I think I'll end up with a remote valve box near the water edge - the 1" line will feed that and I can fine tune the diffusers from there.
Interesting thought on the dump valve. Trying to build my own, I'm sure those kinds of things are already in the plug and play kits. So I'll add that to my parts list. The filters, check valves, pop-offs, gauges... they all add up pretty quick. I don't know that I'm saving much $ over a kit, but I am definitely learning more.
That chart is assuming 1cfm... I get a little fuzzy trying to do rough math on that. One diffuser @ 8', another @ 4. 1/2psi for every foot, so that's 6? 3-400' of 1" 'trunk' + valve box + 2 weighted 1/2" ~ 50' ... I should actually be able to push 3 diffusers if I wanted, so maybe I will want to waste a bit with two and even more when there's just one for the winter.
If nothing else, this has actually been kinda fun learning.
Thanks for your replies, Quarter Acre. We need a 'buy them a beer' button on here
