Need help with what RO unit to buy.

[CherBear811]

My city's tds are 575 with 1 ppm Nitrate, and Chlorine .2-.6. My chlorine tests results are usually very low, .25 range. The city does not say they use chloramine.

So... obviously I am going to need more than one DI chamber for the high tds.

But I am also wondering what stages I should get for pre-membrane to preserve the life of the membrane since I nearly have rocks coming out of the tap.

On the big BRS unit, they have 2 carbon blocks rather than an extra sediment, but with 1 ppm nitrate and low chlorine and no chloramine, I don't think I need 2 carbon blocks. I am wondering if I should run a 5 micron sediment 1st, then a 1 micron sediment, then the carbon, and then membrane? Or should I just run the basic 1 sediment, 1 carbon, membrane, then 2-3 DI chambers?

 

[Idoc]

I'd start out with the smallest unit and add additional canisters if needed once you test the out-water source.

 

[Crabs McJones]

I think I would still do one sediment and two carbon blocks. Sediment filters trap just that, sediment and suspended solids. Trace pathogen elements, heavy metals, and volatile organic compounds can still remain in your water. Carbon blocks do alot more by removing chlorine, volatile organic compounds, odors and unpleasant tastes from water.
So i'd do sediment, dual carbon block, RO membrane, and DI cartridge.

 

[chipmunkofdoom2]

There's not really a benefit to running two sediment filters. To understand why, you need to understand why we use sediment filters in the first place.

The sediment filters protect the system from particulate matter in the water supply. Technically, since large particulate matter would also clog your carbon blocks, really the sediment filter is all about protecting your carbon blocks. This is worth doing, because if carbon blocks plug with sediment before they lose their ability to remove chlorine/chloraime (their primary function), some of their useful life has been wasted.

There isn't any benefit to running two sediment filters because all the first would do would is protect the second. It's much easier to just run a single sediment filter with a very small pore rating (0.5 microns if you can find it). Then, when your pressure gauges tell you the pressure is dropping, just replace the single sediment filter.

I personally always choose to run two carbon blocks. The reason is because chlorine/chloramine is particularly damaging to RO membranes. RO membranes can last years (my last one lived for over 10 years), so protecting the RO membrane well is worth doing.

It's also not accurate to say that you'll need more than 1 DI stage because you have high TDS. Your membrane will remove between 96 and 99% of TDS. There are legitimate reasons to running multiple DI stages, and I'm a really big fan of running multiple stages. I'm upgrading my unit and adding a fourth DI stage today, making my unit 8 stages total. But high source TDS alone is not a good reason to have multiple DI stages. If you have high source TDS, it's better to ensure you have adequate pressure (50 PSI or more) and that you have a proper waste to product ratio, which is 4 to 1.

 

[CherBear811]

There's not really a benefit to running two sediment filters. To understand why, you need to understand why we use sediment filters in the first place.

The sediment filters protect the system from particulate matter in the water supply. Technically, since large particulate matter would also clog your carbon blocks, really the sediment filter is all about protecting your carbon blocks. This is worth doing, because if carbon blocks plug with sediment before they lose their ability to remove chlorine/chloraime (their primary function), some of their useful life has been wasted.

There isn't any benefit to running two sediment filters because all the first would do would is protect the second. It's much easier to just run a single sediment filter with a very small pore rating (0.5 microns if you can find it). Then, when your pressure gauges tell you the pressure is dropping, just replace the single sediment filter.

I personally always choose to run two carbon blocks. The reason is because chlorine/chloramine is particularly damaging to RO membranes. RO membranes can last years (my last one lived for over 10 years), so protecting the RO membrane well is worth doing.

It's also not accurate to say that you'll need more than 1 DI stage because you have high TDS. Your membrane will remove between 96 and 99% of TDS. There are legitimate reasons to running multiple DI stages, and I'm a really big fan of running multiple stages. I'm upgrading my unit and adding a fourth DI stage today, making my unit 8 stages total. But high source TDS alone is not a good reason to have multiple DI stages. If you have high source TDS, it's better to ensure you have adequate pressure (50 PSI or more) and that you have a proper waste to product ratio, which is 4 to 1.

First, thank you for taking the time to write that out. Your time spent is much appreciated!

