Hose Pressure Loss Calculator
Estimate hose friction loss, fitting loss, elevation pressure, velocity, Reynolds number, and total pressure drop from flow, inside diameter, length, roughness, viscosity, density, and temperature.
Choose a common liquid hose case. Each preset fills flow, ID, length, roughness, fittings, fluid viscosity, density, elevation, and temperature.
| Hose or tube surface | Typical roughness | Use when | Pressure loss effect |
|---|---|---|---|
| Smooth rubber or PVC | 0.00005 to 0.00008 in | Clean water, washdown, food hose | Usually controlled more by ID and flow than roughness |
| Hydraulic hose bore | 0.00006 to 0.00012 in | Oil return, pressure, and suction hoses | Viscosity often controls Reynolds number |
| Aged or scaled hose | 0.00015 to 0.00040 in | Older water hose, mineral buildup, dirty service | Can raise turbulent friction noticeably |
| Corrugated suction hose | 0.001 to 0.006 in | Flexible suction, vacuum, slurry, temporary intake | Use conservative roughness and verify with field pressure |
| Fitting or device | Typical K | Count as | Note |
|---|---|---|---|
| Straight quick coupler | 0.15 to 0.40 | One fitting | High-flow couplers are usually lower than small restrictive couplers |
| 90 degree elbow or bend | 0.6 to 1.5 | One bend | Tight molded bends and kinked hose runs act like high K fittings |
| Ball valve, open | 0.05 to 0.25 | Valve K | Partly closed valves can be many times higher |
| Nozzle, strainer, check valve | 1.5 to 8.0 | Extra K | Use manufacturer data when available because device geometry dominates |
| Liquid service | Velocity target | Watch point | Practical check |
|---|---|---|---|
| General water hose | 3 to 8 ft/s | Noise and pump loss | Higher speed may be acceptable for short intermittent runs |
| Fire or washdown | 6 to 15 ft/s | Nozzle pressure | Confirm required residual pressure at the tool or nozzle |
| Hydraulic suction | 2 to 4 ft/s | Pump inlet vacuum | Use very low loss to avoid cavitation and aeration |
| Hydraulic return | 5 to 10 ft/s | Heat and backpressure | Oversize if oil is cold or line has many fittings |
| Fluid | Density | Viscosity near 70 F | Temperature effect |
|---|---|---|---|
| Water | 62.3 lb/ft³ | 1.0 cP | Viscosity falls quickly as water warms |
| 30 percent glycol | 64.5 lb/ft³ | 2.7 cP | Cold glycol can multiply pressure loss |
| ISO 32 oil | 53.5 lb/ft³ | 32 cP | Cold oil may become the controlling design case |
| Diesel fuel | 52.0 lb/ft³ | 3.0 cP | Moderate temperature sensitivity |
Pressure loss within a hose can be caused by various reason. Friction, the fittings within the hose system, and also the change in the elevations of the system cause the pressure loss within a hose. Each of these factors will contribute to the total pressure loss within the hose system.
If the fluid within the hose move too slowly through the nozzle, or if the pump is struggling to push the fluid through the hose system, pressure loss is occurring. To understand the total amount of pressure loss within the hose system, it is important to account for each of these factors: friction, fittings, and the change in elevation within the system. The amount of pressure loss that occurs within a hose is related to the velocity of the fluid within the hose and the inside diameter of the hose.
Why Hoses Lose Pressure
If the inside diameter of the hose is small, the velocity of the fluid that pass through the hose has to increase in order to maintain the same flow rate within the system. Since velocity and friction is directly related, an increase in the velocity of the fluid will lead to an increase in the friction between the fluid and the inside wall of the hose. Thus, a small diameter hose will experience more friction and pressure loss than a hose with a large inside diameter.
The roughness of the inside wall of the hose can also affect the friction between the fluid and the inside wall of the hose. A rough wall will experience more friction than a smooth inside wall, thus leading to a greater loss of pressure within the hose. The fittings and devices that is contained within the hose system will also contribute to the pressure loss within that system.
Each of the fittings, such as elbows, valves, and quick couplers, will restrict the fluid within the system and lead to a loss of pressure. Each of these component has a resistance value, known as a K factor. The K factor can be used to calculate the amount of pressure loss that the fitting will cause.
Many people underestimate the effect that these fittings has on the system; they often do not account for every fitting within the system. If you dont count every fitting within the hose system, the total pressure loss will be calculated incorrectly. Therefore, in the calculation of total system pressure loss, every fitting within the system should be accounted for.
Another factor that contributes to pressure loss is the change in the elevation within the system. If the outlet of the hose system is higher than the inlet of the system, the pump will have to work harder to move the fluid against the force of gravity. This change in elevation within the system creates a requirement for more pressure within the system.
However, if the outlet of the hose system is lower than the inlet of the system, the system will gain in pressure due to elevation. The static pressure that is created as a result of these elevation changes must be accounted for when calculating the total pressure loss within the hose system. One more factor to consider is the viscosity of the fluid that is moving through the hose.
Viscosity is a factor that indicates how much the fluid resist flowing. Cold fluids will have high viscosity, which will contribute to the loss of pressure within the hose system. Warm fluids will have low viscosity, which will contribute to the decrease in the loss of pressure within the hose system.
Therefore, one must consider the viscosity of the fluid when calculating pressure loss; viscosity and temperature are directly related. The viscosity of the fluid must be calculated according to the coldest temperature at which the fluid will exist within the system. Velocity is one more constraint that must be considered when fluid is to move through a hose system.
If the velocity of the fluid is too low, the nozzle may not perform as it should within the system. Too high of a velocity, however, can cause erosion of the nozzle, the system emits loud noise, and water hammer can occur within the system. The velocity and the Reynolds number for the system can be used to calculate the safe range of velocities for the fluid within the system.
Many people make mistakes when calculating pressure loss. For instance, many people use the nominal size of the hose to calculate pressure loss rather than the actual inside diameter of the hose system. Using the nominal size will understate the inside diameter of the hose system; therefore, the velocity and friction calculations will not accurately reflect the true pressure loss within the system.
Additionally, people often do not account for pressure loss at the nozzle or within the hose reel. To account for these mistakes, it is important for an individual to measure the inside diameter of the hose system. Furthermore, every component attached to the hose should be accounted for in the calculation of total system pressure loss.
Finally, it is important for an individual to compare the calculated pressure loss within the system to the capability of the pump that is to be utilized within the system. If the pressure loss within the hose system is too high for the pump to provide, that system will not function properly. In addition to the pressure loss within the system, one should check the pressure ratings of the systems couplers, as well as the burst ratings of the hoses.
Thus, in addition to calculating the total pressure loss within the system, an individual must also account for the pressure capabilities of each component of the system to ensure the safety and functionality of that system.
