Ro Unit Question

[elmo666]

Recently bought a small ro unit, 25 gpd. In hind sight probably a bit small. Thought about a booster pump, but water pressure is over 4 bar. What I'm wondering is how different membranes, 50, 75, 100 gpd give these amounts off the same water pressure? Is the water produced at a higher rate of the same quality?

 

[Lateral Line]

The larger the area of the membrane, the higher it's production will be at the same pressure, ie. a 2m2 will produce twice the volume, of the same quality as a 1m2, all other things being equal.

 

[elmo666]

Ok, that makes sense, but how does the larger surface area of the bigger membranes fit inside the same size cartridge? Or is it more a case that realistically, the smaller membrane could be housed in something alot smaller but chambers/cartridges are stanardised for mass production reasons?

 

[TwoTankAmin]

For any unit all you can change is the water pressure.A wider membrane wont fit.  My portable 3 dtage ro/di is 75 gpd max. I hook it to a sink faucet and push a reasonable psi into it (I mix in some hot to shoot for high 60s-low70s F). But it puts out more like 50 gpd give or take. iIfill a 20 gal. can and then store it in smaller containers- 6, 5, 2.5 and 1 gal cans as I have to move it around and store it in smaller spaces. I usually make water at the end of the week into the weekend so I replace what I use during weekend maint. and am ready for the following week as well. I can make two weeks worth that way.
 
Usually it takes a pump to get the max. output from any ro unit.

 

[elmo666]

Well, the supplier of my unit sells several membranes for it, all fitting within the same membrane housing, but outputs varying from 25 up to 100 gpd. I'm not questioning the science, just my inquisitive nature making me wonder just what the difference is and why they assure me that changing the membrane to a larger one will give greater output off the same source?

 

[TwoTankAmin]

Well I would take the word of the maker over mine.
 
There are a great variety of brands out there, so I am not sure what makes some of them different. This is the unit I have but when I bought it was about $100.
http/www.ebay.com/itm/Portable-Reef-Aquarium-Reverse-Osmosis-RO-DI-3-stage-water-filter-/270830509214?pt=LH_DefaultDomain_0&hash=item3f0ec19c9e

 

[Lateral Line]

In my unit, the membrane was rolled up. More turns on the roll, more area to work with. Thats one way I can think of doing it. Longer rolls is another. Guess it depends on the model.

 

[TwoTankAmin]

Yes. I know there are more different types of ro units than there are filters in this hobby. Mine was chosen because I have space considerations and could not have one permanently installed. I have not actually opened mine yet but am finally about to replace the carbon and ro parts. For some reason I assumed that the water was forced through a mebrane stretched across the flow path like one might use a screen. It would be a disk shaped thing.
 
I have learned something new with this thread, thanks guys