Are u wanting to do an autodrip system for the tank? If so u dont need the actual ro membrane. Can utilize the others tho for sediment and carbon. For general rule of thumb i drip 1gph per 100g for starters. Ur shooting for 100% or more tank volume for the week. I have a 450 at 4gph and a 500 at 6gph. Also have a 650 at 4gph. My stocks are low at this point tho i used to do 2gph for 100gal or more as needed for higher stocks.
K1 can be a bit confusing… its usually sold by the cubic foot. U can sometimes get a price break for buying more of it. Id estimate around 2 cubic feet of regular k1… I had 2cu ft in a 55g sectioned off in about that same size.
Ehh… that comes down to personal preference really. I glue mine in with primer 1st then glue as i would regular pipe but thats just me. A good tape can be just as good and permanent. I have 2 drip system supply lines running 24/7 at 40psi in house also that rely on tape and brass fittings. Ive had a cple of those fail over the yrs. Probably my fault tho for using too much tape and the brass fittings cracked over time.
Once again man can't thank you enough for all the help you have been throughout this! Sitting here in the garage trying to decide on what way to go with it that I won't regret later 🫤 I usually use slip fittings and glue them but I may have been a little less than sober when I ordered the new ones and got threaded instead 
Any time manAwesome brother!!
… Ive bought the threaded by mistake as well. I use a little bit of everything over here. Now that i think of it i have a dry pump running with tape and threaded fittings also 
… either way u go will be fine. I like the grey “fast tape” over the reg. white stuff. Seems to seal up better for me.Not sure I have work with the fast tape before. Is it available at like a box store like Lowe's or home Depot?Any time man
