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asylumdown
12-22-2012, 07:16 PM
I noticed on my last water change that my R/O water smells kind of skunky. Not over-powering, but definitely not neutral. It made me check my R/O unit and the TDS was 22ppm. I replaced the DI resin, pre-filter, and carbon 5 weeks ago. Does this mean that my R/O membrane is pooched?

Delphinus
12-22-2012, 07:35 PM
Welllll ... possibly but not necessarily. 22ppm on the output is not great but at the same time it depends on how much it is going into the membrane. If it's say, 50ppm going in and 22ppm coming out, that's kinda lousy but if it's 450ppm going in and 22ppm coming out (in the south I get those kinda #'s but I'm not sure what it is on the north side, our water is out of different watersheds) then it's still doing its job.

FWIW, I replace my prefilters around the 6 to 8 week mark and I get maybe 3 to 4 weeks on the DI. I use colour changing resin but I also measure the TDS coming out and anything above 0 to 1 sustained (a small burst) means it's time to change the DI.

When I run my RO I have to flush the membrane for a good 5 minutes. The TDS surge from having it sit idle in between runs can get as high as 600 to 800. I close the flush valve as soon as it reads <10.

So I guess the question about whether 22 is bad or not kind of depends. Was that a sustained reading or was it part of a surge? If you read again in 5 minutes after running is it still 22?

If it is reading 22 all the time then I would say it is time for a new membrane. Typically, you should get up to about 18-24 months out of a membrane but it also depends on how high the TDS is going in and how often it cycles on and off. It's better to get a good long run less often than many smaller runs producing the same overall volume.

HTH

lastlight
12-22-2012, 07:50 PM
Anything higher than 5 and I replace the membrane. Burns the resin so fast at that point. My incoming seems to be around 200. I flush for a few minutes then run the unit but bypass the resin until the membrane outputs less than 5. Prefilters I replace maybe twice a year. I back flush before and after using the unit. A membrane lasts me about a year but I make very little water now it should last longer.

DiverDude
12-22-2012, 08:15 PM
There have been a number of RO/DI filter questions lately and I'm still gobsmacked that people are throwing out all kinds of figures as to how long between changes of various filter elements but not ONE states how many GALLONS PER WEEK/MONTH they pump through the thing !!

The whole equation boils down to the quality of the water from your tap and how much of it you put through the system per unit of time.

Tony changes out his filters at 6-8 weeks ! I change mine once a year. Tony seems to get his water from a sewer line (800 ppm !!!!); mine's at 100 or less.

I currently have a system volume of about 35Gal and I change 5 gals each week. Tony has a much bigger setup and I don't know what his W/C regimen is.

All that to say, ignore any suggestions on when to change unless they tell you their input TDS, and how much they use it each week !

Personally, I think if the water SMELLS off then I'd dismantle the whole thing and clean it out -AND change out all the filters.

asylumdown
12-22-2012, 08:31 PM
Hmm, all this talk about bypassing stages and flushing... I have a Vertex 100gpd RO/DI unit, it has an automated flush function that comes on for 15 seconds when you turn the unit on, and every 15 minutes of operation, but is it possible for me to manually flush it/bypass the resin?

I don't measure the TDS going in, but I do know that this pre-filter went from white to burnt orange about 3X faster than it normally does. I replaced the RO membrane about 6 months ago, which is why I thought I'd get more out of it, but it really seems to be burning through DI resin now. However, I do 45-50 gallon water changes every single week plus whatever is evaporating from my tank, so I think I probably go through more water than most people.

And in this case, it was a sustained 22pm. I did a water change, which practically drains my RO tank, and in the process I noticed the smell. I checked the unit, (which was already starting to re-fill my RO tank), and it was at 22ppm. I turned it off, and switched out the pre-filter and carbon cartridge (my next set of DI and R/O membranes haven't arrived yet), and turned it back on. For 5 minutes it skyrocketed up to 50ppm, and then very rapidly came back down to 22. By the time I went to bed, it was reading 17ppm, but today it's showing 33ppm.

What's the best way to run the unit? For example, my auto-top off pump is in my R/O storage bin, so as it tops off my tank, the R/O unit is always kicking on to replace the lost water, but it's only ever producing tiny amounts at a time. Is that bad? WOuld it be better to cut the water supply to the RO unit and let the storage tank empty a fair ways before re-filling it? I'm not sure if the way I'm running it is contributing to how quickly it's going through media, or if I'm just using more water than most and have crappy source water.

