Net Weight vs Volumetric Fillers for Pails, Drums & Totes

In most real-world plants where density, temperature, and viscosity aren’t perfectly stable, net-weight filling is the safest way to hit targets, protect quality, and minimize overfilling. Volumetric filling can be excellent when filling small containers with stable fluid properties and environmental factors, but it needs tighter controls and more frequent checks to prevent inaccurate filling.

Net weight filling - Any pumping method with the container on load cells

• Measures the weight placed in the container
• High accuracy for pail, drum, and tote filling, depending on scale resolution and capacity
• Insensitive to density/temperature swings
• Maintains accuracy at high flowrates.  Works best with a pumping method that can slow to a "top-off" speed as we approach the target weight
• Less accurate when filling small bottles

Volumetric filling - Piston pump, PD pump, or flowmeter to measure fluid flow directly

• Measures volume (stroke counts, gear displacement, mag/PD/Coriolis meter, or timed flow)
• High accuracy for all container sizes, depending on pump sizing
• Assumes stable density/viscosity or requires compensation and K-factor checks
• Accuracy affected by wear, slip, entrained air, and temperature
• Higher equipment cost and/or slower flowrates when filling larger containers (ie drums and totes)
  
  

Bottom line: Net weight is inherently more forgiving for larger containers, but volumetric can be more precise for smaller containers.  Net weight is easier to keep consistent while volumetric requires consistent management of environmental factors and equipment calibration.

Which filling method for your operation?

• Density/viscosity/temperature can vary → Net weight
• Foam or entrained air → Net weight + sub-fluid-surface filling
• Large containers (5 gallon, 55 gallon, IBC totes) → Net weight
• Small containers → Volumetric

Contact us today to discuss which method is right for your operation.

FAQ

1. What’s the difference between net-weight and volumetric filling?
   Net-weight fills by mass using load cells under the container. Volumetric fills by volume using a piston, positive-displacement (PD) pump, or a flowmeter. Net-weight is generally steadier across temperature/density changes; volumetric can be faster and more consistent for small contains with stable/consistent fluids.
   
   
2. Is a Coriolis meter volumetric or mass?
   Coriolis measures mass flow (and can output density), not volume. It’s often grouped with “flowmeter fillers,” but technically it’s a mass-based method that doesn’t require a scale under the container. Many plants still add a checkweigher when using inline mass flow for large containers as a method of verifying the dispensed fluid amount.
   
   
3. When should I choose net-weight over volumetric?
   Choose net-weight if your product or environment varies (temperature, density, viscosity), if you fight foam/entrained air, or if packages are large and product is costly. Choose volumetric for small containers at high speeds under tightly controlled conditions.
   
   
4. Which is more accurate in real-world conditions?
   Net-weight is usually more robust because mass doesn’t change with temperature or aeration. Volumetric can be very accurate too, but it’s more sensitive to viscosity, slip, entrained air, and temperature expansion.
   
   
5. What accuracy can I expect?
   With a net-weight system, pails, drums and totes can be held within ±0.1–0.2 lb with well-tuned systems. Volumetric accuracy can be more precise but will vary greatly between different filling systems (such as diameter of the piston in a piston filler).
   
   
6. How do I size load cells and scales?
   Pick capacity for gross load (container + pallet if palletized + product). I good practice would be to aim for 2–3× the typical net fill to avoid overloading the load cells. Choose resolution/divisions that give you the smallest practical increment without significant noise.
   
   
7. What pumps pair well with net-weight?
   Use pumps that provide steady, controllable flow: gear, lobe, and diaphragm are some examples.  It's generally necessary to have at least two speeds- fast during the majority of the fill and then slow as we approach the target weight for accuracy.  Electric pumps should ideally be 3-phase and used with a variable speed control (like a VFD).  Air-operated pumps should be used with a 2-speed pneumatic control or proportional controls for true variable speed. 
   
   
8. What do I do to calibrate a filling system?
   For net-weight: tare/zero for every fill cycle plus periodic test weights to verify accuracy. For volumetric: scheduled K-factor/stroke checks, density/temperature compensation checks, and wear inspections on pumps/valves.
   
   
9. Why do volumetric systems “drift”?
   Temperature changes expand/contract volume, viscosity changes cause slip, entrained air looks like extra volume, and mechanical wear changes displacement. Good preventative maintenance, temperature control, and periodic recalibration will help keep the system accurate.
   
   
10. Do I need legal-for-trade components for a net-weight filling system?
    If you sell by weight to a customer, you may require NTEP approved “legal-for-trade” components and procedures per jurisdiction. If you fill by net weight and then sell by volume (ie your customer purchases a 5-gallon pail), then NTEP "legal-for-trade" is not required.
    
    
11. Are sanitary/washdown designs compatible with net-weight?
    Yes. choose suitable stainless frames, protected load cells, and IP-rated instrumentation. Keep cabling and junctions out of direct spray where possible, and validate sanitation procedures don’t compromise scale stability.
    
    
12. Does volumetric filling work with heated fluids?
    Yes, but you will need to implement temperature compensation when you're determining initial fill volume of your heated fluid. Volume contracts as temperature drops so the same mass occupies less volume.