RO membrane break in period? High TDS of new membrane

CTaylor · 06/21/2011, 11:44 AM

I just installed dual Filmtec 50 GPD membranes in my RO/DI unit.
The TDS input is about 160. Out of the membranes it is 20-25. Is this because the membranes are new? If so, how many gallons of water is needed to bring down the TDS?
My rejection rate is a little low, at 1:5. Though, would this alter the TDS by that much? I was expecting 5-9 ppm or lower if possible.

Thanks

nanojg · 06/21/2011, 12:06 PM

I have never noticed a break in TDS reading. I get the same TDS 20-25 and my tap tds is normally over 800. Somthing is not right

gldnegle76 · 06/21/2011, 01:49 PM

Your rejection rate is nowhere near 98%, so something is wrong. Did you flush the membranes first? What's your water pressure going into the membranes?

disc1 · 06/21/2011, 03:24 PM

If the membrane is not seated properly then a little bit of feed water leaks over from the high pressure to the low pressure side of the membrane and contaminates the clean water. You can't see the seal on the membrane down in the unit, but it might be worth opening up and give it a little twist / pull / push to make sure it's in there good.

CTaylor · 06/21/2011, 11:00 PM

Thanks for the replies...
I twisted, pushed and pulled on both membranes. The TDS is now 17.
So, it's not normal to filter a few gallons through a fresh RO membrane until the TDS "settles" to a low value?

disc1 · 06/21/2011, 11:29 PM

Absolutely. Those filters aren't perfectly clean when you get them.

CTaylor · 06/22/2011, 04:36 AM

I let it run for the last 6 hours, and the TDS only got to 14. Should it run longer or are the membranes defective?

disc1 · 06/22/2011, 07:50 AM

After 6 hours it should be good. At 14 you are only getting about 90% rejection if your feed water is 160ppm. I would think that something ain't right for sure.

CTaylor · 06/23/2011, 10:59 AM

I asked h2Ofilters (where I got the membranes from) about my situation. He replied as...
I sent off your question to our Filmtec sales rep (our distributor for
Filmtec),

Below is his answer.

The membrane is supposed to have a 98% rejection rate optimal conditions. So
it should be around 4 TDS. When testing myself our water is 260 TDS so I
should have 5-6 TDS but never get lower than 9. When I first install the
membrane it is usually between 14-22 TDS for the first 2-3 weeks and
gradually drops. Other factors such as water temp, pressure, prefilters have
an effect on the rejection rate. Filmtec gets 98% rejection rate on perfect
controlled test conditions. I hope this helps.

gldnegle76 · 06/23/2011, 12:44 PM

Water pressure? What about your sediment and carbon filters, are they old?

CTaylor · 06/23/2011, 03:07 PM

the water pressure is not very high.. 40-45 psi. The carbon blocks about a year old I think. There is 0 ppm chlorine coming out of them.

gldnegle76 · 06/23/2011, 03:45 PM

Yeah, that's low pressure to push through two membranes. Is that pressure coming from tap, or post sediment/carbon blocks?

CTaylor · 06/24/2011, 09:00 AM

it's after the carbon blocks since the guage is on the RO housing

Piper27 · 06/24/2011, 10:28 AM

I am having the exact same problem mine were at 50ppm this mourning with all new filters installed let night. I started a new thread but probably should have joined in here.

gldnegle76 · 06/24/2011, 12:14 PM

Quote:

Originally Posted by CTaylor

it's after the carbon blocks since the guage is on the RO housing

Can you take a pressure reading at the tap and compare the two? It could be time to replace your prefilters, or you may have to invest in a booster pump.

CTaylor · 07/06/2011, 10:11 PM

My pressure dropped to almost nothing soon after my last post. I finally got a replacement second stage (first of two carbon blocks). It was brown, so I knew it was probably clogged. My pressure is now over 50 PSI (at the RO). It may be as high as 60, but my gauge is not accurate. Anyhow, now my PPM output is 5
: )
Thanks for all the feed back.

Buckeye Hydro · 08/07/2011, 04:25 PM

The effect of pressure on rejection is dramatic, especially at the low end of the operating pressure range. Glad everything worked out for you.

Russ

Frop · 01/13/2017, 11:02 PM

I made an account just to reply.

