Cleaner Classroom: Jetting 201

Figuring out which water jetter best suits your needs requires some calculated thinking and an eye to the future.
Cleaner Classroom: Jetting 201
In general terms, larger-diameter pipes require higher flow, while smaller pipes require higher pressure.

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Editor’s note: Cleaner Classroom is an online series focused on the fundamental functions of cleaning professionals and the basic tools used to clean, inspect and rehabilitate water, sewer and drainlines.

Now that you’re familiar with the kinds of water jetters available and understand how they work, it’s time to hone in on a critical question: Which of these jetters best suits your needs?

The answer to that question depends on several variables. But first, it’s important to understand the basic principles of waterjetting — pressure and flow. Measured in psi, pressure refers to the force with which the water is propelled through a hose via a high-pressure pump. Water is forced through small holes in a nozzle/cutting head that does the cleaning. Flow, measured in gpm, is a function of hosepower and pressure and refers to the volume of water going through the hose, which carries away dislodged debris.

In general terms, larger-diameter pipes require higher flow, while smaller pipes require higher pressure.

“If you mainly clean bigger lines, you need more flow to flush out all the debris,” says Tim Gage, the Ohio territory manager for Spartan Tool, which offers a full line of jetters aimed at various applications. “For smaller lines, you usually want more pressure, especially if you’re cleaning heavy greases or clearing tree roots.”

A smaller cart-mounted jetter with a 1.5 hp electric motor generates about 1,500 psi at 1 1/2 to 2 1/4 gpm and is suitable for cleaning pipes up to 4 inches in diameter. In other words, these smaller units are best suited for cleaning interior residential lines. If you mostly tackle lines up to 6 inches in diameter, a 13 hp unit (with a gas-powered engine) that generates 3,000 psi at 4 gpm should do the trick. And to clean lines ranging from 3 to 12 inches in diameter, you’ll need an even larger trailer-mounted unit with a gas engine that ranges from 19 to 40 hp and produces anywhere from 2,000 to 4,000 psi at about 12 gpm. For even larger pipes, the horsepower and gpm metrics increase exponentially while the pressure specs remain in the 3,000 to 4,000 psi range.

Brian Gilbert, the national sales manager for Harben, which builds a wide range of water jetters, says contractors need to think carefully about the future. “You might be interested in just residential work right now, cleaning only 3- to 6-inch-diameter lines, but where do you see your company in five years?” he asks. “Do you want to bid on municipal or commercial jobs with 10- to 12-inch drainlines or larger industrial pipes? And what about storm drains, which are up to 36 inches in diameter? You can’t do that with a machine that generates 4,000 psi at 18 gpm. Bigger pipes require more flow, so 4,000 psi at 25 gpm would work better for some of those applications.”

The bottom line: Don’t buy an undersized machine, Gilbert advises. “You need to try and look into the future, which isn’t easy to do.”

Modifications and considerations
But if contractors invest in a much larger unit, don’t they give up the option of cleaning smaller lines? Not necessarily, Gilbert says, thanks to a technological advancement called a flow diverter. A flow diverter can be set to divert a specified amount of water back to the water tank, which reduces the flow output. This enables a contractor with, say, a 4,000 psi/25 gpm water jetter to drop the flow down far enough to switch to a 1/4-inch hose and clean smaller-diameter pipes. “It essentially gives you more versatility,” Gilbert says.

Spartan jetters basically accomplish the same thing via an unloader valve, also known as a pressure-relief valve. It can reduce the flow on a large jetter from 18 gpm down to 3 gpm, for instance — low enough to switch from a 1/2-inch-diameter hose to a 1/4-inch hose that can be used to clean a kitchen sink drainline, for example.

“The unloader regulates what you need and sends any extra water into a holding tank,” Gage says. “Then you can use an auxiliary reel to step the larger hose down to a smaller hose with a smaller nozzle.”

Other factors require some thought, too. What kind of material or debris and what size pipes will you be dealing with the most? If it’s 3- to 4-inch lines filled with rock and sludge, a smaller cart-mounted, electric-powered jetter won’t do the trick. Do you often have to cut through tree roots? If so, you’ll need a powerful, high-pressure unit. And how long of a hose run will your typical jobs require? Since water pressure tends to drop as the hose run increases, a more powerful unit is needed to compensate for longer runs, Gage notes.

“You also need to keep in mind that our jetters’ pressure ratings are measured at the end of the hose,” he says. “If you’re looking at a machine with 4 gpm at 3,000 psi — which usually comes with 200 feet of hose — that 3,000 psi is measured at the end of the hose. If you add more hose, you lose about 1 pound per foot, on average. A lot of jets are rated right at the pump, so guys looking at getting into jetting should ask where the water pressure is rated at, the pump or at the end of the hose.”

The kind of pipes commonly found in your area also could influence your decision. PVC pipe can withstand higher-pressure jetting. Old Orangeburg pipes? Don’t even think about it. “And if you run into a lot of galvanized pipes, especially in restaurants, they often develop ‘bellies’ where the pipe has been eaten away,” Gage says. “Sometimes a jetter will cut right through there.”

If you buy a bigger trailer-mounted jetter, you also have to consider your vehicle’s towing capability. “Some of our larger water tanks go up to 600 gallons, which comes out to 8 pounds per gallon for just the water alone, not including the tank,” Gage says. So you may need to factor the cost of a new truck into your decision. On the other hand, you can typically charge customers more money when using a larger jetter, plus they enable you to finish jobs faster. That, in turn, allows you to do more jobs per year and make more money, he says.

“On our website, we have a calculation chart that allows you to enter the (monthly) payments for a machine, plus estimate material and labor costs, and it calculates what the machine can earn for each job,” Gage says. “So if a guy is looking at a $20,000 machine but really wants a $40,000 machine, he can do the calculations and maybe he finds out it costs only $100 a month more for the larger machine.”

Gilbert also recommends considering more than just the jetter’s price. “First of all, you get what you pay for,” he says. “Price always is a factor, but at the same time, make sure you study and learn what everyone is producing. Look at warranties. Talk to others who have purchased and operate the same machine. Get references. Do your homework. Don’t buy a machine just because it’s $3,000 cheaper than another one.”

Contractors also need to consider the cost of ownership. For example, one jetter may cost less than another, but the lower-cost model might include a less-durable pump that will incur ongoing costs for periodic rebuilding or even replacement, Gilbert says. “There’s also a cost to the resulting downtime for repairs.”

Up next: Selecting the right nozzle for the job.


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