How to Choose the Right Drain Jetter: Pressure, Flow Rate and Nozzle Selection Explained
Most buyers shopping for a drain jetter look at psi and stop there. On its own, pressure says almost nothing about how fast or effectively you clear a line. The number that counts is pressure multiplied by flow, and in Australia that same figure decides which safety class your machine falls into under AS/NZS 4233.1:2013.
Here is what pressure and flow do inside a pipe, how to size a unit to the diameters you work with, and how to pick nozzles for grease, roots and scale.
Pressure cuts, flow carries
A drain jetter is rated by pressure, in bar or psi, and flow, in litres per minute. Pressure breaks the blockage apart. Flow carries the debris back down the line and out through the manhole. Multiply the two and you get real cleaning power, which is why a 200 bar unit at 60 L/min out-cleans a 350 bar unit at 15 L/min on most sewer work.
Get that balance wrong and you spend the afternoon cutting a neat hole through a grease plug, then watch the line pack up behind you.
That multiplication matters legally too. AS/NZS 4233.1:2013 classifies jetting systems by bar litres per minute: 800 to 5600 is Class A, above 5600 is Class B. A 200 bar machine at 20 L/min comes to 4,000, so every unit you would buy for sewer work sits inside that standard. Worth knowing before you put a new operator on the reel.
Match the drain jetter to the pipe you actually work in
On DN100 house drains and laterals you need enough pressure to cut, moderate flow, and a nozzle small enough to get through bends and a trap. The FlexJET hydro jetter is built for that work, rated from OD 40 mm to OD 300 mm, supplied with electric start, sewer nozzle, hose and a four channel radio remote, and mountable in a van, trailer or flatbed.
On DN150 to DN300 mains, flow becomes the limiting factor. Sand, grit and silt have weight, and it takes volume to move them uphill to the next manhole.
The common mistake is over specifying pressure and under specifying flow, then finding the tank empty twenty minutes in. Ask what it holds and how long the unit runs flat out before a refill.
Nozzle selection: grease, roots and scale are three different jobs
The nozzle is the cheapest part of the kit and the biggest variable on the day.
1. Grease and fat
Use a rotating or turbo nozzle. The spinning jets scour the full circumference instead of cutting a slot through the middle of the plug. They earn their keep in 50 mm to 100 mm lines under food premises and apartment stacks.
2. Roots
A forward jet to penetrate, rear jets to flush what comes loose. Be realistic here. A jetter strips fine root hair, but on a mature root mass in old vitrified clay, mechanical cutting is the honest answer. Run a robotic cutter through first, then jet out the cuttings.
3. Scale, sand and silt
Rear jets only, no forward jet, so all the energy goes into thrust and wall scour. Jet angle is the dial. Around 15 degrees gives maximum pull for long runs and uphill work, while 30 degrees trades thrust for contact on the pipe wall. Dual angle nozzles combine both, which is why they suit municipal runs.
Size the nozzle to the pump, not to the blockage
If the orifice is too large, flow exceeds what the pump can deliver and operating pressure drops away. Too small, and you throttle the flow, load the pump and lose the carrying capacity that moves debris out of the line. Every reputable nozzle maker publishes a chart matching orifice size to flow and pressure. Use it. For sewer work, size for the most flow the pump will give you. A nozzle chosen like a pressure washer tip is almost always too tight.
Two things people forget. Hose diameter and length both cost pressure at the nozzle, so 60 m of 13 mm hose beats the same run in 10 mm. And check the nozzle’s own rating: plenty of stainless sewer nozzles top out at 250 bar.
What to ask before you pay
Ask who services the unit and where, whether nozzles and pump parts are held in Australia, and what training comes with it. Downtime costs more in a fortnight than the price gap between two machines.
Austeck has supplied pipeline equipment from Alexandria in Sydney since 1992, to customers including Sydney Water, Watercare and Veolia across Australia and New Zealand. The after sales service and support is the part customers mention most. Pairing a jetter with a drain camera also lets you prove the line is clean, which turns a clearing job into a reported one.
Frequently asked questions
What psi does a drain jetter need for a blocked sewer?
For DN100 sewer and stormwater lines, most Australian operators run a drain jetter between 150 and 250 bar, roughly 2,200 to 3,600 psi, at 15 to 40 L/min. Pressure breaks the blockage, flow removes it, so read both figures rather than buying on psi alone.
How many litres per minute do I need?
Flow scales with pipe diameter. Around 15 to 25 L/min suits 40 mm to 100 mm drains, while DN150 to DN300 mains want 40 L/min or more to shift sand and silt. Under supplying flow is the most common reason a cleared line blocks again in weeks.
Will a jetter clear tree roots on its own?
A jetter cuts fine roots and flushes the debris out, and handles regrowth well on a maintenance cycle. Established root masses in vitrified clay need a mechanical or robotic cutter first, with the jetter used afterwards to clear cuttings.
Getting the spec right
Before you ring anyone, write down three things: the pipe diameters you work in most weeks, your typical run length from access to blockage, and the blockage you strike most often. Those three decide pressure, flow, hose length and nozzle set, in that order.
Then talk it through with someone who sells the gear and services it. Free call Austeck on 1800 287 835, or contact us for pricing on a drain jetter matched to the work you actually do.