Second, this all makes a lot of sense. The units I am looking at all come with 5 micron sediment and carbon blocks. I was going to replace with 1 micron once they clogged up, but after what you said about protecting the membrane (and they are definitely more expensive to replace) I am wondering if I should order 1 micron cartridges from the start, at least for the sediment?

Also with regard to carbon, I am looking at a unit that comes with a coconut carbon block (my understanding is this is to remove VOCs?) and a GAC. Is that also recommended?

Third. For the DI, for now, until I see what exhausts faster, I am thinking of running one cartridge half anion packed in first and the second half half cation, then a second mixed bed cartridge as the last stage. For space reasons I'd really like to avoid 3 DI chambers. Once I know whether the anion or cation exhausts faster, I would probably repack accordingly (ex: if anion exhausts noticeably faster, I would pack 2/3 anion and 1/3 cation, and leave the last stage still a mixed bed.

 

[chipmunkofdoom2]

Glad to help

The 5 micron sediment filters and carbon blocks are probably okay. I always prefer to run a smaller sediment filter than carbon block to prevent clogging. If you run a 1 or 0.5 micron sediment filter, then there's likely no way anything big enough to clog a 5 micron carbon block would get through. Running 5 microns on all is probably okay.

The coconut carbon and GAC are likely fine too. The GAC is not very effective in terms of removing chlorine and VOCs because there's more surface area on a standard carbon block. I would probably replace it with a carbon block when it's exhausted, but it's probably fine to use if it comes with the unit. Just monitor for chlorine breakthrough and change filters accordingly.

With the DI resin, that's a fine way to go. Definitely check with BRS to see which mixed bed you should run. I think you need a different mixed bed if you run single beds as opposed to just running all mixed beds.

 

[CherBear811]

Glad to help

The 5 micron sediment filters and carbon blocks are probably okay. I always prefer to run a smaller sediment filter than carbon block to prevent clogging. If you run a 1 or 0.5 micron sediment filter, then there's likely no way anything big enough to clog a 5 micron carbon block would get through. Running 5 microns on all is probably okay.

The coconut carbon and GAC are likely fine too. The GAC is not very effective in terms of removing chlorine and VOCs because there's more surface area on a standard carbon block. I would probably replace it with a carbon block when it's exhausted, but it's probably fine to use if it comes with the unit. Just monitor for chlorine breakthrough and change filters accordingly.

With the DI resin, that's a fine way to go. Definitely check with BRS to see which mixed bed you should run. I think you need a different mixed bed if you run single beds as opposed to just running all mixed beds.

When I asked them about the DI resin, they said if I am passing through anion and cation, I can use their mixed resin that is the combination of both (not the regular straight blue stuff).

As for the carbon, I will likely be buying all my replacement cartridges from BRS. 3 out of the first 4 carbon cartridges on that page are 1 micron. Not sure which 2 to go with. But I guess I have some time on that. https://www.bulkreefsupply.com/bulk...ms/reverse-osmosis-filters/carbon-blocks.html

I plan on tee-ing off after the carbon stage and before the DI stage for water for myself and my dogs, so I'd like to run the best carbon combo I can.

 

[chipmunkofdoom2]

When I asked them about the DI resin, they said if I am passing through anion and cation, I can use their mixed resin that is the combination of both (not the regular straight blue stuff).

As for the carbon, I will likely be buying all my replacement cartridges from BRS. 3 out of the first 4 carbon cartridges on that page are 1 micron. Not sure which 2 to go with. But I guess I have some time on that. https://www.bulkreefsupply.com/bulk...ms/reverse-osmosis-filters/carbon-blocks.html

I plan on tee-ing off after the carbon stage and before the DI stage for water for myself and my dogs, so I'd like to run the best carbon combo I can.

Right, so BRS sells two mixed bed resins in addition to their single bed cation and anion resins. The standard blue mixed bed still has two resins in it, it just has the color change on the anion resin (the blue beads). The "Pro" series mixed bed has the color change on the cation resin, or the purple beads. The blue mixed bed is good for water where you don't run single beds because the most likely resin to get depleted first is the anion when exposed to RO water. The "Pro" mixed bed is good for single bed setups because the most likely ion to make it through the cation and anion resins has an affinity for the cation (purple) resin. I believe BRS recommends the purple mixed bed, the "Pro" series, for systems with single bed stages (that's what I use in mine). I just wasn't sure if they have a different formula if you're going with half cartridges.

