Most sewer districts and contractors think carefully about their jetters, which makes sense — after all, a new truck is an investment of $300,000 or more. But operators should think just as carefully about the nozzles they use, because a bad nozzle deletes most of the value of an expensive jetter. If a cheap nozzle scatters and diffuses a jetter’s high-pressure flow, weakening it, then you might as well be working with a garden hose. On the other hand, the right nozzle can raise the performance of any system by making maximum use of the available pressure and flow.
As AquaTeq’s Bo Larson says, “Operators need to be educated not only on the truck, but on how nozzles really work at the other end of the hose. A $69 nozzle defeats the whole purpose of the system.”
In other words, the nozzle isn’t the end of your sewer jetting system — it’s the beginning.
Cleaning a sewer line is really no big deal — if you have all day and don’t really care how much water, wear and tear, energy and man-hours it takes. But cleaning sewers efficiently takes skill and knowledge. Simply put, if you can reduce the number of pulls it takes to clean a length of sewer, you’ll save money and time and you won’t have to replace or repair equipment nearly as often.
That’s why the relationship between water flow and pressure is so important. It’s also commonly misunderstood. To be successful, operators need to know the power of their jetting unit and understand what that means at the nozzle end of the hose. Here are a few quick thoughts on nozzles and pressure.
Moving debris through a sewer is easy to understand intuitively. Just think about taking a handful of sand, gravel and stones into a creek. If the creek is moving slowly, then the gravel and stones will sink right to the bottom and the sand may not move downstream very far either. But if the creek is moving very quickly, all of this material will be moved downstream. And that illustrates what we want at the nozzle end of the jetting systems: fast, smoothly flowing water.
Intuitively, you would think that more pressure from the jetter always equals more efficiency at the nozzle end. But this is definitely not the case — sometimes more pressure means less effective cleaning and vice versa.
Here’s why: Depending on the nozzle, lower water pressures will create a ‘jet stream’ as the water leaves the nozzle. That’s because the water flow emerges in a ‘laminar flow,’ meaning that the water particles all move in parallel. It’s a little like pouring water from a bottle. When you start to pour, the water comes out smoothly, but as you pour faster the water starts to ‘glug,’ meaning that the flow has become turbulent.
Similarly, the best pressure for your system is just high enough to produce a smooth, efficient flow through your nozzle, but not so high that the flow breaks down and becomes turbulent. More pressure does not always equal better cleaning.
With the right pressure, the flow from the nozzle gathers into an efficient jet stream. If the pressure is too high, the flow will break down into water drops, and eventually a misty spray that does not clean lines efficiently.
NozzTeq Inc. ran numerous tests with 27 different nozzles and learned that when it comes to moving debris out of lines, water pressure at the nozzle end should not exceed 900 psi.
The basic components of a jetting system are the pump, hose and nozzle. Figuring out your available nozzle-end pressure is a function of pump psi, pump gpm and hose length. Once you know that, you can select nozzles that make the best use of your available nozzle end pressure. Consider the following table (see table on pg. 52 for reference):
Nozzle end pressure decreases as hose length increases. To perform the calculation, find the appropriate factor in the table and multiply it by the number of 33-ft segments in the hose.
For example, suppose you have a pump that moves 80 gpm at 2,000 psi and are using 1,000 ft of 1-in. hose. First, divide hose length by 33 to get the number of 33-ft segments; in this case that’s about 30.3 segments. Then use the table to find the appropriate factor for your pump and hose diameter; in our example, that factor is 49. Then, multiply the factor by the number of segments and subtract the result from the pump end psi. So, for our example, you multiply 49 psi times 30.3, to get 1,484.7 psi, and subtract that from 2,000 psi to get a nozzle-end pressure of 515.3 psi
Clearly, available psi can vary quite a bit depending on hose choices, and it may be worth verifying nozzle-end psi with an inexpensive test.
Nozzles: What to Look for
Remember, all the jetting pressure in the world is wasted if a poorly designed nozzle creates a turbulent flow and diffuses the jet stream. Good nozzles perform better and last longer, and it doesn’t make sense to choose a nozzle based solely on price.
It really doesn’t matter what the outside of a nozzle looks like — it’s the inside design that makes a difference. Good inner design minimizes turbulence and creates a powerful, effective jet stream that cleans efficiently and minimizes wear on your jetter. Properly engineered nozzles made of durable materials, like stainless steel, can last 10 to 20 years. It’s okay to put money into jets or orifices, but don’t forget that the design and manufacturing quality of the actual nozzle is also incredibly important.
Bottom line? Always look for good materials and good design in nozzles.
Jetting Your Nozzle
We recommend choosing the best nozzle for a particular job. For example, if you’re cleaning a 36-in. line, you probably want a bottom cleaner that directs flow to the bottom of the line. But there are other factors to consider, and it’s always a good idea to talk to your dealers, see what’s available and maybe arrange for tests in your lines.
One consideration that always applies is the number of jets in a nozzle — fewer are better. Fewer is better in pipe cleaning because an increase in total jet size expands the total area cleaned and applies less pressure to the pipe surface. Think about cleaning a pile of sand with a fire hose or a garden hose: Which would clean quicker, if all factors were equal except the size of the hose?
Know your system’s pressure at the nozzle end and check it before choosing a nozzle. Then, choose a nozzle that’s right for your system, one that’s designed to preserve a smooth, efficient jet stream and made of durable materials. When comparing nozzles, look for a few jets as possible and bigger diameter as possible, with the jets at a low angle. Low angles increase the speed of the water and increase power.
Finally, remember that a jetting system is never better than its nozzle, and that’s why the nozzle is the beginning of the system, not the end.
Scott A. Paquet is president and CEO of NozzTeq Inc., Clearwater, Fla.