How to select the right pump?

The basics for choosing the right pump to use with a Fluid-Bag

Here is some advice from Fluid-Bag for choosing the right pump for getting your liquid out of the container, and into your manufacturing line. There are some basic facts and aspects you should always consider when you need to buy a new pump or find a replacement pump. 

Here below are the most important things you need to find out to select the best pump for your application. This is the same information that the pump or machinery supplier will ask for, to be able to suggest a suitable pump option for you.

1) Liquid properties

Fluid characteristics

What are the chemical components of the fluid you plan to pump? This is useful information to avoid abrasion or corrosion, or to consider other aspects that might affect what materials can be used in the pump and in the adaptors, seals etc. It’s also useful to know if the liquid contains solid particles, how large etc. This information can usually be found in the liquid product’s Material Safety Data Sheet (MSDS).


Is your product thick and pasty, or is it a very liquid fluid? A high viscosity means that the liquid is thicker, and it usually means that a more robust pump is needed. This information can also be found on the Material Safety Data Sheet (MSDS). There are different units for expressing viscosity, but the most common one is cP (centipoise).


How warm or cold will your product be when it is pumped? This will affect fluid characteristics such as viscosity, and it will also affect which pump materials are the best fit.

2) Flow rate

Answers the question “how much liquid is flowing from the pump in a given amount of time”? This is measured in liters per minute or gallons per minute. In other words, how quickly do you need to get the product pumped out of the container? In general, you can say that for a higher flow rate you need a larger pump diameter measurement / a larger pump size.

3) Pressure

What is the required pressure at the inlet and outlet of your pump? This information is important and contributes to deciding the pump size and type. The required pressure will be affected by how far you need to pump the liquid, the tubing diameter, bends and height differences in the piping, and what the required pressure is at the machinery that will receive the pumped liquid etc. If you don’t have this information on hand, you can check the requirements of the production line/machine where the liquid will be used.

Understanding the relation between pump flow rate and pump pressure

Generally speaking, you always choose between a higher flow rate or a higher pressure. If you need more of both, the answer is getting a bigger size pump.

This relation can be read and understood from the pump suppliers’ specifications. As an example, we explain the ratio of 3 different models of Graco grease pumps:

Graco Fireball 425 - 10:1

  • For 1 bar input pressure, you get 10 bars of pressure out of the pump.
  • In this case, with this pump model, the flow rate is 19.7 liters per minute.

Graco GT 750 - 36:1

  • For 1 bar input pressure, you get 36 bars of pressure out of the pump.
  • In this case, with this pump model, the flow rate is 14.5 liters per minute.

Graco Fireball 425 - 50:1

  • For 1 bar pressure, you get 50 bars of pressure out of the pump.
  • In this case, with this pump model, the flow rate goes down to 1.9 liters per minute.
  • In this case, the pressure is much higher so the liquid product will continue to move even though the distance might be longer, or there are bends or thinner pipes along the way. On the other hand the speed (flow rate) will be much lower.

Note: the flow rates are only examples to illustrate the ratio, the actual number will depend on the product you pump, temperature and other factors.

The most commonly used pumps with Fluid-Bag

- Piston Pumps
- Diaphragm / membrane pumps
- Progressive cavity pumps

Further information:

We have also prepared a longer checklist of details to consider when choosing a pump. This is a comprehensive list to help you figure out your needs and to inform either your packaging/machinery supplier or your pump provider about your requirements.

You can download the checklist by filling out this form: 


You might also be interested in examples of pump set-ups we use in the Grease segment

Click on the image below to go to the download form for getting 3 pump set-up examples:

Fluid Bag Grease Pump Guide banner2