304 vs 316 Stainless Steel Filter Housing: How to Choose
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Short answer. For most fresh water at normal temperature, a 304 stainless steel filter housing is enough. Choose 316 when the liquid has more chloride (salty or brackish water, some well water, brines), when you use chlorine or chloride-based sanitisers, or when the liquid is acidic and you want a margin. 316 costs more, and in our store most 316 housings are made to order; each product page shows the current price for your country. Browse stainless steel filter housings in both grades.
304 vs 316 stainless steel: what is the difference?
Both are austenitic stainless steels. 316 adds about 2–3% molybdenum, which makes it more resistant to pitting and crevice corrosion from chlorides. Filter housings have crevices by design (gaskets, threads, clamp seats), so chloride resistance matters more here than on a smooth pipe.
How much chloride is too much?
Published guidance for natural and drinking water (pH 6.5–8, normal temperature) gives these approximate limits:
| Grade | Crevice corrosion rare below | Conservative limit for unfavourable conditions |
|---|---|---|
| 304 / 304L | about 200 mg/L chloride | about 50 mg/L |
| 316 / 316L | about 1,000 mg/L chloride | about 250 mg/L |
Above about 1,000 mg/L chloride (seawater is far higher), neither grade is a safe default; higher-alloy steels or non-metal housings are used. Source: Nickel Institute, Stainless Steel for Potable Water Treatment Plants (No. 10087).
Free chlorine is a separate question. For continuous exposure at about 20 °C and neutral pH, the Australian Stainless Steel Development Association gives roughly 2 ppm for 304 and 5 ppm for 316. Higher temperature lowers these limits, and neither grade is recommended in chloride service above about 60 °C because of stress corrosion cracking.
These are general guidelines, not a guarantee for your system. Your water analysis, temperature, cleaning chemicals and how often the housing is drained all change the answer.
Quick guide: which grade for which liquid?
| Your liquid or situation | Usual starting choice | What to check |
|---|---|---|
| Mains water, RO pre-filtration, cooling water (low chloride) | 304 | Chloride level of your water |
| Well or bore water | 304 or 316 | Get a chloride test first |
| Brackish water, brine, salty process water | 316 at least, often a higher alloy | Chloride level and temperature |
| Water with continuous chlorine dosing | 316 above about 2 ppm free chlorine | Dose and temperature |
| Beer, wine, cider | Often 304; 316 if your sanitisers or water are high in chloride | Cleaning chemicals, temperature, sanitary fittings |
| Kombucha and other acidic drinks | Ask us with details | Acidity, contact time, sanitisers |
| Hot liquids above 60 °C with chlorides | Neither by default | Ask us |
Beer and kombucha: what we need to know first
We cannot say a housing suits a brewing line without knowing the conditions. Send us:
- What is being filtered (wort, finished beer, kombucha, rinse water) and at what stage.
- Temperature during filtering and during cleaning.
- Your cleaning and sanitising chemicals, their strength and contact time.
- Whether your site requires sanitary design (tri-clamp ports, polished surfaces, certified materials).
- Flow rate, the solids you need to remove (yeast, hops, fruit, sediment) and the micron level you are aiming for.
Fine filtration of beer or kombucha can block a filter quickly, depending on the yeast and solids load. The micron rating, the filter area and a coarser pre-filter decide how long a filter lasts, so we will not promise that a filter will not block. For tri-clamp lines, see our sanitary tri-clamp filters.
The housing grade is not the whole story
- Seals. SUS304 or SUS316 describes the housing body. Gaskets are separate; we offer silicone, EPDM, FKM and PTFE for 2.5 in housings. Choose the seal for your liquid and temperature too.
- Fittings and valves, such as the drain valve, may not be the same material as the body and may not be stainless steel. A 316 housing means a 316 body, not that every part is 316. Ask us before ordering if this matters for your application.
- 316L is the low-carbon version of 316 and is preferred for welded parts. Ask us which version a given housing uses.
What 316 costs
A 316 housing costs more than the same housing in 304, and the gap depends on the product and the country you order from. Check the current price on each product page:
| Housing | SUS304 | SUS316 |
|---|---|---|
| 2.5 in threaded housing with drain | In stock, listed price | Made to order, listed price |
| Jumbo 4.5 in clamp housing | In stock, listed price | Made to order, listed price |
| Bag filter housing #1 / #2 | Listed price | Quoted separately |
FAQ
Is 316 always better?
It resists chlorides better, but it costs more. If your water is low in chloride and you do not dose chlorine, 304 is the usual choice.
Can I use a 304 housing for seawater?
No. Seawater chloride is far above the published limits for both 304 and 316.
Does 316 make the filtration finer?
No. The filter rating comes from the cartridge or bag, not the housing.
How do I find my chloride level?
Your water supplier's report usually lists it. For well water, a lab test gives chloride in mg/L.
Not sure which grade you need? Send us your liquid, temperature and cleaning chemicals and we will suggest a housing. See also the filter cartridge size guide.