|DESIGN CALCULATION GUIDE FOR DRIP SYSTEMS
STEP 1:           Calculate the design flow. Example:
Flow = 150 GPD PER BED x 3 Bedrooms = 450 Gallons Design Flow
STEP 2:           Determine the soil loading rate.
A field evaluation of the soils at the site must be completed by a qualified person. See loading rates for your jurisdiction. Loading rates should be which stated in gallons per day per square foot of total dispersal area. In the event the gallons per day per square foot are listed as bottom area loading rates, divide the number by 3.
STEP 3:           Compute total tubing necessary for the absorption field.
From Area chart:
Tubing Necessary = Dispersal Area / 2 = (Daily Flow Area Loading Rate) / 2 = Linear Feet
Tubing Necessary = (450 GPD / 0.1 Gal/Day/Sq.Ft.) / 2 = 4,500 Sq.Ft / 2 = 2,250 Linear Feet
STEP 4:           Determine layout and shape of the dripper line absorption field.
Keep each individual dripper line lateral length no greater than 300 feet from its connection to the supply manifold to its connection to the return flush manifold because of excessive friction loss. Always configure the system supply line to feed laterals at the lower end of the dripper lateral lines and return from the highest elevations. When running a continuous dripper line, it may turn and make a loop or series of loops back to the return flush line before making a connection. Keep each lateral in a zone close to the same length. The zone detail table below is a useful guide to standard details.
ZONE DETAIL TABLE
STEP 5:           Calculate pump head loss.
Calculate the head loss to prove standard pump is adequate. The head loss must be calculate for three conditions, dosing, field flushing, and filter cleaning.
Head Loss During Absorbtion Field Dosing
The flow rate during absorption field dosing depends on the amount of dripper line required for any particular installation. The flow rates are easily calculated as follows:
Note:           GPH = Gallons Per Hour           GPM = Gallons Per Minute
Dripper Line Length in Absorption Field / 2 Ft Emitter Spacing = Number of Emitters
Number of Emitters x .65 GPH = Absorption Field Dosing Rate in GPH
GPH / 60 Minutes = Absorption Field Dosing Rate in GPM
Calculate the head loss for this condition for all components using standard head loss methods and add them together. Compare to pump output capacity for to confirm proper selection.
Note the head loss through the tubing is based on the flow rate at the length of lateral. This information and the Head loss through the filter unit should be provided by the manufacturer.
Head Loss During Field Flushing Flow Rates
Since automatic flushing of the dripper lines in the absorption field is an integral function of the total system, it should be considered as part of the overall flow rate generated by the system. It has been established that proper scouring and flushing of any pipe system will require at least 1.6 gallons per minute (GPM) flow at the outflow end (distal end) of any pipe. Therefore, we should design for a flow of at least 1.6 GPM out of each dripper line connection that has been made to the return flush manifold pipe. Multiply each return manifold connection by 1.6 GPM to get the field flushing flow requirement. Add this flow rate to the dosing flow and calculate the head loss for this condition for all components using standard head loss methods and add them together. Compare to pump output capacity for to confirm proper selection. Note the head loss through the tubing is based on the flow rate at the length of lateral. This information and the Head loss through the filter unit should be provided by the manufacturer.