted 2" pipe = +4