How much of a benefit is there to flushing an RO membrane?

BrettDS · 03/28/2018, 01:44 PM

I recently replaced a cheap RODI unit with a much better BRS unit. The old unit didn’t have a flush valve installed, so I never flushed the membrane in the 2.5 or 3 years that I used it and it still seemed to be doing fine when it was replaced. The new unit has a manual flush valve, but the problem is that my RODI system is automated by my apex. When my ATO reservoir runs low the apex starts the RODI and fills it. When my NSW reservoir runs low the apex starts the RODI and fills it, then emails me to tell me to add salt to it. So I’m not always around or aware of when my RODI system is running to try to flush the membrane. If I notice it running when I walk by I’ll sometimes make a half hearted effort to flush it for 20 or 30 seconds, but that’s kind of few and far between.

I realized today that I have a spare solenoid valve, so with a bit of effort I could connect that to the apex and let the apex automatically flush the membrane. Is it worth the effort to do so? Does flushing the membrane really make a significant difference in the life or efficiency of the membrane? If it matters, my incoming water is softened city water with chloramines at about 300TDS.

If it does make sense to automate a membrane flush how frequently should it do it? Every hour or two that the RODI system runs or once when it finishes a run or just before it starts a run or what? And how long should I allow it to flush each time?

Thanks much

qoeletd · 03/28/2018, 03:16 PM

I use the flush valve for 5-10 minutes after every use to preserve the life of the membrane

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Fraq · 03/28/2018, 03:23 PM

I do this every time i use my RODI unit, the manufacturer recommends it to extend the life of the membrane. I change my membrane yearly and so far have had no issues.

BrettDS · 03/28/2018, 03:28 PM

Quote:

Originally Posted by Fraq

I do this every time i use my RODI unit, the manufacturer recommends it to extend the life of the membrane. I change my membrane yearly and so far have had no issues.

Out of curiosity, why do you change the membrane yearly? I believe they should last several years and you can monitor the TDS coming out of the membrane to see if it’s starting to fail. Why blindly replace the membrane if it’s still performing as well as it did when it was new?

Lsufan · 03/28/2018, 07:56 PM

I flush mine before each use. How much does it actually help,I dont know. It would seem like the DI will last a little longer by doing so. When my unit first comes on the tds is around 80 before the di. After it runs a couple minutes it slowly drops to around 3 or 4 before the di. So I assume not running 80 tds water through the di & letting it come down to 3 or 4 while I’m flushing it helps save the resin.

BrettDS · 03/28/2018, 08:31 PM

Quote:

Originally Posted by Lsufan

I flush mine before each use. How much does it actually help,I dont know. It would seem like the DI will last a little longer by doing so. When my unit first comes on the tds is around 80 before the di. After it runs a couple minutes it slowly drops to around 3 or 4 before the di. So I assume not running 80 tds water through the di & letting it come down to 3 or 4 while I’m flushing it helps save the resin.

I think we might be talking about two different things. TDS creep happens when the membrane sits unused for a while. It’s possible for contaminates to get through the membrane that would normally be rejected. So, as you observed you may see high TDS for the first few minutes when you first start the RO filter. The DI resin will remove any of the extra contaminates, but discarding that water can save your DI resin.

However, what I am talking about is temporarily bypassing the flow restrictor on the waste line to allow a rush of water to move past the membrane and ‘wash it’, for lack of a better term. The unit won’t produce water when the flow restrictor is bypassed, but theoretically doing this regularly can extend the life of the membrane

LQT · 03/28/2018, 08:57 PM

Using a manual flush valve, I flush my membrane for several minutes before and after every use. Not sure if it’s helpful, but I do it every time I make water. However, the more critical thing IMO is using a 3 way valve as a DI bypass to divert the TDS creep water into the drain thereby preserving DI resin life. When I start up my RODI unit, the post membrane RO water reads in the 40s to 50s due to TDS creep from the unit staying idle for a week. It takes 5 minutes or so to get down to 1 for me post RO membrane (100 TDS from the tap).

tletourneau · 03/29/2018, 01:53 PM

I installed an Aquatic Life Smart Buddie Booster Pump, it flushes the membrane every time it's activated. I don't know if it helps but I don't think it can hurt. I am not worried about TDS creep as we use our system for several things besides the aquariums.

