RO/DI Question

[Reefing Newbie]

I have a BRS RO/DI unit that I bought second hand a month or so ago. I replaced the first three filters(5 micron Carbon, .6 micron carbon, and the Purtex Sediment filter, 5 micron I think). The DI resin was pretty much used up so I went to my lfs on black friday to pick up the resin they had on sale(BRS color changing, I assume because BRS is located about 15 miles away). Replaced that about 2 weeks ago and now the bottom fourth of the resin is brown already. Is this normal or is there something wrong? My lfs told me that is should last me about a year, so I don't think two weeks should have that much of an impact on it. The RO membrane for the unit is only 7 months old and just yesterday we added the water saving kit so that is a second membrane. My TDS runs between 235-260, which I think is about average right? Any suggestions on what to do? Every filter is no more than a month old... I use the flush kit before every use to keep the extremely high TDS water from entering the DI chamber.

[Reefmedic79]

How many chambers do you have? From the above description it sounds like there are 6: 2 RO, 1 DI, and 3 particulate filters.

If the first RO membrane is 8 months old it probably needs to be changed. How often the filters need changing is determined by your source water more than the age.

What is the TDS of the source water?

Your end product out of the filter should be as close 0 as possible, but under 20 or so should be usable.

[greg0385]

Are you on well water? High co2 will destroy your di resin life. Whats your tds after the membrane? Whats your water pressure? All of those above will factor in on resin life

[Reefing Newbie]

Yes 6 stages, just like you said.

The first RO membrane being fed is the new one from the water saving kit(which was just put on yesterday). The second RO membrane(the one that we got with the unit) is being supplied by the first membrane's waste water like the BRS video said to do. The previous owner of the unit never changed the particulate filters and kept changing the DI, would this add to a fast decline in the RO membrane's usable live?

The TDS of the water souce is usually 245-250. Good days are as low as 234(when my mom does laundry) and the bad days are 260.

The end product is 0, I have the dual in line TDS meter.

[greg0385]

Your prefilters protect your membrane from clogging and not working correctly as well as trapping out harmful particles(copper and such) prefilters should be changed every 6-12 months or pending how much water you make.

[Reefing Newbie]

Are you on well water? High co2 will destroy your di resin life. Whats your tds after the membrane? Whats your water pressure? All of those above will factor in on resin life

My water is from the city, not well water. I have no idea what the co2 levels are in our water. TDS after both membranes reads zero, so that means that the DI resin should last quite awhile right? The water pressure is at 62, was at 65 before the addition of the second membrane, is this fine or should I be adding a booster pump?

[Bens_Reef]

i would check the tds after the older RO membrane but before the next filterand see what you are getting, if youre tds here is less than 10% of your pre-filtered TDS then your ro membrane is ok, generally your DI resin only does the last 2-5% of your TDS, the more that gets through RO the faster your DI goes bad.

for instance my tap is around 250 TDS (good for well water) around 25 after my RO(not too bad) and 15 after my DI (yeah i know, i need a new one)

[Bens_Reef]

i think 60 PSI is around the top end for a non-commercial system, you might blow seals with more pressure

[Reefing Newbie]

The water I tested before the DI is fed from both membranes. The two good water out puts come together at a Y. I tested after the Y. Should I test the waste water from the first membrane, because that is what is feeding the older one? The TDS after the Y(good water) is reading 0, so I would like to know what is up with this.

[Bens_Reef]

so what you are saying is the waste water that normally goes down the drain is being recycled so to speak and going into your pure water holding tank? does the effectivly double your GPD?

well thats really good, with 0 tds you really arent even using the DI as for it turning color already....... if its pure going in then there shouldnt be anything to change the color with

[greg0385]

As said above you want to know the tds before it goes into your resin. It was said on another post that for example if your ro water is 1tds vs 100tds. Than your di resin should last 100times longer because its got to work lots less. ( i may have worded that wrong but i hope you get the point) 60psi is great and you should be fine on co2 as your water is treated at a water plant.

My tds is 22 in and 4 after the membrane but i have high co2 because of well water so i have airate the ro water befor it goes into the resin. Otherwise i only make about 90 gallons of good water before the resin is exhausted.

[Reefing Newbie]

Here are pictures of how it is set up:
http://i1182.photobucket.com/albums/x450/kriben1/0c15b6a3.jpg

The water starts at the first chamber of the RO unit(DI is the far right chamber), the red line feeds it. After the 3 particulate filters it goes through the red line in front(connected to auto shut off) to the top RO membrane(purchased and installed yesterday. The waste water from that one feeds the second bottom RO membrane. The good water goes through the blue line to the Y. The waste water from the second membrane(black line) goes to the drain. The good water(blue line) goes to the Y like the other. From the Y they go to the auto shut off valve then to the DI chamber. After that it goes into buckets(when I am running it). I tested after the Y and got 0 TDS readings.

