Anybody built an 8x40 RO?

[DocsMapleSyrup]

I'm curious if anyone out there has built an 8x40 RO unit for around 500-1000 taps. I'm planning to build an RO and can't fork out the money for a pre-built unit and it seems like making the jump from 2 - 4x40 membrane units to a single 8x40 unit is financially significant. What I don't understand is what the gain would be for the price paid in going to a larger unit. Anybody built one or have experience between the 4" and 8" units? Thanks for the discussion.

[ecolbeck]

I've never built one, but mathematically, doubling the radius of a tube will result in increasing the available surface area by a factor of 4. In other words, a single 8" unit would have the same theoretical capacity as four 4" units. Likely there are many other complicating factors....

[minehart gap]

The 8" membrane will allow for higher pressure also.