RO/DI new membrane problems

vasinvictor · Mar 18, 2013

After 2 1/2 years my membrane needs to be changed. However the new Dow membrane is off some how. When I put the membrane in, it blocks the clean water line somehow and all I get is waste water. I ran it for about 2-3 hours and not even a single drop of clean water. The water pressure is fine as the old filter worked fine. Attempting to see if some thing clogged the line, I put on the old filter and almost clean water started flowing again. I thought most of these filters where universal and easily swapped out. Some input would be great and thank you in advance.

AZDesertRat · Mar 18, 2013

What brand and model of RO system do you have and what model of membrane did you buy as a replacement?
Did you install a new matched flow restrictor to go with the new membrane?

Dow Filmtec makes a couple different models of membrane and not all are the same. The most common is the 1812 series but they also have a 1810 series that is not compatible and is used in many Whirlpool, Sears and Watts Premier systems to name a few.

AlexAquaFX · Mar 18, 2013

Yea flow retrictor was the first thing that came to mind. If its missing or not functioning correctly it can let all your pressure fly down your waste line, not leaving enough to permeate your membrane. The fact that you mention putting in the old membrane and it working though somewhat indicates otherwise. For one to work and the other to not really makes me lean towards a incompatible or bad membrane. Let us know some more information and we should be able to figure it out! Goodluck

vasinvictor · Mar 18, 2013

The ro system is a 6 stage Pure water club system purchased off of ebay. PureWaterClub.com with a 450 flow restrictor
The new membrane is a Dow TW30-1812-75 I attempted to use the original flow restrictor 450 and also with a 600 restrictor.

vasinvictor · Mar 18, 2013

I believe the 600 restrictor is the proper size.

vasinvictor · Mar 19, 2013

Has anyone had a similar problem?

AZDesertRat · Mar 19, 2013

Pick the system up in your hands while it is hooked up and rotate it all around in different directions to see if it has any trapped air inside the membrane housing causing an air lock or binding. Temporarily kink the end of the waste line to see if it starts flowing treated water. What is the water pressure at the RO membrane? What is your water temperature?
Measure the waste flow and tell us how many ounces or m/L it produces in exactly one minute.

vasinvictor · Mar 19, 2013

I kinked the end, and there was enough pressure to move a water drop in the tube about 3 cm. then stopped, the temp is @ 54 degrees, I'm not sure on pressure but the old membrane worked well. The waste line produced a little over half a gallon in 1 min. with the new membrane and zero clean water. I did however notice on the old membrane that worked the end with the double black rings was shorter than the new dow membrane , by a little. They where both 1812's but the only difference was the gallons per day. As the old unit was 100 and new 75.

AZDesertRat · Mar 19, 2013

How much shorter? The 1810 series looks similar but is a different animal. Are the number, size and placement of the seals and O-rings identical between the two?

The 1/2 gallon of waste in one minute is puzzling, you should only see around 24 oz at most with a 75 GPD membrane under ideal conditions.

AlexAquaFX · Mar 19, 2013

Honestly sounds like a bad membrane.. I have not seen one personally that was fresh and locked up like that, but I have heard of it. Have you contacted the company that sells the unit, or that you purchased the replacement membrane from?

vasinvictor · Mar 20, 2013

No, I haven't contacted anyone Alex. Az the double rings look the same in size, placement and distance from eachother. However the end with the o- rings are just a little longer on the filter that doesn't work. The filter has been stored in my garage this whole time but it never drops below freezing in there. Could the temp getting close to freezing have this kind of effect on a membrane? I am puzzled! I'm just going to buy a new one ...any good recomendations?

mcarroll · Mar 20, 2013

I've seen similar results with an improperly installed membrane....IIRC it was not inserted all the way into the canister. I think in that case that may have diverted all the flow to the product line vs the waste line as in your case however. Regardless, double check that your membrane is seating into the housing properly and fully - compare with your old membrane if you still have it. It sometimes takes what feels like "too much force" to get it in all the way.

Any chance the flow restrictor is on the wrong line? (Should be on waste.)

I think odds are it's something dead-simple....one of the above or something else related to installation, or as others suggested already just a bad membrane. (Never heard of a bad membrane, and having a "total failure" in what amounts to a rolled up sheet of perforated rubber seems unlikely, but anything is possible.)

If you haven't already, I would also let the seller know what's going on....don't wait on that IMO.

Hope this helps!

-Matt

P.S. A DOW membrane from Spectrapure or any of the other vendors should perform equally well. Just make sure to dial in a 4:1 waste to product ratio on whatever you end up with...and expect to pay about $40 or so.

AlexAquaFX · Mar 20, 2013

Yea unfortunately I never got my hands on the "Locked" membrane, so I could not test it myself to see if it was just some sort of human error preventing it from functioning properly. I'd be interested in checking yours out. If you don't get it to work and decide to throw it out, please let me know. As far as a replacement membrane like Mcarroll said make sure you get one that uses DOW sheets, I recommend one that has been wet tested and meets its published specs.

AZDesertRat · Mar 20, 2013

I recommend the MEM-S-0090 90 GPD high rejection rate SpectraSelect membrane and matched capillary tube flow restrictor from Spectrapure. It has been specially treated to improve its performance and is then individually hand tested and guaranteed in writing to be better than 98% rejection. My personal Select membranbe is over 5 years old and still running at 99.4% rejection rate. The reason the rejection rate is so important is for every 2% you lose you cut your DI life in half so a 90 or 96% rejection rate will cost you much more in DI replacements over the life of the membrane.
$45 about half way down the sales flyer here:
SpectraPure - Great Deals on All your Water Management needs!

and the capillary tube flow restrictor is here:
RO MEMBRANES AND FLOW RESTRICTORS

All Spectrapure RO membranes are specially treated and either batch tested with the $35 ones or individually tested and guaranteed better than 98% with the $45 ones.

Whasmack · Mar 15, 2023

I believe I also got a bad membrane - I recently got the 75 GPD Dow membrane from BRS, and swapped out the sediment, carbon, RO and flow restrictor at the same time. (Sadly I threw them away).
In 2 days, I've only been able to make about 50 gallons of good water with it running continuously. Source water temp is around 50's, but that's never been an issue before. 64 PSI at the membrane.
I also measured the waste water & timed it - about 130mL in 15 seconds, so that checks out for a 550mL restrictor.

I also realized my TDS meter isn't reading correctly at that time