Close up of RO membranes(top new, bottom 7 months old). Waste water from the top is fed to bottom one via the white line.
http://i1182.photobucket.com/albums/x450/kriben1/f22deb7c.jpg

DI chamber showing the color change.
http://i1182.photobucket.com/albums/x450/kriben1/2cd56e79.jpg

[Bens_Reef]

My tds is 22 in and 4 after the membrane but i have high co2 because of well water so i have airate the ro water befor it goes into the resin. Otherwise i only make about 90 gallons of good water before the resin is exhausted.

how do you airate it first because i think i have this problkem as my DI is only about 3 months old and ive made probably 300 gallons with it and im at 15 TDS today after DI

[Reefing Newbie]

so what you are saying is the waste water that normally goes down the drain is being recycled so to speak and going into your pure water holding tank? does the effectivly double your GPD?

well thats really good, with 0 tds you really arent even using the DI as for it turning color already....... if its pure going in then there shouldnt be anything to change the color with

The normal waste water from the first membrane is run through the second membrane increasing the unit from 75 GPD to 150 GPD. It should cut waste water from 4 gallons of waste to 1 gallon of 0 TDS down to 2.5 gallons of waste to 1 gallon 0 TDS. I am trying to figure out why the resin is turning already being that I know the water going into it is pure. Today my inlet to the whole unit is running at 244 TDS(before filter) and comes out 0 before DI and after DI.

[Bens_Reef]

i would look into the Co2 then, so far thats the only thing anyone has posted here that would explain your dilemma. i too would be interested to know how to solve this. gonna tag along for the ride

[Reefing Newbie]

Would I need to call the city to ask about co2 levels? The resin has gotten more brown since I turned it on. It was about 1/4 the way up before use and is about 1/3 maybe a little more.

[greg0385]

After your ro membrane, run a line over to a bucket/container. Have a airstone or a bubble wand to airate the water. Then have a small pump of some sort pump it into your di chamber. Allow it to airate for a bit before pumping into the di chamber and you should be good.

[Bens_Reef]

since the DI chamber doesnt slow down flow like the RO membrane does, you could make up a 55G drum of RO water, airate it overnight at minimum and then right before it goes to the mixing tank it could be run through the DI part for 100% pure and less Co2, there are some small pumps that ive bought for use in a dart frog tank that would be perfect for this i think.

[Reefing Newbie]

How would I figure out if the co2 is causing the problem? I don't really want to do something to solve a problem it might be, I want to figure out the problem first then go from there.

[greg0385]

I think there is a test you can do or maybe call the water department. Im sure someone can help you out more how to test for co2

[Bens_Reef]

you can probably take a sample to a place that deals with water filtering systems or maybe the water department as Greg said, other than that you can call a company that does well inspections, i know they do some kind of water tests, i had to pay for one on my well when i bought my house and they tested the water for stuff

[Reefing Newbie]

Okay, I will try to do that tomorrow. I may or may not though, kind of busy tomorrow.

[Buckeye Hydro]

Just saw this thread now. Lots of things in the tread I want to comment on so here goes:

I replaced the first three filters(5 micron Carbon, .6 micron carbon, and the Purtex Sediment filter, 5 micron I think

Hmm. With this filter combo you are asking your 0.6 mic carbon block to act as a sediment filter. A better combination, in order of water flow, would be:
1 mic sed filter
0.6 mic carbon
5 mic carbon

Additionally, unless you have chloramines in your water, no need for 2 carbon blocks.

In regard to running a second membrane in series like you have:
First - remember that what folks call "waste water" really would be better thought of as "flush water" in that this water serves the important purpose of internally flushing the surface of the semipermeable membrane to keep the membrane from fouling/scaling.

When you configure a system with two membranes in series (the waste from the first membrane going to the "in" port on the second membrane), for this discussion let's say it's two 75 gpd membranes, the system behaves like you have a single long (75 gpd x 2) 150 gpd membrane.

Now - if you use a proper flow restrictor, that is, one for a 150 gpd membrane, you'll have about a 4:1 waste to product ratio. Sounds familiar, right?

If however you don't change the flow restrictor - meaning you keep using the same restrictor you were using when you just had one 75 gpd membrane, then you'll see a waste to product ratio much lower than 4:1. But remember that the recommendation for a ~4:1 ratio comes from the membrane manufacturer. They are telling you that you need about a 4:1 ratio to keep the membrane flushed and keep the membrane from fouling or building up scale. Run the system with a lower ratio and you will foul/scale the membrane(s) quicker than would have otherwise been the case.

Instead of adding a second membrane to lower that ratio, you could have just changed out your flow restrictor ($4) instead. A much less expensive approach to get you to the same endpoint in terms of saving on waste water.

