Filter Bag FAQ
What is a liquid filter bag?
A fabric bag — felt, mesh, or microfiber — that seats inside a bag filter housing and captures solids as liquid flows through it. Liquid filter bags are rated in microns, built to standard housing sizes 1–4, and are the lowest cost-per-gallon format of industrial liquid filtration. They’re distinct from dust-collection (baghouse) bags, which handle air. Browse the full liquid filter bag line.
What’s the difference between a size 1 and size 2 filter bag?
Same 7″ ring, different length: size 1 is 16.5″ long (2.2 ft² of media), size 2 is 32″ (4.4 ft²). They are not interchangeable — the bag must match the housing basket length.
When should I change a filter bag?
At about 15 PSID differential pressure across the housing, or on a time schedule if you don’t have gauges. Running far past 15 PSID risks rupture and particle unloading through the media.
Sewn or welded — which do I need?
Sewn costs less and suits most applications. Welded eliminates needle-hole bypass and thread, and is silicone-free — choose it for paints, coatings, inks, and any process where trace bypass or silicone contamination is a defect. See the sewn vs. welded guide or welded bags.
What does the micron rating mean?
For felt bags it’s a nominal rating (majority capture at that size, improving as cake builds). Monofilament mesh is a true geometric cutoff. Full explanation here.
Can filter bags be washed and reused?
Mesh bags, yes — wash out the cake and return to service. Felt bags are depth media; washing removes surface cake but not embedded solids, so reuse is limited and not recommended for critical service.
Which ring material should I pick?
Galvanized steel is standard and cheapest. Stainless for corrosives and food service. Polypropylene or nylon when metal contact is prohibited or the ring must survive aggressive chemistry — and plastic rings are fully incinerable with the bag.
What temperature can the bags handle?
Polypropylene to ~200°F, polyester to ~275°F, Nomex to ~450°F. Above that, talk to us about specialty media.
Do you make FDA-compliant filter bags?
Yes — FDA-grade polyester, polypropylene, and mesh with vendor certificates of conformance on file. Specify FDA grade when quoting.
What is a tramp oil filter?
Anything that removes free hydraulic and way oil from water-based coolant. The bag-format answer is an oil-absorbing (Oil Magnet®) bag: it binds tramp oil on contact while filtering solids, in a standard bag housing, with no skimmer or coalescer to maintain.
What is canton flannel filter media?
A napped cotton fabric — one of the oldest filter medias still in service, used for straining paints, varnishes, and plating solutions where the soft nap face polishes the liquid and releases cake cleanly. We sew canton flannel bags to order in any dimensions and top style.
Can you match a competitor’s part number?
Almost always. Eaton, Rosedale, FSI/Pall, Strainrite, Parker, Hayward, GAF and others follow decodable conventions — decode it yourself with our part number decoders, or send the number through the quote form and we’ll cross it to our equivalent.
What’s your minimum order?
Small. We’re a manufacturer that welcomes short runs — including one-off custom bags. Ask.