Quick answer: To stop sewn bags from leaking, work up this ladder: (1) fold the bag top over before sewing to minimize major leaks; (2) sew crepe tape over the top with a tape sewing head like the Empress Model 101 (or a crepe tape attachment on a handheld closer) for less leakage and a cleaner look; (3) use filler cord to fill the needle holes, or self-adhesive crepe tape to help keep moisture out; (4) if it's a fine powder that must not sift at all, switch to pinch bottom paper bags on the PBC 6000.
Dusty pallets, product trails across the warehouse floor and customer complaints about half-empty bags usually trace back to the closure. Here's why sewn bags leak and how to fix it, from free fixes to equipment upgrades.
Why sewn bags leak
- Needle holes. Every stitch punches a hole through the bag. Coarse products stay put, but fine or free-flowing products can work through.
- No fold-over. A single layer of bag material sewn flat gives product a straight path out.
- Poor stitch quality. Skipped stitches leave gaps. Pulling or holding the bag while the closer feeds is a common cause.
- Sewing in the wrong spot. Where you sew matters. The Model F manual says to sew 4 to 6 inches above the product and not more than four inches down from the top.
The leak-fix ladder
1. Fold the top over
A fold-over at the bag top minimizes major leaks. Bag-top folders are available as accessories for our Model 100 and Model 101 pedestal sewing heads.
2. Fix your stitch quality
- Let the closer feed itself. Don't pull the bag through or hold it back.
- Replace bent or dull needles and dull feed dog teeth.
- Set thread tension correctly. Improper tension can tear the thread.
- On pedestal heads, a two-thread Federal Type 401 double-locked chain stitch gives a more secure seam than a single thread.
3. Add crepe tape
Tape sew systems use crepe paper to enhance appearance and further reduce leakage. Your options:
- Empress Model 101 tape sewing head: sews crepe tape 1.25–2.5" wide on a conveyor line at 35–55 ft/min
- Model F: optional 2" crepe tape attachment for handheld closing
- NP-7A: crepe-tape binding and cutter assembly available by special order
4. Fill the holes or seal out moisture
Needle holes can be filled with filler cord, and self-adhesive crepe tape helps prevent moisture infiltration. Ask us which fits your product and bag.
5. Switch to pinch bottom bags
When product absolutely can't sift, like flour, bakery mixes or powdered dairy, sewing may never be enough. Pinch bottom multi-wall paper bags sealed on a PBC 6000 have no needle holes at all. Bag makers describe heat-sealed pinch bottom bags as sift-proof.
Which fix fits your product?
| Product | Usually enough |
|---|---|
| Coarse, large or pelleted product | Plain sewing with a fold-over |
| Granular product that dusts a little | Crepe tape sewing |
| Moisture-sensitive product | Self-adhesive crepe tape |
| Fine powder that must not sift | Pinch bottom bags on a PBC 6000 |
Frequently asked questions
Why do sewn bags leak?
Sewn bags leak mainly through the needle holes and the gaps along the stitch line. Fine or free-flowing products can work their way out, especially when the bag top isn't folded over or the stitch quality is poor.
How do I stop a sewn bag from leaking?
Start by folding the bag top over before sewing, which minimizes major leaks. For less leakage and a cleaner look, sew crepe tape over the top with a tape sewing head like the Empress Model 101 or a crepe tape attachment. Needle holes can also be filled with filler cord. For fine powders that must not sift, switch to pinch bottom bags on a pinch closer like the PBC 6000.
What is crepe tape on a bag?
Crepe tape is a strip of crepe paper sewn over the top of a bag as it's closed. Tape sew systems use crepe paper to enhance appearance and further reduce leakage compared with plain sewing.
What is filler cord in bag sewing?
Filler cord is a cord sewn in along the closure so it fills the needle holes, helping keep product from leaking through the stitch line.
Does crepe tape keep moisture out of bags?
Self-adhesive crepe tape helps prevent moisture infiltration at the bag closure.
When is plain sewing enough?
Plain sewing is ideal for larger materials that won't leak between stitches, like coarse or granular products, typically using one or two thread lines.
Can poor stitch quality cause leaks?
Yes. Skipped stitches leave gaps. The Model F manual warns that pulling the bag through, holding back the bag or machine, or pulling up on the machine gives poor stitch quality. Let the machine feed the bag, and keep needles, feed dogs and thread tension in good shape.
Still fighting leaky bags?
Tell us your bag material, product and how many bags you close a day, and we'll recommend the right closer. Call 866-888-6327 (Mon–Fri, 8am–5pm CST), email sales@clevelandequipment.com, or browse all bag sewers.