Now, to confuse things just a bit. Filmtec specs call for the 4 to 1 ratio on the basis of assumptions about the water that will be supplied to the membrane. If you have very soft water you MAY be able to get a decent service life from the membrane running at a ratio lower than 4 to 1 (e.g., 3 to 1). Remember that the waste water from the first membrane is about 25% harder than your tap water.

Bottom line: If what you are after is reduced waste water, experiment with a different flow restrictor for $4 instead of messing around with a second membrane plumbed in series.

As a side note, you can also lower the ratio by increasing the pressure delivered to the membrane (with a booster pump), because flow restrictors are sized assuming you are providing factory spec conditions (50 psi and 77 degrees for Filmtec membranes). Increase the pressure and you'll drive more water through the membrane and viola - less waste water. But as I mentioned above, if you do this (just like over-restricting a membrane) - the lower the waste to product ratio, the shorter the lifespan on the membrane.

Makes sense?

Russ

[Buckeye Hydro]

How many chambers do you have? From the above description it sounds like there are 6: 2 RO, 1 DI, and 3 particulate filters.

"Particulate filter" is another name for a "sediment filter", and you only have 1 sedimdnt filter. You have 3 "prefilters." A "prefilter" is any filter that treats the water before it reaches the RO membrane.



If the first RO membrane is 8 months old it probably needs to be changed.
Typically you should expect 2 to 5 years of useful life from your RO membrane.

Your end product out of the filter should be as close 0 as possible, but under 20 or so should be usable.
We'll save this discussion for another thread, but I would be careful with this piece of advice.

[Buckeye Hydro]

My water is from the city, not well water. I have no idea what the co2 levels are in our water. TDS after both membranes reads zero, so that means that the DI resin should last quite awhile right? The water pressure is at 62, was at 65 before the addition of the second membrane, is this fine or should I be adding a booster pump?

It is very unlikely that your RO water is 0 ppm. Really not possible. Something is wrong with that reading,

Russ

[Buckeye Hydro]

i think 60 PSI is around the top end for a non-commercial system, you might blow seals with more pressure

60 psi is OK. The membranes you're using are probably Filmtec membranes and are spec'ed at 50 psi. The membranes can handle about 300 psi, but other components in your system can't. Plumbing code says keep it at 80 or below. No danger of blowing out any seals at 60 or 65 psi.

[Reefing Newbie]

I think that makes sense... I may need to read it over a few more times, but I got the just of it. We already bought the second membrane, not knowing new restrictors could have the same effect. I didn't place the particulate filters in order, I was just listing them off. The order we were told to put them in by the lfs was; 5 micron sediment, 5 micron cabon block, then .6 micron carbon block. So you say I should switch the two carbon blocks around? I will ask about chloramines in my water when I ask about co2. If I don't have them what would you recommend?

Now I have a couple questions that just arised, especially now that I have a manufacturer looking into this.

- Could I still mess with flow restrictors or booster pumps with my system having two membranes on it? Would this make it even more efficient or just be a waste of time?
- Should the DI chamber be full of water when not being used? Or free of water? I just thought about this now after my dad mentioned it.
- Doesn't the whole flush kit do the flushing for the system? With flushing for a few minutes before using, does it still need the 4:1 or 3:1 ratio?
- If the membrane needs the flush ratio at 4:1, how exactly do you cut down on unusable reef water?

[Buckeye Hydro]

Would I need to call the city to ask about co2 levels? The resin has gotten more brown since I turned it on. It was about 1/4 the way up before use and is about 1/3 maybe a little more.

Unlikey you have a co2 issue.

Please tell us the pH and alkalinity of your RO water. From that I can tell you your CO2.

Russ

[Reefing Newbie]

It is very unlikely that your RO water is 0 ppm. Really not possible. Something is wrong with that reading,

Russ

I should probably get a new inline TDS meter then.

[Buckeye Hydro]

We already bought the second membrane, not knowing new restrictors could have the same effect. I didn't place the particulate filters in order, I was just listing them off. The order we were told to put them in by the lfs was; 5 micron sediment, 5 micron cabon block, then .6 micron carbon block. So you say I should switch the two carbon blocks around?

If you don't have chloramines you don't need two blocks. But if you are going to use those two, given the two drastically different chlorine capacities of those two filters, yes - put a 1 mic sed followed by the 0.6 block and then the 5 mic block.



I will ask about chloramines in my water when I ask about co2. If you tell me the name of your water utility, town, county, and state, I'll check that for you now.



If I don't have them what would you recommend? Use the two carbon blocks you have, but next filter change don't buy another 5 mic carbon.


Could I still mess with flow restrictors or booster pumps with my system having two membranes on it? Would this make it even more efficient or just be a waste of time?
You should use a flow restrictor that yield a 4:1 ratio of waste water to purified water.