I use the BRS carbon blocks and I use my RO system for drinking water. Their carbon blocks are NSF certified, so I think they're a fine choice for drinking water. I don't think the pore size on the carbon blocks matters much. I run a 0.6 micron sediment, a 5 micron BRS carbon block, then the 1 micron BRS universal carbon block. If you have a small enough sediment filter, the carbon blocks don't have to perform any particulate filtration, so they could really be almost any pore size within reason.

 

[CherBear811]

Right, so BRS sells two mixed bed resins in addition to their single bed cation and anion resins. The standard blue mixed bed still has two resins in it, it just has the color change on the anion resin (the blue beads). The "Pro" series mixed bed has the color change on the cation resin, or the purple beads. The blue mixed bed is good for water where you don't run single beds because the most likely resin to get depleted first is the anion when exposed to RO water. The "Pro" mixed bed is good for single bed setups because the most likely ion to make it through the cation and anion resins has an affinity for the cation (purple) resin. I believe BRS recommends the purple mixed bed, the "Pro" series, for systems with single bed stages (that's what I use in mine). I just wasn't sure if they have a different formula if you're going with half cartridges.

I use the BRS carbon blocks and I use my RO system for drinking water. Their carbon blocks are NSF certified, so I think they're a fine choice for drinking water. I don't think the pore size on the carbon blocks matters much. I run a 0.6 micron sediment, a 5 micron BRS carbon block, then the 1 micron BRS universal carbon block. If you have a small enough sediment filter, the carbon blocks don't have to perform any particulate filtration, so they could really be almost any pore size within reason.

What are your tap tds and how often do you need to replace your sediment cartridge? Also, how do you know when to replace it, other than visual queues?

 

[chipmunkofdoom2]

What are your tap tds and how often do you need to replace your sediment cartridge? Also, how do you know when to replace it, other than visual queues?

My TDS is relatively low, about 187 ppm. I used to replace my prefilters every 6 months, but I added pressure gauges and bought test strips so now I only replace the prefilters as needed. I'm actually going on 16 months on my current sediment filter and carbon blocks. Still no significant drop in pressure, and no chlorine breakthrough.

You can tell when it's time to replace a sediment filter by pressure readings. Put a pressure gauge before and after the prefilters. Once the pressure starts to drop significantly, it's time to change them. You really could go as low as 50 PSI before replacing the sediment filter (which most membranes are rated for) and still be fine. Sediment filters are pretty cheap, so it doesn't cost much to replace them, which is why I lean toward the more frequent replacement. I'll probably replace mine when I see a 10% drop or so. But, I have relatively low pressure to being with.

 

[Glassfish]

I have a vertex RODI unit with the self cleaning feature. I really like it since it self cleans the membrain every few hours it runs and has a tds meter built in so you know when your cartridges need replacing. So far in 4 years I have only had to replace the sediment filter once ! I make about 2 gal everyday for top off so it gets used . It also has a booter pump to increase the yeild of the ro chamberr .I make water at 1:1 waste to yeild where as most systems are 3:1 or 4:1

 

[CherBear811]

I have a vertex RODI unit with the self cleaning feature. I really like it since it self cleans the membrain every few hours it runs and has a tds meter built in so you know when your cartridges need replacing. So far in 4 years I have only had to replace the sediment filter once ! I make about 2 gal everyday for top off so it gets used . It also has a booter pump to increase the yeild of the ro chamberr .I make water at 1:1 waste to yeild where as most systems are 3:1 or 4:1

Do you run multiple membranes to get that 1:1?

 

[chipmunkofdoom2]

I have a vertex RODI unit with the self cleaning feature. I really like it since it self cleans the membrain every few hours it runs and has a tds meter built in so you know when your cartridges need replacing. So far in 4 years I have only had to replace the sediment filter once ! I make about 2 gal everyday for top off so it gets used . It also has a booter pump to increase the yeild of the ro chamberr .I make water at 1:1 waste to yeild where as most systems are 3:1 or 4:1

The final TDS in the system doesn't tell you anything except when your DI resin is depleted. The only way to know when other filters need to be replaced is by replacing them on a schedule or testing pressure and chlorine breakthrough.

