Drip Flushing & Run It Till It's Clear
Flushes sediment
Enter your lateral diameter and number of laterals to get the flush flow per lateral, the total flush flow and the water used to flush at the clearing velocity.
Set your flush parameters
Next: flush in batches so each open lateral keeps ≥ 0.5 m/s; your total demand is 1 L/s — confirm the pump and submain can deliver it.
Keep flush velocity ≥ 0.5 m/s to carry out sediment. Flow = velocity × pipe cross-section; opening too many ends at once drops velocity below scour.
Drip flushing — key facts
- Scouring velocity
- ≥ 0.5 m/s (≈30 m/min)
- Flow per lateral
- velocity × pipe area
- 16 mm lateral
- ≈ 6 L/min at 0.5 m/s
- Total flush flow
- flow × laterals opened
- Flush volume
- total flow × flush time
- Goal
- run until water runs clear
- Pairs with
- filtration + acid/chlorine
- Privacy
- Runs in your browser; nothing uploaded
Open the ends and let it run clear
No filter is perfect. Fine sediment, biofilm and mineral precipitates slip through and travel to the dead ends of your drip laterals, where they settle and slowly choke the last emitters. The fix is simple and physical: open the lateral ends and let water run until it comes out clear — but only if the flow is fast enough. Below about 0.5 m/s the debris just sits there; at the scouring velocity it lifts and washes out.
This tool computes the flush flow per lateral, the total flush flow for the laterals you open at once, and the water used over your flush time. Use it to size the flush manifold and confirm your pump can hit the scouring velocity. Pair it with the Drip System Flow, Drip Chlorination and Drip Lateral Length tools to keep the whole system clean and uniform.
Hit the scouring velocity
0.5 m/s is what actually lifts sediment out.
Size the flush manifold
Total flow tells you the sub-main and valve size.
Don't open too many
Too many ends at once drops velocity below scouring.
Budget the water
Flush volume shows exactly how much you'll use.
Frequently Asked Questions
Why do drip laterals need flushing?+
Even with filtration, fine sediment, biofilm and precipitates settle and travel to the dead ends of drip laterals, where they accumulate and eventually block emitters. Periodic flushing — opening the lateral ends and letting water run until it comes out clear — sweeps this debris out before it clogs the line, keeping uniformity and emitter flow steady through the season.
What flush velocity should I aim for?+
The accepted target is a scouring velocity of at least 0.5 m/s (about 30 m/min) at the open lateral end. Below this, sediment isn't carried out; at 0.5 m/s or more the flow lifts and removes settled particles. The flush flow per lateral is this velocity times the cross-sectional area of the lateral, which this tool computes for your pipe diameter.
How is the flush flow per lateral calculated?+
Flush flow = velocity × cross-sectional area of the lateral. For a 16 mm lateral the inside area is about 0.0002 m²; at 0.5 m/s that's roughly 0.0001 m³/s ≈ 0.36 m³/h ≈ 6 L/min per lateral. Multiply by the number of laterals you open at once to get the total flow your manifold and pump must deliver.
How much water does flushing use?+
Flush volume = total flush flow × the time you run the flush. You only need to run until the water at the ends runs clear — often one to a few minutes per lateral group. The tool gives the flush volume so you can budget the water and avoid wasting it, and shows how flushing more laterals at once raises the instantaneous flow.
How many laterals should I flush at once?+
Flush in groups small enough that you can still hit 0.5 m/s in each open lateral given your available pump flow. If you open too many ends at once the velocity drops below scouring and nothing is cleaned. The tool's total flush flow tells you what your pump must supply for the group size you choose.
How often should drip laterals be flushed?+
Flush at the start and end of every season, and during the season whenever you see flow falling or after heavy sediment loads. Lines on surface or river water need flushing more often than those on clean well water. Combine flushing with periodic acid and chlorine treatment for full preventive maintenance.
What is a flush manifold?+
A flush manifold is a sub-main connecting the dead ends of several laterals to a single flush valve, so you can flush a whole block by opening one valve instead of every lateral end by hand. Size it for the total flush flow of the laterals it serves — this tool's total flow output is exactly that sizing figure.
Does flushing replace filtration and chemical treatment?+
No — they work together. Filtration keeps coarse particles out, chemical treatment (acid for scale, chlorine for biofilm) dissolves what filtration misses, and flushing physically removes the settled residue. Skipping flushing lets fine sediment build at the ends regardless of how good your filter is.
Are these figures exact?+
They're solid planning estimates from velocity × area and your inputs. Real lateral inside diameters vary by wall thickness and manufacturer, and field velocity depends on supply pressure and how many ends are open. Use the tool to size the manifold and pump, then confirm by checking that the end discharge actually runs clear.