I use the RV filters outdoors for my vegetable gardens. Some is raised bed. Some is in the ground. It's a variety of fruits and veggies and this year, no cannabis (I have an abundance) so yes, you can use these outdoors. In some areas, the calcium levels are so high in well or even municipal water supplies, its a cheap way to address this. Being in ground does make it harder for it to build up in the soil, but it still can over time.
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