Enter a jetter's pressure (500 to 5,000 psi), flow (0.5 to 80 gpm) and the line size you want to clean. The calculator returns hydraulic horsepower (psi × gpm ÷ 1,714, to one decimal place), the rig class the flow puts the machine in, the rig usually paired with that line size, and flags for low flow, a pressure-washer rig on a large line, or high pressure on a small line.
- Hydraulic horsepower combines pressure and flow into one number: psi multiplied by gpm, divided by 1,714.
- Rig class comes from flow alone: under 3 gpm, 3 to 8, over 8 up to 20, and over 20 gpm.
- Line size maps to the rig the pressure-vs-flow pairing table suggests, so the two can be compared side by side.
- Three flags catch common mismatches, and the injection-injury safety note always appears.
- The result describes a machine's rating, not what reaches the nozzle, and it does not predict cleaning results.
Jetter Power Calculator
01 /What does the Jetter Power Calculator do?
The Jetter Power Calculator turns the two numbers on a jetter's specification plate, pressure and flow, into a quick reading of what class of machine it is, how much water energy it delivers, and whether it is the kind of rig usually matched to the line you want cleaned. It uses the same formula, classes and pairing table as the pressure vs flow guide, so every result can be read against that explanation.
It is useful in three situations: comparing two contractors who describe different rigs, checking a rental machine's numbers before you take it home, and understanding why a pressure washer kit that works on a bathroom branch struggles in a building sewer. It does not see your pipe, choose a nozzle, or estimate a price.
02 /What do you enter?
You enter three things: the machine's rated pressure, its rated flow, and the size of the line to be cleaned.
| Input | Range or options | Where to find it |
|---|---|---|
| Pressure | 500 to 5,000 psi | The machine's rated pressure on its label, specification sheet or rental tag |
| Flow | 0.5 to 80 gpm (US gallons per minute) | The rated flow from the same source; contractors can tell you their rig's figure |
| Line size | 1.5–2 in, 3 in, 4 in, 6 in, or 8 in and larger | The pipe being cleaned: branches are usually 1.5–2 inches, most house building sewers 4 inches |
If you type a number outside those ranges, the calculator works with the nearest limit instead, so a 6,000 psi entry is treated as 5,000 psi. Use the rated figures as a pair from the same source. If a machine is rated in metric units, convert first: 1 bar is about 14.5 psi, and 1 litre per minute is about 0.26 US gallons per minute, since one US gallon is about 3.785 litres. A pump rated at 200 bar and 30 L/min, for example, works out to roughly 2,900 psi and 7.9 gpm.
03 /How is hydraulic horsepower calculated?
Hydraulic horsepower is calculated as pressure in psi multiplied by flow in US gallons per minute, divided by 1,714, and the calculator shows the result to one decimal place. The constant 1,714 converts psi and gpm into horsepower, and it only works with those units, which is why metric ratings need converting first. For readers who prefer metric, the equivalent is bar multiplied by litres per minute, divided by 600, which gives kilowatts; one horsepower is about 0.746 kilowatts.
| Example rig | Pressure | Flow | Hydraulic hp |
|---|---|---|---|
| Consumer pressure washer | 3,000 psi | 2 gpm | 3.5 |
| Small cart jetter | 3,000 psi | 5 gpm | 8.8 |
| Trailer jetter A | 4,000 psi | 12 gpm | 28 |
| Trailer jetter B | 3,000 psi | 18 gpm | 31.5 |
Your result appears next to these four examples so you can see where a machine sits. Trailer B, at lower pressure, carries more energy than trailer A because of its flow. That is the central point of hydraulic horsepower: a pressure figure on its own can hide a small machine.
04 /How does the calculator assign a rig class?
The rig class comes from flow alone, because flow separates a pressure washer from a sewer jetter far more reliably than pressure does. Two machines rated at 3,000 psi can be a consumer washer and a trailer jetter; their gpm tells them apart.
| Flow | Rig class shown | What that class usually means |
|---|---|---|
| Under 3 gpm | Pressure-washer kit class | A consumer pressure washer driving a jetter kit, or a very small electric unit |
| 3 gpm up to and including 8 gpm | Small electric or cart | Plug-in drain jetters and small gas carts for branch lines |
| Over 8, up to and including 20 gpm | Trailer | Towed jetters with a water tank; the usual residential sewer rig |
| Over 20 gpm | Truck or combination unit | Truck-mounted jetters and jet-vac trucks for large lines and mains |
Classes describe typical equipment, not brands or models. A machine rated close to a class boundary, at 7.5 or 8.5 gpm for example, is effectively between classes, and the neighbouring description may fit it just as well. The equipment in each class is described in sewer jetting machines.
05 /How does line size affect the result?