Delphinus
12-22-2012, 08:51 PM
600-800 is the peak value of TDS surge. Nominal is 200-400. It seems to climb much higher than the input water while it sits there idle. That's why it's really important to flush the membrane otherwise you are replacing the membranes more often which is costly.

mike31154
12-22-2012, 08:57 PM
If you like spending money on replacing DI resin often, then go ahead & plumb your system to your ATO. I think it's been fairly well documented that short runs of an RO system with high input TDS is going to burn through DI media in a hurry since the RO membrane rarely gets a chance to stabilize at a low TDS output.

So yes, disconnect the system from the auto top off & only run it when there's an opportunity to produce at least 10 gallons or more in a single session. Another good idea is to produce at least 5 gallons of RO water only and only after you've done that, start sending the output through your DI stage. You'll need a T-fitting & a shut off valve to divert the RO water before the DI stage. Find something to do with the RO only production water, like making tea or coffee, or beer & bubbly drinking water. This way, the RO TDS has a chance to get to the lowest possible level before feeding the DI stage and your DI media will last longer.

Delphinus
12-22-2012, 08:58 PM
I don't measure the TDS going in, but I do know that this pre-filter went from white to burnt orange about 3X faster than it normally does. I replaced the RO membrane about 6 months ago, which is why I thought I'd get more out of it, but it really seems to be burning through DI resin now. However, I do 45-50 gallon water changes every single week plus whatever is evaporating from my tank, so I think I probably go through more water than most people.


If the prefilter is actually discoloured then it is way past due for a changeout.

The 100gpd membranes on the market have worse rejection rates than good 75gpd membranes. Unfortunately you will burn through DI much faster than proportionally than on a 75gpd.


And in this case, it was a sustained 22pm. I did a water change, which practically drains my RO tank, and in the process I noticed the smell. I checked the unit, (which was already starting to re-fill my RO tank), and it was at 22ppm. I turned it off, and switched out the pre-filter and carbon cartridge (my next set of DI and R/O membranes haven't arrived yet), and turned it back on. For 5 minutes it skyrocketed up to 50ppm, and then very rapidly came back down to 22. By the time I went to bed, it was reading 17ppm, but today it's showing 33ppm.


That definitely sounds like a spent membrane man ... sorry. After about 5-10 minutes of operating mine I will get 0 out of the membrane. I'm using the DI basically to catch the residual TDS in the beginning.


What's the best way to run the unit? For example, my auto-top off pump is in my R/O storage bin, so as it tops off my tank, the R/O unit is always kicking on to replace the lost water, but it's only ever producing tiny amounts at a time. Is that bad?

Ohhhh. Unfortunately yes, you will kill membranes like kleenex that way. I had to learn this the hard way myself after going through 4 membranes in 2 years. One I can accept as bad luck .. two as really bad luck .. when you get to 3 or 4 though then there's a pattern.


WOuld it be better to cut the water supply to the RO unit and let the storage tank empty a fair ways before re-filling it? I'm not sure if the way I'm running it is contributing to how quickly it's going through media, or if I'm just using more water than most and have crappy source water.

Yes - only refill your reservoir once it gets empty and close to empty. That's exactly what happened to me. Ever since changing the way I do things (one long drawn out fill) I've gotten much much better longevity out of my membranes.

mike31154
12-22-2012, 09:01 PM
600-800 is the peak value of TDS surge. Nominal is 200-400. It seems to climb much higher than the input water while it sits there idle. That's why it's really important to flush the membrane otherwise you are replacing the membranes more often which is costly.

Wow! 600-800, that's huge TDS. I thought I read somewhere that anything over 500 is unfit for human consumption and water coming out of your tap is mandated by law to be below that or the supplier has to issue a don't drink or boil before use warning! My tap TDS is around the 210 mark & after flushing my RO system on start up I monitor the TDS for a few seconds after I close the flush valve & the restrictor kicks in. The highest reading I recall observing is in the low 100's, say about 118-120 depending on the time of year. I bypass this water into a waste bucket. It then takes from 3 to 5 minutes for the membrane to get TDS down to 1 or 2. Into a waste bucket it goes until I see a 1 on the TDS meter. After this I start filling an RO container for drinking water, making at least 3 or 4 gallons. Only then do I start sending the RO water through the DI stage. Colder water in winter actually helps the membrane produce a lower TDS sooner.

