By reaction. The rearward jets push water backwards, and the equal and opposite force pulls the hose forward - the same principle that moves a rocket.

A jetting nozzle has a ring of jets angled backwards, sometimes with a small forward jet to attack an obstruction directly. Most of the energy is deliberately aimed the wrong way.

Thrust is what results. It has to exceed the friction of the hose against the pipe wall and any bends, which is why long runs and multiple bends need more thrust than a short straight lateral.

The rearward jets do the cleaning as the hose is withdrawn, scouring the pipe wall and flushing debris back towards the chamber. The cleaning happens on the way out, not on the way in.

This is why a jetter cannot be replaced by a lance, and why a nozzle with the wrong jet angles will either not travel or not clean.

Flow determines thrust and how much debris is carried away; pressure determines what the jets can cut. Pipe diameter and run length set both.

Small-diameter domestic pipework needs relatively little flow, and too much simply backs water up because the pipe cannot carry it away. Portable machines suit this work.

Larger commercial pipes and sewers need substantially more flow, both to generate the thrust to travel a long run and to flush a meaningful volume of debris back down the pipe.

Pressure matters for what the jets are attacking. Soft blockages and grease respond at modest pressure; hard scale and compacted deposits need more, delivered through a rotating head.

Because the trade-off is genuine, specify by the pipe sizes and lengths actually on the books rather than buying the biggest machine - an oversized jetter on small pipework is unusable.

A general flushing nozzle to travel and rinse, a penetrating nozzle for a solid obstruction, a rotating nozzle for grease and scale, and a cutter for roots.

General or flushing nozzles have rearward jets only, or a very small forward jet. They travel well, flush effectively and are what most work is done with.

Penetrating nozzles put more energy forward to bore through a blockage, then a general nozzle follows to clean the pipe properly. Boring a hole is not cleaning the pipe.

Rotating nozzles spin a jet around the pipe wall and are what removes grease, scale and encrustation. They cut faster and can damage weak pipework, so they need judgement.

Root cutting uses chain flails or specialised cutting heads, and roots usually return unless the defect that let them in is repaired - which is a camera survey question rather than a jetting one.

Yes for domestic and light commercial drains with a proper jetting hose kit, and no for anything larger.

A jetting kit is a long, flexible, small-bore high-pressure hose with a jetting nozzle on the end, fitted to a standard machine. On short runs of small pipe it works well and is far cheaper than a dedicated jetter.

The limits appear quickly. Flow is usually too low to generate thrust for long runs, hose length is limited, and there is no reel, so handling a soiled hose is unpleasant and slow.

There is a safety dimension: a jetting hose that comes back out of the pipe with the trigger open is dangerous, which is why proper kits use a nozzle that will not reverse out and operators are trained not to withdraw under pressure past the chamber.

For a business doing drainage work regularly, a purpose-built jetter pays for itself in handling alone.

Confined space rules for chambers, contamination control for foul water, and never letting the nozzle come out of the pipe under pressure.

Entering a chamber is confined space work in most jurisdictions, with its own permit, gas testing, rescue and training requirements. Most jetting is done without entry precisely to avoid this.

Foul water carries biological hazard. Waterproof gloves and full face protection, washing facilities, covering cuts and awareness of waterborne infections are standard. The spray-back from a jetting nozzle is exactly the exposure route.

A pressurised nozzle emerging from the pipe will whip and can injure severely. Operators are trained to shut off before the nozzle reaches the chamber, and hoses are marked so the operator knows where the nozzle is.

Traffic management applies whenever chambers in a road or forecourt are opened, and an open chamber is never left unattended.

To find out what is actually wrong before jetting, and to prove the pipe is clean and structurally sound afterwards.

A blockage is a symptom. The cause may be grease, roots, a displaced joint, a collapse, a back-fall or something that should never have entered the drain. Jetting clears the symptom; only a survey identifies the cause.

Surveying before jetting risks a camera in a pipe full of debris; the usual sequence is to jet enough to restore flow, then survey properly, then jet again to a specification if required.

Post-work footage is what a client or insurer accepts as evidence. For repeat blockages, it is also what shifts the argument from cleaning to repair.

Coded survey reporting standards exist in most regions for describing defects consistently - if the work is for an asset owner, their required reporting standard should be established before the survey.

Back to the chamber, where it should be recovered rather than flushed downstream - and it is usually a controlled waste.

Jetting drives debris, silt, grease and roots back to the manhole. Allowing it to continue downstream simply relocates the blockage, often into an asset belonging to somebody else.

The proper method is interception and removal at the chamber, using a vacuum unit or manual recovery for smaller jobs. Combination jet-vac units do both in one machine, which is why they dominate commercial and municipal work.

Recovered material - particularly grease and interceptor waste - is generally a controlled waste requiring a licensed carrier and documented disposal.

Fresh water use is also worth planning. High-flow jetting consumes a great deal, and some units recycle the water they recover, filtering it for reuse.