Which RO Membrane is better?

[reefinginLA]

Costs aside, which would give me the best water quality:

1. Kent Marine Hi-S TFC Membrane or

2. Dow Filmtec

Looking to replace my membrane in my Kent Marine R/O unit.

Thanks!
Ferd

[rbursek]

I have th HiSTFC in my unit it is the original that came with it, but all I read here is the Dow Filmtech, maybe the Rat will chime in, I did not know what was all out there when I bought my unit, did not know about RC then.

[jeffhaag]

Use a TDS meter to check the quality/life of your filters. All things aside, as long as you have DI after the filter, there shouldn't be any difference.

[rbursek]

Wrong, there is a difference in RO membranes!

[RichConley]

Originally posted by rbursek
Wrong, there is a difference in RO membranes!

Reread his post. As long as there is DI, the water will be almost exactly the same membrane to membrane, which is what he was saying. The big difference is that DI will last much longer with a better membrane.

[rbursek]

I understand the DI will make up the difference but there is differences in membranes, that is all I was trying to get across, and with a better membrane your DI resin will last longer.

[reefinginLA]

Originally posted by RichConley
Reread his post. As long as there is DI, the water will be almost exactly the same membrane to membrane, which is what he was saying. The big difference is that DI will last much longer with a better membrane.

Thanks! So then as I understand it, the DI really completes the removal of the unwanted substances. So, I guess I need to find out if the $90 Kent membrane is more cost effective than the $40 Dow Filmtec in terms of DI cartridge replacement costs or do you think it will be a wash.

[rbursek]

PM the DesertRat, I am surprised he has not chimed in here on this one, must be off line today.

[RichConley]

Dow Filmtech membranes are what, 97+% effective? I don't know how effective the Kent membrane is, but, unless its 99.XX%, and you've got really high TDS, you probably won't offset the cost of the membrane in saved DI cartridges.

DI is about $10, and your membrane should be replaced every 2 years or so, so you'd have to go through an extra cartridge every 5 months to offset the cost.


If you have Arizona quality water (1000+ TDS) its worth it to get the best membrane possible. If you have Atlanta water (35 TDS), the difference in DI usage will never offset the cost of the membrane.


You really have to do a cost analysis to figure out if its worth it.

[jjmcat]

My kent membrane lasted allmost 5 years if that helps.

[AZDesertRat]

Kent probably has a slight edge but neither compares to the Select Series individually hand tested and guaranteed 98+% membranes from Spectrapure. Mine averages 99.23% rejection with 800+ TDS tap water.
Spectrapure is the only company that tests each and every membrane for both efficiency and production rates and guarantees them in writing. Dow is an off the shelf and you get what you get, it may be good it may not be. Normally they are in the 96-97% range and you may find one a little better but its a crap shoot. Kents quality has been lacking, they need to stick to supplements and cleaning supplies.

[rbursek]

Thanks for showing up one this one AJ.

[reefinginLA]

Originally posted by jjmcat
My kent membrane lasted allmost 5 years if that helps.

Ughh, that's sickening. Thought I was doing due diligence by replacing mine every year. I guess an investment in a TDS meter is warranted so I don't continue replacing these things unnecessarilly.

[rbursek]

yep

[Thefilterguys]

Filmtec membranes are rated 98% rejection rate off the shelf you can trust their specs. Your water conditions may produce a different rejection rate but it will happen with all membrane with everything being equal. Membranes generally last two to three years under normal conditions and a tds meter would be a big asset to you as its hard to know water quality without one.

Jim