DiverDude
12-22-2012, 09:14 PM
600-800 is the peak value of TDS surge. Nominal is 200-400. It seems to climb much higher than the input water while it sits there idle. That's why it's really important to flush the membrane otherwise you are replacing the membranes more often which is costly.

Thats odd. I expected that sort of spike at turn on (and in fact, when I disable the DI stage to make RO drinking water, I usually do it before I make tank water to flush the system) but I don't get that. It's 0ppm all the time and when it hits 1 I change prefilter, and carbon (and as it happens, for my current usage, usually the DI is about done as well).

Not sure why I don't get that spike.

DiverDude
12-22-2012, 09:17 PM
Wow! 600-800, that's huge TDS. I thought I read somewhere that anything over 500 is unfit for human consumption and water coming out of your tap is mandated by law to be below that...

It sounds awful, doens't it ? I'm sure the tap water at Tony's place is just fine to drink though. I think if you ask some people who are out of town and are on a well, you'll hear about numbers higher than that.

mike31154
12-22-2012, 09:19 PM
It sounds awful, doens't it ? I'm sure the tap water at Tony's place is just fine to drink though. I think if you ask some people who are out of town and are on a well, you'll hear about numbers higher than that.

Is it possible that he is taking a reading in the wrong place, like somehwere in the waste line? Just can't wrap my mind around that high of a number coming out of a reasonably serviceable RO membrane.

Delphinus
12-22-2012, 09:45 PM
It's the TDS creep, it's legit. It is only that high for a few seconds and it is because the membrane is idle for a period of time. It's not the source water.

Made worse in my case because I double up 2 75gpd membranes to get 150, so I have to read one value that is the sum of both inline.

The TDS creep is why you should flush the membranes. If you don't then they won't last as long as otherwise.

mike31154
12-22-2012, 10:57 PM
Well in that case it makes sense. Had no idea you had two membranes in series.

Reef Pilot
12-22-2012, 11:47 PM
If you like spending money on replacing DI resin often, then go ahead & plumb your system to your ATO. I think it's been fairly well documented that short runs of an RO system with high input TDS is going to burn through DI media in a hurry since the RO membrane rarely gets a chance to stabilize at a low TDS output.

I've heard that, too, but not so sure if that is true. I say that because I run an RO/DI system, and haven't changed out my DI media in over 2 years, and it is still good. Not only do I feed my RO/DI directly to my sump with my own DIY ATO dual float fail/safe system, but I also have 2 pressure storage tanks before the DI (but after the RO) in my system. So I always have about 10g or so of ready RO water, which quickly filters through the DI on demand. We use the RO side for house water in the kitchen too, and those storage tanks always ensure a ready supply for that, too.

My RO membrane is also more than 4 years old, and still working good. I have dual TDS gauges, one after RO (but before DI) and the other measure after RO/DI. However, I have a flush bypass valve (and DI bypass, too), and whenever my TDS from the RO gets over about 2 or 3, I do a flush (about every couple months). After DI, the water tds is still always 0.

scherzo
12-23-2012, 04:59 AM
Our TDS is pretty low compared to Alberta's. If you're like me in Coquitlam. I get about 5-10 TDS right out of the tap.

Our RO membrane will filter most out and I even have zero going into my DI resin at the last stage. This is after 2 years and about 400-500 gallons.

I do flush often and I also change my carbon and per filter every 5 months or so. I still haven't changed my DI.

We're just lucky.


I've heard that, too, but not so sure if that is true. I say that because I run an RO/DI system, and haven't changed out my DI media in over 2 years, and it is still good. Not only do I feed my RO/DI directly to my sump with my own DIY ATO dual float fail/safe system, but I also have 2 pressure storage tanks before the DI (but after the RO) in my system. So I always have about 10g or so of ready RO water, which quickly filters through the DI on demand. We use the RO side for house water in the kitchen too, and those storage tanks always ensure a ready supply for that, too.

My RO membrane is also more than 4 years old, and still working good. I have dual TDS gauges, one after RO (but before DI) and the other measure after RO/DI. However, I have a flush bypass valve (and DI bypass, too), and whenever my TDS from the RO gets over about 2 or 3, I do a flush (about every couple months). After DI, the water tds is still always 0.

mike31154
12-23-2012, 01:53 PM
Yep, most of you folks on the coast could probably forget about the RO membrane & run your water straight through DI after a couple of pre filters + carbon, your tap TDS is so low to begin with. All you might need is something to slow down the flow through your DI so it has time to do its thing. Still have to do the math though, cost of DI & how long it lasts without RO stage etc. This way you would not have any waste water as with the RO plumbed in there.