I have a RO/DI, 5 stage, from Melev's Reef.

Tap 800TDS
Softener 670TDS
RO 80-170TDS
DI 0 DTS

That's like 24%! This should be 7% for my crappy membrane.

Quote:

Originally Posted by disc1

If the membrane is not seated properly then a little bit of feed water leaks over from the high pressure to the low pressure side of the membrane and contaminates the clean water. You can't see the seal on the membrane down in the unit, but it might be worth opening up and give it a little twist / pull / push to make sure it's in there good.

I'm going to take a look. Thanks for the advice.

Buckeye Hydro · 01/14/2017, 05:37 AM

Pull the membrane all the way out of the housing.

Inspect to brine seal, and the two orings. Make sure they're not missing, damaged, crimped, creased, etc.

Slide the membrane back in (end with the two small orings first) gently with two fingers. You'll feel it hit the far end. Then put the heel of your hand on the stem and push hard. You'll feel it go in another 1/4". It is that last 1/4" that's critical.

Russ

CTaylor · 01/15/2017, 12:33 AM

wow.. I started this thread for ever ago. I actually think I just solved my problem after all this time..coincdentally after this thread was 'reactivated'! ... the resolution is in my other thread about high chlorine coming out of my carbon(s)

Buckeye Hydro · 01/15/2017, 04:14 AM

I just posted in your other thread. Don't kill the messenger!

Russ

06/21/2011, 11:44 AM	#1
CTaylor Registered Member Join Date: Nov 2001 Posts: 1,524	RO membrane break in period? High TDS of new membrane I just installed dual Filmtec 50 GPD membranes in my RO/DI unit. The TDS input is about 160. Out of the membranes it is 20-25. Is this because the membranes are new? If so, how many gallons of water is needed to bring down the TDS? My rejection rate is a little low, at 1:5. Though, would this alter the TDS by that much? I was expecting 5-9 ppm or lower if possible. Thanks

06/21/2011, 03:24 PM	#4
disc1 -RT * ln(k) Join Date: Sep 2010 Location: Little Rock Posts: 9,705	If the membrane is not seated properly then a little bit of feed water leaks over from the high pressure to the low pressure side of the membrane and contaminates the clean water. You can't see the seal on the membrane down in the unit, but it might be worth opening up and give it a little twist / pull / push to make sure it's in there good. __________________ David Current Tank: Undergoing reconstruction...

06/21/2011, 11:29 PM	#6
disc1 -RT * ln(k) Join Date: Sep 2010 Location: Little Rock Posts: 9,705	Absolutely. Those filters aren't perfectly clean when you get them. __________________ David Current Tank: Undergoing reconstruction...

06/22/2011, 07:50 AM	#8
disc1 -RT * ln(k) Join Date: Sep 2010 Location: Little Rock Posts: 9,705	After 6 hours it should be good. At 14 you are only getting about 90% rejection if your feed water is 160ppm. I would think that something ain't right for sure. __________________ David Current Tank: Undergoing reconstruction...

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
High TDS out of membranes?	beatle	Lighting, Filtration & Other Equipment	9	02/26/2011 05:38 AM
New RO membrane, high TDS, What can be happening?	jjstecchino	Lighting, Filtration & Other Equipment	18	08/23/2010 06:37 PM
High TDS readings after ro membrane change	bioneck47	Lighting, Filtration & Other Equipment	14	06/30/2009 04:02 AM
ro/di break in period	uhuru	Lighting, Filtration & Other Equipment	3	06/02/2007 10:42 PM
RO membrane break in period ?	Blue Deuce	The Reef Chemistry Forum	7	12/08/2006 01:02 PM

06/21/2011, 12:06 PM	#2
nanojg Registered Member Join Date: Jan 2009 Location: Lubbock, Texas Posts: 2,174	I have never noticed a break in TDS reading. I get the same TDS 20-25 and my tap tds is normally over 800. Somthing is not right

06/21/2011, 01:49 PM	#3
gldnegle76 Registered Member Join Date: Jan 2010 Location: Madison, MS Posts: 517	Your rejection rate is nowhere near 98%, so something is wrong. Did you flush the membranes first? What's your water pressure going into the membranes?

