A 12-volt diaphragm pump is one of the most versatile pumps used for low-volume applications. They are often used on ATV and UTV sprayers, spot sprayers, small boom sprayers, mobile washing, automotive liquid transfer, and marine applications.
These pumps are especially useful for applications where 110-volt power is unavailable. While they work fantastic, they can cause problems if they are not set up and used correctly. With their widespread use, it is essential for individuals working in any of these industries to know how these pumps operate, how to install them, use them, and repair them.
In this article, we will aim to provide a complete guide to 12-volt diaphragm pumps. This information will be relevant to most 12-volt pump brands including Shurflo, Flojet, Delevan, Northstar, Remco, High-flo, Everflo, and more.
12-Volt Diaphragm Pump Applications
- Spot sprayers
- ATV sprayers
- Lawn and garden sprayers
- Soft wash
- Low-volume transfer of oils and chemicals
- RVs
- Boats
How 12-Volt Diaphragm Pumps Work
12-volt diaphragm pumps are positive displacement pumps that use a set of valves and a flexible diaphragm to move fluids. They are driven by an electric motor. The rotation of the motor spins a wobble plate. As the wobble plate spins it seals up and then opens the valves very rapidly. This creates suction and moves the liquid through the pump.
Demand vs Bypass
There are two main categories of 12-volt diaphragm pumps: demand and bypass. The difference between these two types of pumps is that a demand-style pump has a pressure switch on the pump head to shut off the motor at a certain pressure.
Demand Pump Operation: On the pump head, or the pump housing there is a small box or compartment that contains a micro switch, diaphragm, arm, and a spring. The switch in this box is connected to the motor that drives the pump. There is a small fluid path in the pump and switch housing that allows liquid from the inside of the pump chamber into the switch. This liquid pushes against the diaphragm in the pressure switch.
When the pressure inside the pump reaches a certain amount it pushes up against that diaphragm enough that it pushes a small arm against the electronic microswitch. When this happens the switch circuit opens and the power to the motor is cut. Stopping the pump from moving any more liquid.
When the pressure decreases, force on the diaphragm is also decreased. This lets the arm release from pushing the switch and closes the circuit. The motor then begins running again and the pump once again begins to operate.
Why would you want this? Well, many of you who have used a sprayer with a handgun already know the answer. This feature provides the operator with liquid “on demand” when they need it. The pressure switch on the pump works in conjunction with a trigger gun, spray wand, or any type of shut-off valve on the discharge side of the pump. Simply put, when the gun or valve is off, the pump shuts off, when the valve or spray gun is open, the pump runs.
This keeps the pump from overheating, saves battery, and prolongs the life of the pump. Adjusting the pressure that shuts this switch off, and installing a regulating valve to help the pump avoid cycling on and off are good practices. You can learn more in this article: “Why does my sprayer pump surge/cycle?”.
Demand pumps are often used on spot sprayers, soft wash setups, small boom sprayers, and sinks in RVs.
Bypass Pumps: A bypass-style pump does not have a pressure switch assembly on it. They are intended to be run continuously, only being turned on and off manually, when the user desires. They generally have a toggle switch installed to control power to the motor.
These pumps can be used for many of the same applications of a demand style but they are better suited for situations where consistent flow is needed. Such as low-volume transfer of light oils, anti-freeze, water, etc.
Parts of a 12-Volt Diaphragm Pump
- Diaphragm Assembly: wobble plate and flexible diaphragm
- Valve Assembly: a set of valves that allow liquid in when open, and force it out when closed. This movement pushes the liquid through the pump.
- Motor: Drives the pump
- Housing: These are the ports where the liquid enters and exits the pump.
- Pressure switch: Some diaphragm pumps have a pressure switch that turns the pump on and off depending on the pressure in the system.
Construction/Materials
12-volt diaphragm pumps can handle both water and non-water fluids, including chemicals, petroleum-based liquids, and pesticides. However, the materials that the pump and internal components are constructed with matter. Not all materials will be suitable for use with different liquids. For example, EPDM and motor oil typically don’t mix. In this case, you would want to have a pump with Nitrile internals.
There are different options available to best serve different industries and applications. The pump housings are generally polypropylene, with the valve assembly and diaphragm assemblies consisting of either Santoprene, Viton, Buna, or EPDM.
Here are the common pump materials and the common liquids they are generally compatible with:
| Material Name | Compatible Liquids |
| Viton | Bleach, fertilizers, acids, pesticides, oils, diesel |
| Buna | Hydraulic oil (petro), mineral spirits, methanol, gasoline |
| EPDM | Acetone, herbicides, pesticides, DEF, acetic acid, Anhydrous ammonia |
Capabilities of 12-Volt Diaphragm Pumps
There are many fantastic features of 12-volt diaphragm pumps that make them so versatile and appealing for different jobs. Although different models will vary in their materials, flow rate, and pressure, these basic characteristics are shared by all 12-volt diaphragm pumps regardless of model or manufacturer:
Self-Priming
One notable feature of these pumps is their self-priming capability. Self-priming pumps can draw liquid into them, even when the fluid level is below the pump inlet. This is done because the pump creates suction by evacuating the air in the suction line. This is a huge benefit that gives the user a lot of options when it comes to installing the pump.
Mobility
Another advantage of 12-volt pumps is their ability to be used in mobile applications. Because they run on a 12-volt battery, they can be connected to and run by the battery on almost any vehicle or piece of equipment. Even if you want to use a dedicated battery, they can be used on sprayers, mobile wash tucks/trailers, RVs, boats, trucks, or even in a cabin in the woods.
110 volts pumps may be capable of moving much higher volumes than 12-volt pumps but they must be installed where 110-volt power is available.