Reef Pilot
12-23-2012, 02:07 PM
While my tds after DI is always 0, the tds after RO (before DI) will climb to 10 or more if I don't open the bypass valve and flush the membrane. Like I said, I usually do it when I see it climb to a few ppm, and then it is back down to 0 after the flush. Normally, my gauges show 0:0 or 1:0.

The water out of my tap in Langley is about 50 tds normally. However, it must be higher at times (although haven't caught it in a test), because my sediment and carbon filters still need to be changed about every 4 months or so. I can tell when they need changing because my flow slows down, and it takes longer to fill the pressure storage tanks. And I am always amazed at the red/brown sediment in the pre-filters, despite the seemingly clear tap water.

I still don't think fast flow through the DI is a problem though, as I have that with my RO pressure storage tanks. I do agree though, you should have an RO membrane.

mike31154
12-23-2012, 02:44 PM
With TDS 50 at source, DI only would probably not be economical. I've heard some of you on the west coast have TDS 10 or lower though, so it might be an option for those lucky few.

Reef Pilot
12-23-2012, 03:26 PM
With TDS 50 at source, DI only would probably not be economical. I've heard some of you on the west coast have TDS 10 or lower though, so it might be an option for those lucky few.
Just checked my tap water and it is 64 at the moment. Have never seen it at 10 in Langley. I understand they also supplement here with well water (not sure why as we are tied in with the Metro Vancouver water supply).

Back to the OP question, here is some info on DI replacement from the manufacturer of my RO/DI unit.
http://www.airwaterice.com/category/z.2/

I have this unit, but with the 75 gpd membrane. I bought it used and still going strong.
http://www.airwaterice.com/product/1EXTREMETYPHOONIII/EXTREME-TYPHOON-III-150-GPD-RODI-with-Gauge-TDS-Alarm-Dual-TDS-Meter.html

Rogue951
12-23-2012, 03:47 PM
I'm in east van and I average 16ppm. My membranes usually last a few years, usually I change it out of age rather than use. Same with the prefilters. easily 6 months between changes.
except this summer a few houses in my area were torn down rebuilt with water main work and I've noticed the sediment filter change color so I've swapped them out faster. Water also smelled a little different but nothing alarming.
Maybe you had construction in your area to cause a spike in impurities?

We're really lucky out here never realized it till I saw the value's of other places.

gregzz4
12-23-2012, 09:47 PM
Adam, besides your membrane possibly needing replacement, it's possible you need to sterilize your system due to bacteria
If this is the case, you'll need to replace all your filter media

Buckeye Field Supply suggests this method;

We recommend sanitizing your RO/DI system approximately once per year. Schedule this process at a time when you are planning to replace your cartridges. These instructions apply to water purification systems without a pressure tank. Before you begin assure that you have about an hour available, and that your work area and hands are clean.

Turn off the water supply to the system.

Remove all housings and remove all pre-filters and post-filters from the system including sediment filters, carbon filters, in-line filters, and deionization cartridges. Remove the reverse osmosis membrane(s).

Wash housings with a soft brush or cloth in warm soapy water. Rinse thoroughly to remove all soap. Don't forget to carefully remove and wash all o-rings. Lubricate the o-rings with a small amount of silicone grease and reinstall them.

Fill each vertical housing with one cup of potable water and three to four tablespoons of household bleach, and with this sanitizing liquid still in the housings, screw them back on to the system.

Turn on the water supply a bit, allow water to fill the entire system, and assure water is flowing out of the waste line and the purified water line. Place the outlet of the drain tube and purified water tube slightly higher than the system to assure these tubes are full of the sanitizing solution. When the sanitizing solution has reached the outlet of each tube, and with the outlet of each tube placed above the rest of the system, shut off the water supply for 30 minutes.

After 30 minutes, turn the water supply on and assure that water exits the system from both the drain tube and the purified water port. Flush the sanitizing solution from the system for 5 to 10 minutes.

Turn off the water supply and install new filters, taking care to flush the filters as appropriate.

We recommend keeping a maintenance record for your system. Record the date of the sanitizing and filter replacement.