help me setup drain to waste coco please?

Okay so I've been considering running drain to waste coco to get my feet wet in something other then organics. I luckily already have a pit/drain located in my my space that deals with washing machine water/couple other things..its not a shit pit so none of toilets connect to it . I also have access to water line that I can cut into less then a foot away. I have a couple of questions maybe you guys can help with?

1) Im about to test my tap water, if it comes back high ppm Im going to have to use RO...would buying water from the machines at the store kill me for drain to waste?If so whats a decent RO filter gonna run?(I'm only gonna setup a 3.5x3x7 out of my grow room for coco)

2)Would I be able to get away with a food grade 50 gal barrel as a res?

3) I need general help/links from anyone that wants to contribute information to point me in the right direction on the drip irrigation that I'm going to need to setup.(hardware,knowledge)

Ahead of time I am going to be doing research/have been for a while but I'm just looking for some feedback from anyone that has experience and wants to drop a bit of knowledge to a newb

You could use an undersink cartridge filter, no absolute need for the
RO to start, in my opinion.

I recall that every grower who used bottle water regretted it sooner than later,
not the cost, but the process of lugging 10 5G bottles every few days.

Guessing 50 gal res for your needs will be okay, my res is 1.25G, lol

Some say wide open lines with inline valves per feedline,
some like the GPH drippers for even pressure.

Set a budget and draw up a shopping list.

Look around the threads here on icmag, it will hone your
ability in research on this site and allow you to establish
good lines of communication with folks here on the threads.

Here's a good thread:

https://www.icmag.com/ic/showthread.php?threadid=241341

Welcome aboard.