| Scenario | Filter Type | Water Quality | Effective Area | Loading Rate | Max dP | Recommended Capacity |
|---|---|---|---|---|---|---|
| Drip zone on clean water | Screen | Clean | 0.0800 m^2 | 18.0 m^3/m^2/hr | 35 kPa | ~22.8 L/min |
| Organic debris from pond | Disc | Moderate | 0.0800 m^2 | 15.0 m^3/m^2/hr | 35 kPa | ~16.0 L/min |
| High solids, needs backwash | Media | Dirty | 0.0707 m^2 | 10.0 m^3/m^2/hr | 35 kPa | ~7.7 L/min |
| Fine filtration for tanks | Cartridge | Moderate | 0.0600 m^2 | 8.0 m^3/m^2/hr | 35 kPa | ~6.4 L/min |
- Flux limit: Q_flux = A x L x D
- Pressure-drop limit: dP = K x Q^2, so Q_dP = sqrt(dP_max / K)
- Recommended: Q_rec = min(Q_flux, Q_dP)
- Select units, then choose a filter type that matches debris.
- Pick an area method and enter the best available dimensions.
- Set water quality to apply a conservative derating factor.
- Enter loading rate from guidance or manufacturer recommendations.
- Enter allowable pressure drop and a reasonable headloss coefficient.
- Press Calculate, then review which constraint limits capacity.
- Download CSV or PDF to document selections and maintenance plans.
What capacity should I target for drip irrigation?
Start with the recommended capacity, then confirm it meets the combined zone flow at your operating pressure. If multiple zones can run together, size for the maximum simultaneous flow and include a safety margin for fouling.
How do I choose a loading rate value?
Use manufacturer guidance when available. For unknown sources, pick a conservative rate and adjust after monitoring cleaning frequency. Dirtier water, algae, or organic debris should use lower rates to keep headloss stable.
What does the headloss coefficient K represent?
K summarizes how quickly pressure drop rises with flow for a given filter and piping condition. Higher K means the filter reaches the allowable pressure drop at a lower flow, so the pressure-drop limit will govern sooner.
Why does water quality reduce capacity?
Suspended solids block pores and shrink effective open area. The derating factor lowers sustainable flow so the result better matches field performance and typical cleaning intervals rather than clean-water test conditions.
When should I enter screen dimensions instead of area?
Use dimensions when you do not know the rated filtration area. The calculator estimates cylindrical area and applies open-area fraction. If you have the manufacturer’s effective area, direct entry is usually more accurate.
How can I reduce high pipe velocity warnings?
Increase pipe diameter, shorten runs, remove restrictive fittings, or split flow across parallel lines. Lower velocity reduces friction loss and water hammer risk, improving stability at emitters and protecting filter seals.
Purpose of flow capacity sizing
Filter flow capacity defines how much water can pass while protecting emitters and maintaining stable pressure. Oversizing wastes cost and footprint, while undersizing raises headloss, shortens cleaning intervals, and risks uneven irrigation. This calculator converts your area, loading rate, and allowable pressure drop into a practical recommended capacity for garden systems, from drip zones to small recirculating ponds.
Inputs that drive capacity
Start with filter type and water quality. Screen and disc units suit moderate solids, while media tanks tolerate heavier loads through backwashing. Cartridge options deliver fine clarity but clog faster. Effective filtration area can be entered directly or estimated from screen dimensions or tank diameter. Water quality applies a derating factor so capacity reflects real clogging behavior, not clean laboratory conditions.
Loading rate and flux control
Loading rate, sometimes called flux, links area to sustainable flow. The calculator computes Qflux = A × L × D, where A is effective area, L is the chosen loading rate, and D is the quality derate. When Qflux governs, capacity is limited by surface loading, so increasing area, improving pre-screening, or reducing flow improves reliability and reduces cleaning frequency.
Pressure drop limit and headloss
Pressure drop is modeled with a simplified quadratic relation, dP = K × Q². Your allowable dP and headloss coefficient K produce QdP = √(dPmax/K). When the pressure limit governs, reducing fittings, choosing a lower-resistance filter, or upsizing the body helps maintain operating pressure across valves, emitters, and laterals, especially during peak demand.
Using results for operations
The recommended capacity is the smaller of the flux and pressure limits, reported in L/min, m3/hr, and gpm. Use the pipe velocity check to avoid excessive speed that amplifies friction and water hammer. The optional turnover time supports ponds and tanks, helping you set circulation targets, plan bypass options, and schedule cleaning and recordkeeping with consistent intervals. Save CSV or PDF outputs to document assumptions and compare seasonal water changes and maintenance needs over time.
What capacity should I target for drip irrigation?
Start with the recommended capacity, then confirm it meets the combined zone flow at your operating pressure. If multiple zones can run together, size for the maximum simultaneous flow and include a safety margin for fouling.
How do I choose a loading rate value?
Use manufacturer guidance when available. For unknown sources, pick a conservative rate and adjust after monitoring cleaning frequency. Dirtier water, algae, or organic debris should use lower rates to keep headloss stable.
What does the headloss coefficient K represent?
K summarizes how quickly pressure drop rises with flow for a given filter and piping condition. Higher K means the filter reaches the allowable pressure drop at a lower flow, so the pressure-drop limit will govern sooner.
Why does water quality reduce capacity?
Suspended solids block pores and shrink effective open area. The derating factor lowers sustainable flow so the result better matches field performance and typical cleaning intervals rather than clean-water test conditions.
When should I enter screen dimensions instead of area?
Use dimensions when you do not know the rated filtration area. The calculator estimates cylindrical area and applies open-area fraction. If you have the manufacturer’s effective area, direct entry is usually more accurate.
How can I reduce high pipe velocity warnings?
Increase pipe diameter, shorten runs, remove restrictive fittings, or split flow across parallel lines. Lower velocity reduces friction loss and water hammer risk, improving stability at emitters and protecting filter seals.