Sewer line cleaning is one of the most routine maintenance tasks for wastewater utilities, but the way it is carried out can have a major effect on water use, equipment wear and service disruption.
For UK water and wastewater operators, cleaning sewer lines means removing grease, sediment, roots, sludge and debris before they restrict flow, cause backups or contribute to wider network problems.
The equipment matters. Jetting vehicles and high-efficiency nozzles can deliver powerful cleaning performance. But effective sewer cleaning still depends on how well the operator matches the equipment to the conditions inside the pipe.
Why nozzle performance depends on the operator
A high-performance sewer nozzle is often compared to a race car. It is engineered to deliver strong results, but buying one does not automatically provide the knowledge needed to operate it effectively.
The same principle applies to sewer jetting. Even an advanced high-efficiency nozzle can underperform if the operator does not understand how nozzle selection, water flow, jetting vehicle engine speed, pressure and hose travel speed interact.
A Tier 3 sewer cleaning nozzle is designed to control the way water moves through and exits the tool, converting more of the jetting vehicle’s available energy into usable cleaning and pulling force. But the nozzle is only one part of the cleaning system.
The operator still needs to find the right operating range for the line being cleaned.
“The goal is to help operators understand what the pipe is telling them, so they can lower the RPMs, control the flow and clean the line in one pass instead of forcing the jetting vehicle to do all the work,” said Dan Story, Application Specialist at KEG Technologies.
Finding the right operating range
Many operators respond to difficult cleaning conditions by increasing pressure and flow. The assumption is that running the jetting vehicle harder will produce a better result.
In practice, excessive pressure can increase friction loss as water moves through the hose. It can also use more water than necessary, place additional strain on the vehicle and increase the risk of forcing air or water into residential sewer connections.
During a recent field training session with a municipal wastewater utility, Story demonstrated how crews could reduce engine RPMs and operating pressure while maintaining effective cleaning force.
In one exercise on a line known to be difficult to clean, the crew limited operating pressure to around 83 bar, or 1,200 psi, and controlled the nozzle speed carefully.
Story said operators were able to control flow at approximately 132 to 151 litres per minute and complete the work in one pass.
“A 200-, 250- or 300-millimetre sewer pipe never needs more than 151 litres a minute to clean it,” Story said. “You have to learn to get that flow down to match the size of pipe you are cleaning.”
The correct settings will vary from line to line. A relatively clean pipe allows faster nozzle travel. A line containing sediment, grease or other material requires slower movement so water can break up and carry debris toward the downstream manhole.
Reading the water returning from the pipe
Because operators cannot directly see what is happening underground, the water and debris returning at the downstream manhole provide important information.
“If you pay attention to what comes out of that invert, it is telling you how to clean the pipe,” Story said.
The volume of debris, sediment colour and changes in returning flow can all indicate conditions farther upstream.
If little material is returning, the operator may be able to increase travel speed. If heavy debris begins to appear, it is usually a signal to slow the nozzle and give the water enough time to move material out of the line.
A sudden colour change can also matter. If returning water changes from light grey to black, it may indicate that the nozzle has entered a belly, or low section of pipe, where stagnant water and debris have accumulated.
In that situation, continuing to force large volumes of water into the pipe can fill the low area and increase pressure toward nearby service connections. A more controlled approach gives the system time to clear before continuing upstream.
Clean going in, rinse coming back
Travel direction is another important part of sewer line cleaning technique.
A common approach is to send the nozzle quickly to the upstream manhole and try to remove accumulated debris while pulling the hose back. This can leave the operator trying to move a large amount of material at once.
“If you shoot the nozzle all the way upstream and then try to clean on the way back, it is like digging a hole from the bottom up,” Story said.
Instead, Story teaches operators to clean while advancing upstream. Moving at a controlled pace allows the nozzle to loosen material gradually, while existing flow carries debris toward the downstream manhole.
“You clean going in. Let it stir the material up and let the flow carry it out. As you come back, you should be giving it more of a final rinse,” Story said.
After the main cleaning work has been completed on the way upstream, operators can reduce pressure and rinse the pipe as the nozzle returns.
When flow, pressure and speed are matched to the pipe, the line can often be cleaned without sending the nozzle through a second or third time. This reduces water use and helps keep the jetting vehicle operating for longer before the crew needs to refill.
Reducing service disruption
Proper technique can also reduce the risk of blown toilets and other customer-facing problems.
If a nozzle moves too quickly through a line, debris can accumulate into a large obstruction that traps and compresses air. As that pressure passes a residential service connection, air and water can be forced through the lateral and into the home.
“Ninety-five percent of blown toilets are operator-related,” Story said. “Most of the time it’s not the homeowner’s plumbing. It’s how the line is being cleaned.”
Cleaning gradually on the way into the line, using only the water required for the pipe diameter and responding to changing conditions can help operators maintain control of the process.
Taking the guesswork out of field adjustments
To help operators identify efficient settings more quickly, Story uses a pressure-and-flow spreadsheet that links nozzle jetting, operating pressure and expected water flow.
The chart allows crews to select a nozzle configuration and estimate how much water it will deliver at different pressures. Operators can then compare that information with pipe diameter and field conditions rather than assuming higher RPMs or pressure will improve cleaning.
The approach gives crews a practical baseline, but field observation remains essential. The operator still has to watch what is returning from the line and adjust accordingly.
After the field training, wastewater collection supervisor Leon Marquez said the techniques helped his crew save water, work more efficiently and view their process differently.
“The techniques and information he instructed helped my crew tremendously to save water, work more efficient, and see our process in a better way,” Marquez said.
The training illustrates why nozzles, jetting vehicles and operator skills need to work together. When crews learn to find the operating sweet spot, they can reduce repeat passes, avoid unnecessary equipment strain and lower the risk of service disruption.
More information is available from KEG Technologies.
FAQs
What is the “sweet spot” in sewer line cleaning?
The sweet spot is the operating balance between nozzle selection, water flow, pressure and nozzle travel speed that matches the pipe diameter, hose length and amount of material in the line.
Why is higher pressure not always better for sewer cleaning?
Higher pressure can increase friction loss in the hose, waste water, strain the jetting vehicle and increase the risk of forcing air or water into service connections.
How much flow is needed for typical sanitary sewer cleaning?
According to KEG Technologies trainer Dan Story, 200-, 250- and 300-millimetre sewer pipes generally do not need more than around 151 litres per minute when the nozzle and technique are matched correctly.
Why should operators watch the water returning from the downstream manhole?
The colour, flow and debris in the returning water can indicate what is happening inside the pipe, helping operators decide whether to speed up, slow down or adjust settings.
How can sewer cleaning technique reduce blown toilets?
Cleaning gradually while advancing upstream can reduce the risk of debris and compressed air building into a surge that reaches residential service laterals.
