[drewnoakes]

I'm curious to know how stable the blend of elements in tap water is. Do you have any data around this?

I once used an inexpensive electrical TDS meter (total dissolved solids) to track the amount of non-organic solids in water both before and after filtering over time. My goal was to determine the rate at which to replace the filter, and it turned out the manufacturer's recommendation was perfect. However I did notice that the unfiltered water's measurement fluctuated a lot over time. Could that pose a challenge in your scenario?

Thanks for a great read, btw.

[lathyrus_long]

I have a drain-to-waste system running open loop, with a constant dose of acid and sensors monitoring the pH of the leachate that drains from the pots. In that system, I've seen step changes in that pH that I believe correspond to step changes in my source water, perhaps when my utility changes which wells supply me. Hard to say without a detailed water analysis, but I'd guess the changes in nutrient profile (e.g., ppm Ca) aren't too important, and that as long as I adjust the acid dosing to maintain target pH the plants won't be affected much.

A single well may also show gradual seasonality, like from snowmelt and such. I assume that's happening too, but in my current setup that would be hard to distinguish from gradual pH variation due to changes in the plant nutrient uptake.

[chana_masala]

Wow, do you have more resources for the drain to waste system?

[lathyrus_long]

Nothing exciting--the plants drain into a 1020 tray, and a pump sucks up the leachate. The pump feeds into a waste bucket, through a sample cup that contains pH and EC electrodes. (It would be more common for the leachate just to drain by gravity, but the pumps made best use of my limited balcony space.)