Higher pressure is always better, but I don't think you have a screaming need for a booster pump.




Should the DI chamber be full of water when not being used? Or free of water? I just thought about this now after my dad mentioned it.

Not critical - you just have some air trapped in the housing.



Doesn't the whole flush kit do the flushing for the system? With flushing for a few minutes before using, does it still need the 4:1 or 3:1 ratio?
Yes

f the membrane needs the flush ratio at 4:1, how exactly do you cut down on unusable reef water?
You want a 4:1 ratio to give you a reasonable membrane life. If you use softened water you could skinny that up to a 3:1. If you are ok with a shorter life on your membranes, something less than a 4:1 is ok.

[Buckeye Hydro]

I should probably get a new inline TDS meter then.

Are the batteries ok?

Are the probes aligned correctly (check you instructions)?

[Bens_Reef]

60 psi is OK. The membranes you're using are probably Filmtec membranes and are spec'ed at 50 psi. The membranes can handle about 300 psi, but other components in your system can't. Plumbing code says keep it at 80 or below. No danger of blowing out any seals at 60 or 65 psi.

thank you very much for your knowledge from this post and the others in this thread, and i would be interested in the formula for the Co2 as i think i may have an issue with this as well.

[Reefing Newbie]

I bought this unit, everything but additoinal membrane included, second hand. Should I recalibrate it?

[Reefing Newbie]

Okay, re-worked the meter and I am getting a reading of 4 ppm TDS. Is this more accurate than the reading of 0 I had before? Could you explain the reasoning behind putting the .6 micron carbon block before the 5 micron carbon block? I told my dad that they should be switched and he doesn't think they do.

[Buckeye Hydro]

Okay, re-worked the meter and I am getting a reading of 4 ppm TDS. Is this more accurate than the reading of 0 I had before?

We don't know which is more accurate because we are not comparing either reading to a known quantity. Suggest you borrow a meter you know is accurate and compare that to what you're reading. Also - temporarily switch the probes and see what you get.

Could you explain the reasoning behind putting the .6 micron carbon block before the 5 micron carbon block? I told my dad that they should be switched and he doesn't think they do.

Sure.

First, let's talk about prefilter pore sizes. Understand that people intuitively want to have the pore size in each successive filter smaller than the last. For instance, a 10 mic sediment followed by a 5 mic carbon followed by a 0.5 mic carbon. This idea is OK, but SHOULD BE APPLIED TO SEDIMENT FILTERS ONLY. Otherwise you are asking the carbon blocks to act as sediment filters. They'll do that, but you want the carbon blocks clean and fully available to do their job - remove VOC's including chlorine. Use much less expensive sediment filters designed for the purpose to remove sediment. The pore size on your carbon block(s) should be about the same size as, or larger than the smallest pore size on your sediment filter(s). So let's say you had wonderful water pressure, were using multiple sediment filters to deal with heavy sediment loads, and two carbon blocks to deal with chloramines. This would be a good configuration:
10 mic sed->5 mic sed->1 mic sed->0.5 mic carbon->5 mic carbon

This would be a bad configuration:
10 mic sed->5 mic sed->0.5 mic carbon

Next, remember that carbon blocks are also rated on their chlorine capacity - meaning how many gallons of chlorinated water can they treat. Our 0.5 mic blocks have a 20,000 gallon capacity, and our 5 mic blocks have a 6,000 gallon capacity.

Also be aware that the first carbon block will remove nearly all the chlorine (or treat nearly all the chloramine), and the second block is there to catch any that gets through.

Also remember that we ARE NOT using these blocks as sediment filters (see above). So if you configure your system with the 6,000 gal block ahead of the 20,000 gallon block, the 5 mic block will be exhausted long before the 0.5 mic block, and you'll be left with only the 0.5 mic block treating the chlorine/chloramine. If you put the better block (0.5 mic) first, it will do nearly all of the work, but may pass small amounts of chlorine/chloramine onto a fresh 5 mic block. So you team up the tough job (initial VOC treatment) with the better 20,000 gallon block, and leave the lesser quality block to treat any little bit that gets through.

This makes sense once you rid yourself of the notion that each successive filter should have smaller pores.

Russ

[Reefing Newbie]

What would be a good configuration for two sediment filters and one carbon block? You say in the example above with the two sediment filters and one carbon blocks it is bad. Thanks for all the help!

[Buckeye Hydro]

Its not that two sediment filters is bad, its that the pore size on the carbon block is 5 mic smaller than the smallest pore size on the sediment filter.

For example,
10 mic sed->5 mic sed->5 mic carbon block is a good combo
5 mic sed->1 mic sed->0.5 mic carbon block is a better combo

[Reefing Newbie]

Okay thanks! That really helps a lot, now I know a lot of useful info on RO/DI units that I didn't know before.