BrettDS · 03/29/2018, 08:56 PM

Well, I decided that since I already had the valve it would only take a little work to get it connected, so I went ahead and spent 20 or 30 minutes connecting it and programming it and testing it.

I discovered that BRS sells an auto flush valve and theirs will flush the membrane for 18 seconds of every hour the RODI runs, so I figured that was good enough for me. I programmed the apex to open my valve for 18 seconds every hour whenever my RODI is making water.

I have no idea whether it will make a significant difference in membrane life or efficiency, but for 0 cost (since I had everything I needed laying around) and 30 minutes of my time I figure it’s not going to hurt.

yacn · 03/31/2018, 10:12 AM

I've talked to one of the major manufactures of RO/DI & membrane units. They told me it isn't necessary to flush the membrane but instead it is a money maker for them so they sell it....like others.

Due to that advise I've never flushed the membrane and my TDS meter has always read good quality water coming out

BTW you only need to replace the membrane every 3 + years depending on the quality of water you have....and a TDS meter will tell you when to replace the membrane

I do change the carbon and pre filter every 6 months.

moondoggy4 · 10/25/2021, 08:10 PM

I hope a lot, I flushed mine for 3 years by mistake.

EnderG60 · 10/27/2021, 06:45 AM

I flush mine when my RO output reads 2 TDS or more. When flushing it wont make it go back down I replace it, which is usually about 12-18 months. But i go through about 150 gallons a week.

Keeping up with replacing your carbon prefilter is more important for membrane life.

scrapz · 10/27/2021, 09:45 AM

I replace my membrane every 2-3 years without ever flushing. Is it worth wasting 3 mins of water every time, probably not.

billdogg · 11/14/2021, 07:53 AM

Can't say that I've ever flushed mine either. Replace every couple years or so.

03/28/2018, 01:44 PM	#1
BrettDS Registered Member Join Date: Feb 2012 Location: Orlando Posts: 1,109	How much of a benefit is there to flushing an RO membrane? I recently replaced a cheap RODI unit with a much better BRS unit. The old unit didn’t have a flush valve installed, so I never flushed the membrane in the 2.5 or 3 years that I used it and it still seemed to be doing fine when it was replaced. The new unit has a manual flush valve, but the problem is that my RODI system is automated by my apex. When my ATO reservoir runs low the apex starts the RODI and fills it. When my NSW reservoir runs low the apex starts the RODI and fills it, then emails me to tell me to add salt to it. So I’m not always around or aware of when my RODI system is running to try to flush the membrane. If I notice it running when I walk by I’ll sometimes make a half hearted effort to flush it for 20 or 30 seconds, but that’s kind of few and far between. I realized today that I have a spare solenoid valve, so with a bit of effort I could connect that to the apex and let the apex automatically flush the membrane. Is it worth the effort to do so? Does flushing the membrane really make a significant difference in the life or efficiency of the membrane? If it matters, my incoming water is softened city water with chloramines at about 300TDS. If it does make sense to automate a membrane flush how frequently should it do it? Every hour or two that the RODI system runs or once when it finishes a run or just before it starts a run or what? And how long should I allow it to flush each time? Thanks much

03/28/2018, 08:57 PM	#7
LQT Registered Member Join Date: Feb 2003 Location: Fairfield, CT Posts: 1,516	Using a manual flush valve, I flush my membrane for several minutes before and after every use. Not sure if it’s helpful, but I do it every time I make water. However, the more critical thing IMO is using a 3 way valve as a DI bypass to divert the TDS creep water into the drain thereby preserving DI resin life. When I start up my RODI unit, the post membrane RO water reads in the 40s to 50s due to TDS creep from the unit staying idle for a week. It takes 5 minutes or so to get down to 1 for me post RO membrane (100 TDS from the tap). __________________ - Leon (aka - Water Dog) Deep Blue 57 Edge ATI Acro Garden Build Thread http://www.reefcentral.com/forums/showthread.php?p=25573384#post25573384 Current Tank Info: DeepBlue 57 Edge