Flow Rate
A 12-volt pump is limited in the maximum flow it can produce because there is limited horsepower provided by a low-voltage motor. The maximum flow rates vary among different models but on average these pumps can achieve flow rates of around 1 to 5 gallons per minute (GPM).
Pressure
Pressure is also limited. The maximum pressure that a 12-volt diaphragm pump can produce is around 1000 psi. However, the flow rate of a 12-volt pump producing this much pressure is generally limited to less than 1 GPM flow. The amp draw on these pumps is also much higher, sometimes as much as 60 amps or more.
The most common pressure range is 40-60 for most 12-volt diaphragm pumps. But they are available in a wide range of options.
Thermal Overload Protection/Continuous Duty Motors
Electric motors can get hot when running. Most 12-volt pump motors are not “fan-cooled” or continuous duty. Instead, they have thermal protection built in. This means at a certain temperature the motor shuts off to prevent damage. The motors will typically be rated for a certain duration of constant use before they reach that temperature. Then they will need to cool down before starting again.
Some 12-volt motors are rated for continuous use, these are usually more expensive motors that are designed for low-volume liquid transfer and not used on sprayers or soft wash units.
Installation and Connection
Properly installing and connecting a 12 V diaphragm pump is important, both the electric wiring and liquid plumbing. As for the wiring and electronic aspects, it is fairly straightforward, but there are some key things to keep in mind.
First, although not required it is a good practice to put a fuse in your wiring harness. This will protect the wire. Second, when connecting your wire harness to the battery, make sure your clamps are secure. Cheap harness clamps or weak “alligator” clamps can bounce off if you are spraying over rough terrain.
One final consideration when wiring your pump, some larger 12-volt pumps draw more amps and may require heavier wiring to prevent overheating.
Fittings and Hoses
Connecting the plumbing is also simple, but it must be down properly to prevent issues. The suction line should be airtight. If air gets sucked into the line it will prevent priming. The suction hose should be at least as large as the inlet of the pump. A tube or hose with a smaller diameter can limit the flow of the pump.
Use a screen or strainer on the end of the suction hose that is submerged in the liquid. Although the pumps can handle small particles, it is important to filter out as much solid debris as possible. A 40-50 mesh screen like this is normally adequate.
A flexible hose should be used for the suction and discharge lines. These pumps vibrate and rigid plastic pipes can crack over time.
Some models have quick-connect fittings on the inlet and the outlet. These allow the pump to be removed more easily than the models with threaded ports. If a pump is bad or you want to remove it for winter storage, quick couplings allow you to do so without disconnecting lots of different pipe fittings and hoses. If your desired model does not come with these, you can always add a coupler like these male and female cam-locks.
Vehicle Connection
The power source obviously needs to be 12-volt DC. One of the best features of these pumps is that it’s possible to connect them directly to a vehicle’s battery. However, if you are using the pump when the vehicle is not running and keeping the battery charged, it can drain your battery. In that case using a dedicated power source, such as a deep-cycle battery, is recommended.
12-Volt Pump Maintenance
Regular maintenance will help to ensure the longevity of your pump. This means flushing the sprayer with clean water after spraying. If you are pumping a chemical, ideally you would flush it every time if possible.
If the pump will be stored for more than a couple of weeks, and you have been using it with anything other than water, use a tank cleaner/neutralizer to clean the pump and prevent any chemical attack on the diaphragm.
Winterizing your pump is important. In addition to flushing the pump out, you need to add antifreeze to the system if it is going to be stored somewhere with the potential to freeze. the pump itself can be stored indoors if drained and cleaned properly, but if the pump this part of a larger sprayer or they’re pumping system that cannot be stored indoors follow proper winterization guidelines.
Flow Rate and Pressure Adjustment
Although it is not required in every situation, it is common for a regulating valve to be used along with a 12-volt diaphragm pump. a regulating valve allows the user to control the pressure on the discharge side of the pump. This valve maintains the constant pressure by returning any excess liquid back to the tank or back to the suction side of the pump via a “bypass” or “relief” line.
A regulating valve is recommended when you have a demand-style pump. As we mentioned above it demand-style pump shuts off at a certain pressure. therefore if there is no regulating valve in place the pump can reach that pressure shut off and then start running again when the pressure drops. when this happens rapidly over and over it is called cycling. too much of this can be harmful to the motor and it will cause the pressure switch to wear out prematurely.
Adding a regulating valve allows the user to dial in the pressure keeping it constant and keeping the pump from cycling on and off. To see more about this topic and how to install a regulating valve make sure to read this article that explains pump cycling in more detail.
Troubleshooting
Knowing how to troubleshoot a 12-volt diaphragm pump is crucial for anyone who is operating one. It is an extensive topic and merits further discussion. I wrote an article that covers troubleshooting these pumps in great detail. Be sure to read it if you need help figuring out why your pump is not working:
How to Troubleshoot a 12-Volt Diaphragm Pump
Lifespan and Durability
The lifespan of a 12-volt diaphragm pump will vary greatly based on usage, maintenance, and the quality of the pump. Regular maintenance, proper storage, and following manufacturer recommendations can extend the pump’s durability.
It is hard to say what is the best brand of 12-volt diaphragm pump because I have not personally used them all. I can say that I have had good luck using Shurflo diaphragm pumps. The one I have used for the past few years on my sprayer is a 2088 series.
Conclusion
12-volt diaphragm pumps are very versatile and their relatively low cost makes them a great option for many different jobs. If you want to make sure they work properly in your scenario it is important to understand how they work I’m out of trouble shoot them. better understand 12-volt diagram pumps, measure to take a look at her other resources if you need more information.