Additionally, a 1:1 ratio will kill a TFC membrane prematurely. RO membranes work by concentrating the solids in the source water into the waste water. Without a proper flow of waste water, the solids will deposit on the membrane's surface, eventually clogging the pores and ruining the membrane. A 4:1 ratio wastes 3 more gallons for every gallon of fresh than a 1:1 ratio, but water costs an average of $0.003 per gallon in the US. A 1:1 ratio is saving you less than a cent per gallon of water produced over a proper 4:1 ratio.

 

[CherBear811]

My TDS is relatively low, about 187 ppm. I used to replace my prefilters every 6 months, but I added pressure gauges and bought test strips so now I only replace the prefilters as needed. I'm actually going on 16 months on my current sediment filter and carbon blocks. Still no significant drop in pressure, and no chlorine breakthrough.

You can tell when it's time to replace a sediment filter by pressure readings. Put a pressure gauge before and after the prefilters. Once the pressure starts to drop significantly, it's time to change them. You really could go as low as 50 PSI before replacing the sediment filter (which most membranes are rated for) and still be fine. Sediment filters are pretty cheap, so it doesn't cost much to replace them, which is why I lean toward the more frequent replacement. I'll probably replace mine when I see a 10% drop or so. But, I have relatively low pressure to being with.

Couldn't I just put the pressure gauge after the prefilters and watch for the drop as an indicator?

 

[chipmunkofdoom2]

Couldn't I just put the pressure gauge after the prefilters and watch for the drop as an indicator?

I suppose a more correct description would be to call it a "pressure differential." The pressure after the prefilters will be lower than the pressure before if the sediment filter/carbon blocks are clogged. The difference is the drop I was referring to.

I personally would (and do) have two gauges because your source pressure may not always be constant (unless you have a booster pump, but even then, a gauge before is still useful). If your source pressure is a bit lower tomorrow than it was today, you might assume the drop was due to the prefilters being clogged if you didn't have a gauge before the filters as well.

 

[Opus]

I personally use the spectrapure plus membrane with a .35 micron sediment and 1 micron carbon. My tap tds is usually around 450 and after the RO it is 2. That means I will get around 2200 gallons of 0 TDS water from my DI cartridge.

The self cleaning mentioned will do nothing for our units. It just doesn't really work on our home units. Now getting a bypass for the DI to flush out the tds creep is a good idea.

 

[CherBear811]

Thank you all for the help and the good suggestions. I have a better idea of what I want to do now and feel a lot better about my decisions. Thanks!

 

[Glassfish]

Do you run multiple membranes to get that 1:1?

No it has a booster pump to up the pressure which makes the RO work better

 

[Glassfish]

I personally use the spectrapure plus membrane with a .35 micron sediment and 1 micron carbon. My tap tds is usually around 450 and after the RO it is 2. That means I will get around 2200 gallons of 0 TDS water from my DI cartridge.

The self cleaning mentioned will do nothing for our units. It just doesn't really work on our home units. Now getting a bypass for the DI to flush out the tds creep is a good idea.

the self cleaning in mine is a flush

The final TDS in the system doesn't tell you anything except when your DI resin is depleted. The only way to know when other filters need to be replaced is by replacing them on a schedule or testing pressure and chlorine breakthrough.

Additionally, a 1:1 ratio will kill a TFC membrane prematurely. RO membranes work by concentrating the solids in the source water into the waste water. Without a proper flow of waste water, the solids will deposit on the membrane's surface, eventually clogging the pores and ruining the membrane. A 4:1 ratio wastes 3 more gallons for every gallon of fresh than a 1:1 ratio, but water costs an average of $0.003 per gallon in the US. A 1:1 ratio is saving you less than a cent per gallon of water produced over a proper 4:1 ratio.

The 1:1 ratio is not something I've adjusted it's just how the unit is due to the booster pump . The water savings doesn't really have anything to do with cost more so not wasting unnecessary water I guess .

 

[chipmunkofdoom2]

The 1:1 ratio is not something I've adjusted it's just how the unit is due to the booster pump . The water savings doesn't really have anything to do with cost more so not wasting unnecessary water I guess .

It does not matter if you modified your system to get a 1:1 ratio or if your system has a 1:1 ratio out of the box. If you are not running a thousand dollar commercial RO system, a 1:1 ratio is not correct and will kill your membrane prematurely. How prematurely depends on how dirty your source water is. You could get away with it for quite a while if your source water has relatively low solids. Even still, you are shortening the life of your membrane.