Using RO to purify…. Water?

[82cabby]

Hi gang-

I have a 4x150gpd and a 5x400gpd homemade ROs. Any reason I can’t replumb the 150gpd so the permeate goes to the next membrane in the series instead of the concentrate and run it to really really purify well water?
I need to generate a lot of permeate to flush the ROs, store the membranes, etc and the spigot for the well water is right next to the ROs. The 150gpd is easier to replumb than the 400gpd.

[wobbletop]

Wouldn't work. You could try running it through twice though.

It's probably already pure enough... get a TDS meter and test it.

Also, you'd have to pressurize the concentrate line of the 2nd RO which would pressurize the permeate line of the first RO, and would wouldn't make any permeate.

[82cabby]

Wouldn't work. You could try running it through twice though.

It's probably already pure enough... get a TDS meter and test it.

Also, you'd have to pressurize the concentrate line of the 2nd RO which would pressurize the permeate line of the first RO, and would wouldn't make any permeate.

I’m sorry, I don’t think I explained what I’m thinking very well. I’m not suggesting connecting the two machines in series. I’m wondering if on the machine with 4 150gpd membranes I can connect the permeate out of membrane 1 to the input of membrane 2… etc. Then gang up the concentrate lines (the way we do usually with permeate) and put the needle valve there.

My well water has lots of iron, etc in it. I can’t use it as is.

[82cabby]

Ok, I’m an idiot. After much testing here’s what I figured out:

The well water coming in is about 140 ppm total dissolved solids. (It’s not our drinking water). With the RO hooked up the way I described it output about 3 ppm TDS. BUT very slowly. No way I was going to get enough permeate to do what I need in less than a day and a half! Then I realized why I’m an idiot. 150 gpd membranes, in series, it’s gonna be slow.
SO, I connected them in parallel and now I’m putting out WAY more volume and TDS only raised up to 10 ppm which is low enough for what I need.

Brain wasn’t working properly for a while there!

Edit: TDS dropped to 2 after producing about 12 gallons of permeate so I guess the membranes are benefiting from the rinse too!

[Pdiamond]

When I have those brain fades I drink more coffee.