11/14/2021, 07:53 AM	#14
billdogg Registered Member Join Date: Apr 2008 Location: Grove City, Ohio Posts: 10,806	Can't say that I've ever flushed mine either. Replace every couple years or so. __________________ I'll try to be nice if you try to be smarter! I can't help that I grow older, but you can't make me grow up! Current Tank Info: 120 mixed reef with 40b sump, RO 150 skimmer, AI Sol Blue x 2, and a 60g Frag Tank with 100g rubbermaid sump. 2 x Kessil A360w lights, BM curve 5 skimmer

03/28/2018, 03:16 PM	#2
qoeletd Registered Member Join Date: May 2016 Posts: 38	I use the flush valve for 5-10 minutes after every use to preserve the life of the membrane Inviato dal mio iPhone utilizzando Tapatalk

03/28/2018, 03:23 PM	#3
Fraq Registered Member Join Date: Mar 2016 Posts: 52	I do this every time i use my RODI unit, the manufacturer recommends it to extend the life of the membrane. I change my membrane yearly and so far have had no issues.

03/28/2018, 07:56 PM	#5
Lsufan Registered Member Join Date: Nov 2013 Location: Baton Rouge Posts: 1,410	I flush mine before each use. How much does it actually help,I dont know. It would seem like the DI will last a little longer by doing so. When my unit first comes on the tds is around 80 before the di. After it runs a couple minutes it slowly drops to around 3 or 4 before the di. So I assume not running 80 tds water through the di & letting it come down to 3 or 4 while I’m flushing it helps save the resin.

03/29/2018, 01:53 PM	#8
tletourneau Registered Member Join Date: Jan 2018 Posts: 46	I installed an Aquatic Life Smart Buddie Booster Pump, it flushes the membrane every time it's activated. I don't know if it helps but I don't think it can hurt. I am not worried about TDS creep as we use our system for several things besides the aquariums.

03/29/2018, 08:56 PM	#9
BrettDS Registered Member Join Date: Feb 2012 Location: Orlando Posts: 1,109	Well, I decided that since I already had the valve it would only take a little work to get it connected, so I went ahead and spent 20 or 30 minutes connecting it and programming it and testing it. I discovered that BRS sells an auto flush valve and theirs will flush the membrane for 18 seconds of every hour the RODI runs, so I figured that was good enough for me. I programmed the apex to open my valve for 18 seconds every hour whenever my RODI is making water. I have no idea whether it will make a significant difference in membrane life or efficiency, but for 0 cost (since I had everything I needed laying around) and 30 minutes of my time I figure it’s not going to hurt.

03/31/2018, 10:12 AM	#10
yacn Registered Member Join Date: Nov 2007 Location: Detroit, Michigan Posts: 212	I've talked to one of the major manufactures of RO/DI & membrane units. They told me it isn't necessary to flush the membrane but instead it is a money maker for them so they sell it....like others. Due to that advise I've never flushed the membrane and my TDS meter has always read good quality water coming out BTW you only need to replace the membrane every 3 + years depending on the quality of water you have....and a TDS meter will tell you when to replace the membrane I do change the carbon and pre filter every 6 months.

10/25/2021, 08:10 PM	#11
moondoggy4 Registered Member Join Date: Jan 2007 Location: menifee So cal Posts: 11,042	I hope a lot, I flushed mine for 3 years by mistake.

10/27/2021, 06:45 AM	#12
EnderG60 Plumbing Engineer Join Date: Feb 2004 Location: Atlanta GA Posts: 3,260	I flush mine when my RO output reads 2 TDS or more. When flushing it wont make it go back down I replace it, which is usually about 12-18 months. But i go through about 150 gallons a week. Keeping up with replacing your carbon prefilter is more important for membrane life.

10/27/2021, 09:45 AM	#13
scrapz Saturation+100 Join Date: Jan 2008 Posts: 3,555	I replace my membrane every 2-3 years without ever flushing. Is it worth wasting 3 mins of water every time, probably not.