For the line size you choose, the calculator shows the rig that the pairing table in pressure vs flow suggests as a starting point. Comparing it with the class your flow produced tells you whether the machine is in the usual range for that pipe. That line carries a 'Use with care' badge whenever one of the flags below is raised, and a 'Recommended' badge otherwise, which simply means none of the three mismatch checks was triggered.
| Line size | Typical location | Rig that usually suits |
|---|---|---|
| 1.5–2 in | Kitchen, bathroom and laundry branches | Small electric or cart jetter, lower flow |
| 3 in | Stacks and some building drains | Cart or trailer jetter |
| 4 in | Most house building sewers and laterals | Trailer jetter, mid-teens gpm |
| 6 in | Larger laterals and small commercial lines | Larger trailer jetter |
| 8 in and larger | Commercial and municipal lines | Truck or combination unit |
A match between the two is reassuring but not proof that the job will go well; nozzle choice, hose, pipe condition and operator skill still decide the outcome. A mismatch is a prompt for a question, not a verdict.
06 /What do the warning flags mean?
Beyond the side-by-side comparison, the calculator raises specific flags for three common mismatches, and it always shows a safety note.
| Flag | Trigger | What it means |
|---|---|---|
| Low flow | A 4 in or larger line with flow under 5 gpm | Warns that the flow may open a channel but will not carry debris out. Loosened material is likely to settle downstream, and the nozzle has little pull in a large pipe |
| Pressure-washer rig on a large line | A pressure-washer-class flow (under 3 gpm) on a 4 in or larger line | A warning that consumer-class equipment is mismatched to a building sewer or larger pipe |
| High pressure on a small line | Over 4,000 psi on a 1.5–2 in line | A caution for small plastic lines and fittings, where extra pressure adds risk without adding much cleaning |
| Injection-injury safety note | Always shown | A reminder that a jetter stream can inject water through skin, that no pressure is safe to touch, and that nozzle, hose and operator skill matter as much as the number |
A pressure-washer-class machine on a 4-inch line triggers both the low-flow flag and the pressure-washer warning, because anything under 3 gpm is also under 5 gpm. Together they describe the most common DIY disappointment: a nozzle that stalls a few metres in, and a line that clogs again as soon as the loosened grease settles. The reasons are explained in garden hose and pressure washer jetter nozzles, and plastic-line cautions in is hydro jetting safe for PVC and ABS.
07 /What are the limits of the calculator?
- Rated, not delivered. It uses the pump's rated pressure and flow. Hose friction means the nozzle sees less pressure than the pump makes, especially on long, thin hose, and worn pumps or nozzles deliver less than their rating.
- No nozzle, hose or distance. It does not know which nozzle will be used, the hose size or length, or how far the blockage is from the access point.
- No pipe condition. It cannot tell whether the pipe is sound, fragile, sagging or broken; that takes a camera. The jet-or-auger decision tool handles the question of method.
- No blockage type. Grease, roots, sand and ice respond differently to the same machine.
- No water temperature. Hot-water capability matters for grease and thawing and is not an input.
- Not a buying recommendation or a quote. The classes are general. For service pricing, see hydro jetting cost.
- US gallons only. Flow is in US gallons per minute, the unit North American jetters are rated in; an imperial gallon is about 20 percent larger.
SewerJetting.ca belongs to HAUSE Sewer, an independent information and quote-request network rather than a drain contractor. The calculator is a reading aid for equipment numbers; the operator on site makes the equipment decisions.
08 /How should you use the result?
Use the result to ask better questions. If a contractor proposes jetting a 4-inch lateral, ask for the rig's psi and gpm, run them through the calculator, and see whether the class matches the line. If a rental counter offers a unit, check whether its flow suits your line before paying for the day. If two quotes name different machines, hydraulic horsepower and flow compare them more fairly than a pressure figure alone.
- Get the numbers
Ask for the rated psi and gpm from the same specification sheet, and note the hose size and nozzle plan if they are offered.
- Enter them with the line size
Choose the line you actually need cleaned, not the biggest pipe in the house.
- Read class, horsepower and flags together
No single figure is the answer; a flag matters as much as the horsepower.
- Ask about anything flagged
A good operator can explain why a particular rig and nozzle suit your line, or what they will do differently.
- Decide the method separately
Whether to jet at all is a different question, answered by the blockage and the pipe's condition.
When you are ready to compare contractors, the quote request form lets you describe the line so they can tell you which rig they plan to bring.
FAQQuestions people ask
How do you calculate jetter horsepower?
Multiply pressure in psi by flow in US gpm and divide by 1,714. A 4,000 psi, 12 gpm jetter delivers about 28 hydraulic horsepower.
Is hydraulic horsepower the same as engine horsepower?
No. Engine horsepower drives the pump; hydraulic horsepower is the water energy the pump delivers, which is lower because of pump and drive losses.
What gpm do I need for a 4-inch sewer?
The pairing the calculator uses suggests a trailer jetter in the mid-teens of gpm for 4-inch lines. Flow under 5 gpm on a 4-inch or larger line triggers the low-flow flag.
Why does the calculator flag high pressure on small lines?
Over 4,000 psi on a 1.5–2 inch line adds risk to small plastic pipe and fittings without adding much cleaning, so it shows a caution.
Can I enter metric ratings?
Convert first: 1 bar is about 14.5 psi and 1 L/min is about 0.26 US gpm. The calculator works in psi and US gallons per minute.
Does higher horsepower mean better cleaning?
Not by itself. It compares machines more fairly than psi alone, but the nozzle, hose, pipe condition and operator skill decide the result.
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