[Navy salad]

I was reading an article here: https://sectionhiker.com/how-to-clean-sanitize-and-store-a-water-filter-in-the-off-season/ talking about doing a bleach sanitizing to clean water filters, something I assume most people here are already familiar with. But at the bottom of the article there was a comment by "Odd man out" on the use of vinegar to remove hard water minerals. Since the mineral salts are basic, and the vinegar is acidic, flushing the filter with the vinegar will chemically dissolve and remove the mineral salts and help restore water flow. In a nutshell, his method is to flush the filter several times with distilled vinegar, and then fill it again with vinegar and let it soak for an hour or so. I did this on my Versa Flow water filter and could see the bubbling reaction from the vinegar and dissolved minerals, almost like vinegar and baking soda, which wouldn't have happened if there weren't any mineral salts for the vinegar to react with. After the hour is up, flush it with distilled water several times until you can no longer taste vinegar. I let my last water flush sit for an hour, which seemed to do a good job getting rid of the last trace of vinegar. My water flow was noticeably quicker after this.

[Randito]

The important follow up test is to try filtering some water containing 5 micron particles and inspect the output to ensure that no particles larger than 5 microns are present in the filtered output. The vinegar might have an effect on the pore size of the filter after all. Giardia are 10 to 20 microns in size -- if the vinegar enlarged the pores in the filter and let them through -- not fun.

[Navy salad]

What substance are you referring to that has consistent, and harmless, 5 micron particles to test with? And then once you've intentionally introduced 5 micron particles into the filter, wouldn't you then have to re-backflush the whole thing to get that substance back out? Vinegar works not by force, but by simply dissolving the otherwise-insoluble mineral salts so they are flushed out with the water/vinegar solution, so as such it's actually more gentle than doing a back-flush, which relies on forceful water pressure to expel contaminants. Since household distilled vinegar is a very mild acid that we even use in salad dressing, it's unlikely to damage any filter membranes which are typically made of hollow fiber membranes (plastic-like polymers) that do not dissolve in vinegar.

[Randito]

How do you know that acetic acid doesn't enlarge the pores in the filter? Different brands / models use different materials. Some are likey fine, but some may not be. A responsible manufacturer will have tested various methods of cleaning the filter and use the test results to formulate the care recommendations in the filter user's guide. The guy recommending using vinegar may have had good results with his brand/model of filter in water in his region, but those results may not apply to all filters in all regions. When it is a matter of life safety, isn't it better to stick with the manufacturer's tested recommendations?

[Navy salad]

The most common hollow fiber materials supplied by 3M to filter manufacturers are polypropylene, polyethylene and nylon, all of which are highly resistant to most chemicals even far harsher than household vinegar. But my guess is you won't find that persuasive, since that doesn't prove any of these are the fibers being used in a given filter. Sawyer specifically recommends using vinegar, both in the FAQ section of their international website and in this video . Sawyer really emphasizes using forceful water pressure for a routine backflush. If I had to worry about enlarging my filter pores, "forceful backflushing" would be at the top of my list! In addition, the user manual for the Hydroblu Versa filter I own suggests the use of vinegar for improving water flow that has been reduced by mineral deposits. I also read more anecdotal evidence of people calling the customer service lines for PUR, Katadyn, and MSR filters for flow problems and being told to try vinegar. Seems like an odd thing for someone to missreport, so I would find this pretty credible. And if you search around, you'll find plenty more "How to" articles that suggest this option for clogged filters.

[hbb]

I'm not a chemist, but I find it hard to believe the the molar concentration of acetic acid in household vinegar is sufficient to dissolve the polymer used in hollow fiber filter membranes. I mean, it's not like the gallon jugs of vinegar you see in the grocery store use some high-end material, they are about as cheap as they come. Edited to add: I've had a gallon jug of white vinegar in my pantry for about 8 years. It's just Type 2 HDPE.

[Randito]