Which RO Membrane

[birdman1979]

Can I put a 75gpd membrane in my my ro canister? It originally came with a 100gpd membrane.

 

[sedor]

I wouldn't. Why not just buy the proper one?

 

[birdman1979]

Good call. I'll just use the right one.

 

[OCRick]

You can, but you will have to change the flow restrictor...depending on the membrane the 75gpd may also get you a better rejection rate.

 

[Buckeye Hydro]

You bet. The RO Membrane Housing on nearly all RO systems is a standard size for what are called "1812" membranes (1.8 inches in diameter and 12 inches in length). As mentioned above, if you go down to a 75 gpd membrane you'll get better rejection (i.e., cleaner water from the membrane), but at a bit slower pace than you see from your 100 gpd. Your DI resin will last longer.

Also as mentioned above - you'll need to install a matching flow restrictor - a very inexpensive part that you can install in 30 seconds.

Russ @
Buckeye Field Supply

 

[aquaman67]

+ 1 above post.

Make the swap. You'll save on DI resin because 75 gpd membranes are far better than 100 gpd.

An average mixed bed DI cartidge should process about 5000 ppm/gallons of ionic load. If all of your load is measurable as TDS on the meter you are using then if your RO membrane is putting out 6 ppm TDS at 98% rejection then it would process about 5000/6 or about 833 gallons. If your membrane has gone down to 96%, then with 5000/12 or about 416 gallons (HALF the DI life). This is why a 4% loss of rejection performance is a big deal. Continuing this example, a 4% loss would be 5000/18 or about 278 gallons (a third of what you would get for lifetime if you had a 98% rejection membrane).

 

[Toddrtrex]

In addition to above, you might not see that much of a drop off in how much water is made, at least not enough to be an issue. I have a 75 GPD membrane and with my pressure and temp (( 60 PSI, 68* )) I can still fill up a 5 gallon container in 2 hours.

 

[Buckeye Hydro]

There is a calculator available where you can estimate production in gallons per day based upon your membrane capacity, water temperature, and water pressure.

Russ