Quick question regarding flood tables and res size

Hi There. I've been cruisin around the forum for quite a while now and think y'all are the shit. Just about to get my first grow goin.

I've got a 5x10 secret jardin and I'm looking to put 4'x8' grow tray in it.
Or
two 4x4 trays, I'm kinda leanin towards the second one.

Anyways my question is:

Is a 70 gal res enough for a 4x8 tray? I know it varies depending on how I set my tray up but I need to know beforehand so I can make sure it gets set up right. right? (no need for an answer here)

The reason I ask is because I found a really good deal on a 70 gal res on craigslist. If that's not going to work I'm going to buy two 40 gal res and 2 4x4 trays.

I plan on using net pots filled with and surrounded by hydroton. SOG style.

Any help is very much appreciated.

Thanks beforehand

40 gal is alright for 4x4, 50 gal is better, 70 gal is good for up to a 3x6 (I have one for my two 3x6 flood trays I flood at separate times). You should get at least a 100 gal for you 4x8.
Lets do the math, 1 cubic inch = .004 gal
48"x96"x5" = 23,040 cubic inches x .004 = 92 gal

A tray holds at max 6-7" of water and typically 4x8 tables are a little smaller then that interior dimensions, so you could prob get away with a 80 gal but you would have to top it off a lot.

Hey Bezy. Thanks for the response, much appreciated. I ended up getting a 70 gal rez and one 4x4 tray. I plan to get one more and alternate floodings, like your setup. +rep