Do RO membranes "break in"?

Jimmer12 · 11/09/2015, 02:04 PM

I just fired up my rodi system and bought a dual inline tds meter. I'm calculating my rejection at 96.5%. This is with a brand new dow filmtec 75 gpd membrane, I was under the impression that dow membranes were 98% efficient. Anyway should this improve as it breaks in or should I just be satisfied with this rejection?

shifty51008 · 11/09/2015, 02:10 PM

96-98% so your fine, if you want a true 98%+ membrane you will need to look at hand tested membranes like the maxr membrane from buckeyehydro, and spectrapure also has one.

Water pressure, and temp can help the membrane also.

Jimmer12 · 11/09/2015, 02:21 PM

Ok thanks for the reply. I've got a booster pump on the system so pressure should be fine, incoming water is pretty cold up here so that may be affecting things then.

Vinny Kreyling · 11/09/2015, 05:34 PM

Cold water definitely will affect performance.

Buckeye Hydro · 11/15/2015, 06:07 AM

Water below 77F will INCREASE the rejection rate, but slow down production.

And yes - membrane performance improves in the first 6 to 24 hours of run time.

Russ

Jimmer12 · 11/15/2015, 08:22 AM

Thanks for the info Russ. I haven't had it running for 6 hours yet but rejection rate has consistently been around 97% so it's looking good so far.

Buckeye Hydro · 11/15/2015, 09:18 AM

97% is not uncommon. Sounds like you're fine.

11/09/2015, 02:04 PM	#1
Jimmer12 Registered Member Join Date: Nov 2013 Posts: 188	Do RO membranes "break in"? I just fired up my rodi system and bought a dual inline tds meter. I'm calculating my rejection at 96.5%. This is with a brand new dow filmtec 75 gpd membrane, I was under the impression that dow membranes were 98% efficient. Anyway should this improve as it breaks in or should I just be satisfied with this rejection?

11/09/2015, 02:10 PM	#2
shifty51008 12-5 Chiefs record Join Date: Mar 2010 Location: NW Iowa Posts: 10,134	96-98% so your fine, if you want a true 98%+ membrane you will need to look at hand tested membranes like the maxr membrane from buckeyehydro, and spectrapure also has one. Water pressure, and temp can help the membrane also. __________________ 75 gal. mixed DT, 100 gal. sump, 50 gal. fuge, Clownfish breeder

11/09/2015, 05:34 PM	#4
Vinny Kreyling Registered Member Join Date: Nov 2002 Location: Miller Place, NY Posts: 7,206	Cold water definitely will affect performance. __________________ 250 gallon mixed reef, 2 Reefbreeder's Photon V 2, Deepwater BLDC 12, DAS EX-3 Skimmer, MTC mini cal, 2-3/4" Sea Swirls, Aquacontroller & 6 Tunze pumps.

11/09/2015, 02:21 PM	#3
Jimmer12 Registered Member Join Date: Nov 2013 Posts: 188	Ok thanks for the reply. I've got a booster pump on the system so pressure should be fine, incoming water is pretty cold up here so that may be affecting things then.

11/15/2015, 06:07 AM	#5
Buckeye Hydro .Registered Member Join Date: Sep 2006 Location: Cincinnati, Ohio Posts: 4,857	Water below 77F will INCREASE the rejection rate, but slow down production. And yes - membrane performance improves in the first 6 to 24 hours of run time. Russ

11/15/2015, 08:22 AM	#6
Jimmer12 Registered Member Join Date: Nov 2013 Posts: 188	Thanks for the info Russ. I haven't had it running for 6 hours yet but rejection rate has consistently been around 97% so it's looking good so far.

11/15/2015, 09:18 AM	#7
Buckeye Hydro .Registered Member Join Date: Sep 2006 Location: Cincinnati, Ohio Posts: 4,857	97% is not uncommon. Sounds like you're fine.