That’s an interesting observation. I’ve often wondered about that. I generally do try to be choosy about the plastic containers I use....
I suppose one could try to minimize such a situation in the tubing by trying to use “food grade” components/lines, and look for BPA-free assurances, but is that all worth it?
I don’t have drip irrigation (as yet) but I’m slowly replacing my garden hoses.... I keep my eyes open for hoses and tubing on Craigslist to see what kind of prices I’m looking at even discounted — I have seen coiled “lines” remnants from soda machines, hose from some kind of a bar remodeling, and once saw a length of BPA-free tubing that I think was for hydroponics (so may be it’s possible to find an entire system that is used in the hydroponics industry? Emitters sure used in some hydroponic set ups, too.)
What you said about exposed to the sun — I Imagine you could try to insulate or shade them from the sun a bit?
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