Our well has visible sediment and the water is dingy, unfiltered. So I have two large filter canisters in series, 1" piping. The first has a 50 micron element and the second has a 5 micron element. My idea, whether it is correct or not, is that the first filter will catch some of the sediment and thus prolong the life of the second element, increasing the time between filter changes. The cartridge manufacturers specify a replacement schedule-- but they have a vested interest in selling lots of cartridges! The first filter also supplies the outside faucets so that the coarser sediment does not clog nozzles and sprinklers. Water for the clothes washer and for other in-house uses also goes through the 5 micron filter. So I replace mine when the drop in pressure becomes too great. And that has proved to be about every 10-12 months. I see no reason to change that plan.

If I may jump in before Silica returns, Vladimir, I would say that particle size, durability, and porosity affect the amount of oxygen in the root-zone. Particles that are appropriately sized will create spaces within the mix; if the particles are durable, they will hold those spaces open without collapsing; and if the particles are also porous they will allow oxygen to return to the root-zone sooner by taking and giving up their moisture more efficiently. Josh

I think the first question is going to be - what are you hoping to use it for? I ask because some mixes are pretty much 'sterile' already, and perform just fine. However, even though many people apply the term 'sterile' to planting mediums, it should be noted - just for accuracy's sake - that it's almost impossible to sterilize soil without extremely harsh chemicals, or equipment not available to the average person. The closest that the average person can come is sanitization, and to keep it that way is next to impossible. Many products used to create mixes are - barring contamination - pretty much 'sterile'. Vermiculite and perlite are examples. Another issue that your post addresses is this issue of mycorrhizae. Now, it's true that some plants can form symbiotic relationships of this type, and there's no doubt that fungi (as well as other soil life forms) do play an integral role in the cycles that affect plant growth in nature, but these relationships are not necessary at all. This is why I asked about what will be your use of the potting soil. If it's for container plants, don't sweat the issue. There's a lot of hype surrounding mycorrhizae because it's one of those new products for which companies are trying to establish a market. Plants have been growing in containers for millennia. No special products necessary. This isn't to say that some things help more than others, it's to say that spores are EVERYWHERE! Wait... you just breathed in a thousand of them lol. If you want to grow a tropical plant, for example, then odds are that any mycorrhizae that have a relationship with that plant will only thrive in the tropics. The products that are sold as mycorrhizae only contain a few species, and doubtfully those for tropical plants. So... 'sterilization' of soil is really only important for those people who don't want to introduce bugs or diseases. And if you haven't experienced these problems, it's not really an issue. If you are running a commercial operation, and you want a good reputation, then finding a 'sterile' (sanitized) mix may be more important to you.

I don't think so. Even if all is well at The Treatment Plant, there is so much that water can be exposed to between there and your kitchen sink. Especially if your home, or the water lines that deliver the water TO your home, are older than just a few years. We cannot afford to depend upon the EPA to protect us from water contamination, or anything else for that matter. There are so many contaminants in our water that they don't consider to be unsafe. But, here in America, Land of the Free and Home of the Brave, shouldn't we have the right to choose? If you do much reading about things that are done "for the public good", you will soon run into many who consider the addition of fluoride into our water supply as a bad thing. Here is a link to some interesting information about that, presented at Dallas City Hall by Dr. Paul Connett in 2014: https://www.youtube.com/watch?v=xguPD85-BH4 Not to mention how difficult it is to find toothpaste or mouthwash that doesn't contain fluoride. Not to mention that fluoride is not the only intentional contaminant in our tap water. There's chlorine added to kill bacteria. When we water our garden from our home's water hydrant, we are contaminating our soil and therefore our plants, with whatever's in that water. We are also discouraged from disposing of any of our pharmaceuticals by flushing them because it has been found that some of these drugs do not process out. It is folly to trust that NOBODY is flushing drugs. Seriously, there is a large population in America that either doesn't know, doesn't believe, or doesn't care. Even if you have a septic tank, where do you think the septic tank truck goes when it's full? For a long time, we felt safe drinking water that was filtered. And then, we found out that there are not many filters that can remove anything beyond particulates. So many of us started buying bottled water. Now, we are hearing that certain elements of the plastic that the bottles are made of are getting into the water that's in the bottle. Not to mention that our landfills are now littered with them. Also, not to mention, that what's shown on the bottle label as "spring water" is now said to actually just be tap water from some other place, we know not where. When we lived in town, I bought a water distiller. This was because the small town in which we lived was in the habit of flushing the lines every now and then. We'd do a load of wash and find our white clothing washing in rusty-looking water. We'd fill a glass with water at the tap and it would be brown, sometimes with stuff in it that would settle to the bottom of the glass. And I still use the distiller, now that we live in the country. When the distiller is finished, I find about a tablespoon of dark brown liquid in the bottom, and it stinks. And there's a coating of lime on the whole inside, where the water boiled as the steam fed into the evaporator coils. I've read that the only way contaminants can be dependably removed from water is via steam evaporation or by reverse osmosis. Even this is not a perfect situation. It takes time to do. But at least I'm not lugging home case after case of bottled water. There's the cost of the distiller, but it pays for itself eventually if it replaces bottled water. There are some who say that, once it's distilled or "osmosed", the water is "dead": devoid of any of the trace minerals that we need to have in our water. So what are we to do? Why, we buy Trace Minerals, and we put 20 bitty drops of it in each gallon. Can we trust the efficacy of these Trace Minerals? I don't know. It seems like everybody lies to us now. And it is sold to us in a plastic bottle. *Sigh*.