You fill more than 4–5 bags a minute
Choose a valve bag. At that speed the closure step in an open-mouth line becomes the bottleneck, and dust control gets harder the faster you fill.
Buyer Guide · Updated September 2026
Valve bag or open-mouth bag — how to choose
The short answer, the full comparison, and the three situations that decide it for most 20–50 kg dry powder lines.
Short answer: if your product is a free-flowing dry powder filled through a spout at speed, a valve bag will fill faster, create less dust and stack flatter. If your filling equipment is simple, your sizes change often, or your product is coarse or damp-sensitive, an open-mouth bag with a sewn or pasted bottom is usually more flexible and cheaper to run.
Both types are produced in our factory, so this is not a question of what we prefer to sell. It is a question of which one reduces your cost per tonne across filling, palletising, transport and returns. Here is how we usually decide it with a customer.
Comparison
Valve bag vs open-mouth bag, side by side
| Factor | Valve bag | Open-mouth bag |
|---|---|---|
| How it is filled | Through a valve, onto a filling spout | Through the open mouth, then sewn or pasted closed |
| Filling speed | High — designed for automatic and semi-automatic lines | Moderate — depends on the closure step |
| Dust and spillage | Low, especially with an ultrasonic valve | Higher; needs good extraction and a clean closure |
| Shape after filling | Flat and block-like, stacks neatly and holds its shape | Softer unless a pasted square bottom is used |
| Size flexibility | Made to a defined fill weight and spout | Very flexible, including odd sizes and small runs |
| Equipment needed | Filling spout and, ideally, a sealing or heat-seal option | Basic filling plus a sewing or pasting closure |
| Typical cost | Slightly higher bag cost, lower cost per tonne at speed | Lower bag cost, more labour or finish quality risk |
| Best for | Flour, putty powder, tile adhesive, pigments, dry mortar | Multi-wall flour sacks, sugar, starch, feed ingredients |
Decision Guide
Three situations, three answers
You run many sizes or small batches
Choose an open-mouth bag. It gives you freedom on dimensions and fill weight without changing filling equipment, which matters for custom and regional products.
Your pallets arrive leaning
Look at the bag shape, not just the ply count. Block-shaped valve bags stack flatter and resist shifting in a container better than soft, rounded sacks.
What We Build
Both types, one supplier
Because printing, tube forming and bottom making all happen in our workshop, we can advise on the structure and then produce exactly that bag — including the valve form, liner and reinforcement that match your filling line.
- Paper valve, inner/outer valve and ultrasonic valve constructions
- Sewn bottom, pasted square bottom and standing-bottom sacks
- 2–5 plies, 70–110 gsm per ply, with optional food-grade PE liner
- Perforated plies for de-aeration and flatter pallets
- Flexo printing in 1–8 colours
FAQ
Common questions
Is a valve bag more expensive?
The bag itself usually costs slightly more because of the extra valve construction, but the total cost per tonne is often lower on high-speed lines: faster filling, less spillage and pallets that survive the container.
Can I run a valve bag on a manual line?
Valve bags are designed for a filling spout. Without suitable equipment they are difficult to fill efficiently, so for manual filling an open-mouth bag with a sewn or pasted closure is normally the better choice.
Which is better for flour?
Both are used. Open-mouth sewn-bottom bags suit conventional flour sack filling; valve bags are chosen when the mill wants higher speed, less dust and flatter pallets. Compare the structures on our flour paper bags page.
Related: multi-wall paper bags, putty powder valve bags, laminated woven bags.
Not sure which bag your line needs?
Send a photo of your filling spout plus your product, fill weight and destination. We will tell you which structure fits and quote it.