06/21/2011, 11:00 PM	#5
CTaylor Registered Member Join Date: Nov 2001 Posts: 1,524	Thanks for the replies... I twisted, pushed and pulled on both membranes. The TDS is now 17. So, it's not normal to filter a few gallons through a fresh RO membrane until the TDS "settles" to a low value?

06/22/2011, 04:36 AM	#7
CTaylor Registered Member Join Date: Nov 2001 Posts: 1,524	I let it run for the last 6 hours, and the TDS only got to 14. Should it run longer or are the membranes defective?

06/23/2011, 10:59 AM	#9
CTaylor Registered Member Join Date: Nov 2001 Posts: 1,524	I asked h2Ofilters (where I got the membranes from) about my situation. He replied as... I sent off your question to our Filmtec sales rep (our distributor for Filmtec), Below is his answer. The membrane is supposed to have a 98% rejection rate optimal conditions. So it should be around 4 TDS. When testing myself our water is 260 TDS so I should have 5-6 TDS but never get lower than 9. When I first install the membrane it is usually between 14-22 TDS for the first 2-3 weeks and gradually drops. Other factors such as water temp, pressure, prefilters have an effect on the rejection rate. Filmtec gets 98% rejection rate on perfect controlled test conditions. I hope this helps.

06/23/2011, 12:44 PM	#10
gldnegle76 Registered Member Join Date: Jan 2010 Location: Madison, MS Posts: 517	Water pressure? What about your sediment and carbon filters, are they old?

06/23/2011, 03:07 PM	#11
CTaylor Registered Member Join Date: Nov 2001 Posts: 1,524	the water pressure is not very high.. 40-45 psi. The carbon blocks about a year old I think. There is 0 ppm chlorine coming out of them.

06/23/2011, 03:45 PM	#12
gldnegle76 Registered Member Join Date: Jan 2010 Location: Madison, MS Posts: 517	Yeah, that's low pressure to push through two membranes. Is that pressure coming from tap, or post sediment/carbon blocks?

06/24/2011, 09:00 AM	#13
CTaylor Registered Member Join Date: Nov 2001 Posts: 1,524	it's after the carbon blocks since the guage is on the RO housing

06/24/2011, 10:28 AM	#14
Piper27 I love bengals Join Date: Feb 2011 Location: Manassas Virginia Posts: 2,512	I am having the exact same problem mine were at 50ppm this mourning with all new filters installed let night. I started a new thread but probably should have joined in here.

07/06/2011, 10:11 PM	#16
CTaylor Registered Member Join Date: Nov 2001 Posts: 1,524	My pressure dropped to almost nothing soon after my last post. I finally got a replacement second stage (first of two carbon blocks). It was brown, so I knew it was probably clogged. My pressure is now over 50 PSI (at the RO). It may be as high as 60, but my gauge is not accurate. Anyhow, now my PPM output is 5 : ) Thanks for all the feed back.

08/07/2011, 04:25 PM	#17
Buckeye Hydro .Registered Member Join Date: Sep 2006 Location: Cincinnati, Ohio Posts: 4,857	The effect of pressure on rejection is dramatic, especially at the low end of the operating pressure range. Glad everything worked out for you. Russ

01/14/2017, 05:37 AM	#19
Buckeye Hydro .Registered Member Join Date: Sep 2006 Location: Cincinnati, Ohio Posts: 4,857	Pull the membrane all the way out of the housing. Inspect to brine seal, and the two orings. Make sure they're not missing, damaged, crimped, creased, etc. Slide the membrane back in (end with the two small orings first) gently with two fingers. You'll feel it hit the far end. Then put the heel of your hand on the stem and push hard. You'll feel it go in another 1/4". It is that last 1/4" that's critical. Russ

01/15/2017, 12:33 AM	#20
CTaylor Registered Member Join Date: Nov 2001 Posts: 1,524	wow.. I started this thread for ever ago. I actually think I just solved my problem after all this time..coincdentally after this thread was 'reactivated'! ... the resolution is in my other thread about high chlorine coming out of my carbon(s)

01/15/2017, 04:14 AM	#21
Buckeye Hydro .Registered Member Join Date: Sep 2006 Location: Cincinnati, Ohio Posts: 4,857	I just posted in your other thread. Don't kill the messenger! Russ