What am I really saving by using two RO membranes versus one? | BRStv Investigates

[Frop]

Frop investigates lol

I do have an extra 5 micron filter which I only ran around 200gallons through... basically I have all my old 5 micron filters that I replaced with much smaller ones because of our high TDS. but last I remember it didn't change the TDS pre RO, plus I don't want to reinstall the 5s either.

 

[Frop]

I do have an extra 5 micron filter which I only ran around 200gallons through... basically I have all my old 5 micron filters that I replaced with much smaller ones because of our high TDS. but last I remember it didn't change the TDS pre RO, plus I don't want to reinstall the 5s either.

I tested the .5 it didn't do any noticeable difference between samples. Each this time were 720's. Sediment filter didn't reduce TDS.

 

[mic209]

Im referring to the plumbing from the city to my house provides 800 TDS. The water softener actually drops that by 130. Then my single membrane drops it another 660+. DI takes the remaining 8-10.

Sorry I don't quite understand what you meant in your first quote to me. What were you doubting?

 

[MARK N]

Just wondering if you knew what configuration a BRS dual membrane, 150 water saver, that was assembled by BRS came in. Do they assemble it in series or parallel?

 

[JamesP]

The 150gpd upgrade kit came with instructions to install and they were instructuons for series. Based on that I am fairly confident they would be preassembled in series as well.

 

[MARK N]

Cool, thanks for your reply!!!

 

[JamesP]

Yup np. Here is the video for reference. Man this is old looking. Brs has come a long way.

 

[Ryanbrs]

I wonder if running a second sediment filter would be of use in this case. Id be curious to see the tds at each stage of the rodi system.

The carbon block and sediment filter will have a very limited impact on TDS. The membrane does all the work : )

 

[Ryanbrs]

Just wondering if you knew what configuration a BRS dual membrane, 150 water saver, that was assembled by BRS came in. Do they assemble it in series or parallel?

All of our dual membranes are configured as water saver in series : )

 

[nbagnardi]

hey @Ryanbrs I'm sold on the idea and going to add a second membrane, i have a question though. the kit that is sold on the website comes with a 75 GPD membrane... i have a 100GPD membrane in there now pushing 80 psi through it. straight zero, but will i mess anything up running 80 psi through the 75 GPD? right now this is my setup.

 

[bif24701]

I went from a 4 stage regular and upgraded all the way to a 6 stage plus with water saver. One of my best investments period.

Use test strips to monitor the carbon blocks. I like that I can completely exhaust a DI canister before changing it out. When I do I always move the second one to the first spot. Same with the carbon blocks. This system saves me HUGE! Plus I make a lot of water for a 300 gallon system at 60 psi.

 

[TankJanitor]

Hopefully, this is the right place to ask . . .

I noticed that on the 5 and 6 stage RO/DI systems the elements are arranged with one sediment filter and then two carbon filters prior to the membrane.

Why use two carbon blocks? Why not two progressively tighter sediment filters, say a 5 micron sediment filter followed by a 1 micron sediment filter and then 1 micron or smaller carbon filter?

I understand that the carbon is binding with chlorine and other VOCs, but wouldn't progressively tighter sediment removal extend the life of the carbon filter's physical filtration ability? Or does the carbon filter's chemical filtration capacity expire more rapidly than it's physical filtration capacity?

I guess what I'm asking is given the relative costs of sediment filters and carbon filters, would it be more cost effective to run a filter set up with 5 micron sediment - 1 micron sediment - 1 micron carbon as opposed to 1 micron sediment - 1 micron carbon - 1 micron carbon?

Clear as mud, right?

 

[Ryanbrs]

Good question. Carbon blocks are not 100% efficient and will allow some of the disinfectants and other contaminants through, particularly if they are on for long periods of time. Not uncommon for them to allow 10-20% through in a fairly short period of time. The second block will act as a polish. Because the first one will continue to remove "some" disinfectant long after it would otherwise be considered depleted it will lengthen the lifespan of the second significantly as well : )

 

[tigé21v]

Sediment filters are relatively cheap. And last much longer than a carbon block of the same pore size, in so far as the intended function of each.
For example, I changed my sediment and carbon blocks all at the same time many months ago. I have a 0.3 micron pleated sediment filter before my two 1 micron carbon blocks. (Well, to be specific, chloramine block followed by a 1 micron carbon block.) Since that time that I replaced all the filters, I have had to change the carbon blocks many times because they are no longer able to do their intended function- to remove chlorine and other contaminants. Yet, I still have the same 0.3 micron sediment filter in place because it's still fulfilling its intended purpose- to remove sediment.
Hope that makes sense.

 

[bif24701]

Hopefully, this is the right place to ask . . .

I noticed that on the 5 and 6 stage RO/DI systems the elements are arranged with one sediment filter and then two carbon filters prior to the membrane.

Why use two carbon blocks? Why not two progressively tighter sediment filters, say a 5 micron sediment filter followed by a 1 micron sediment filter and then 1 micron or smaller carbon filter?

I understand that the carbon is binding with chlorine and other VOCs, but wouldn't progressively tighter sediment removal extend the life of the carbon filter's physical filtration ability? Or does the carbon filter's chemical filtration capacity expire more rapidly than it's physical filtration capacity?

I guess what I'm asking is given the relative costs of sediment filters and carbon filters, would it be more cost effective to run a filter set up with 5 micron sediment - 1 micron sediment - 1 micron carbon as opposed to 1 micron sediment - 1 micron carbon - 1 micron carbon?

Clear as mud, right?

The primary purpose of the carbon block is to remove the chloramines and chlorine because these degrade the RO membrane. Two is better because you have more contact this better chance at getting them all. Everyone should test the waste water for chlorine and chloramines to ensure they are not getting through, this is also how to know when to change them.

 

[Seand03]

Can you guys re visit this with 3 membrains? I got the 2 upgrade kit and it works great but my water bill is still high. Also maybe if you could include how fast you burn through resin if you have a slightly undersized flow restrictor to produce faster with less waist.

 

[Whipples]

In order to get less waste you need to run at a lower waste ratio, a second membrane is still producing the same waste ratio as before. 4:1 waste to product water ratio still exists with a second membrane, what you get is more output from running the first membrane’s brine into the second membrane ultimately giving you two 4:1 membranes working simultaneously.

 

[tigé21v]

Can you guys re visit this with 3 membrains? I got the 2 upgrade kit and it works great but my water bill is still high. Also maybe if you could include how fast you burn through resin if you have a slightly undersized flow restrictor to produce faster with less waist.

I would think that any savings you may see in your water bill would be used towards your increased DI usage.

 

[randyBRS]

Can you guys re visit this with 3 membrains? I got the 2 upgrade kit and it works great but my water bill is still high. Also maybe if you could include how fast you burn through resin if you have a slightly undersized flow restrictor to produce faster with less waist.

I don't think there's really much added value in adding a third membrane, as you would really begin to sacrifice efficiency and filter effectiveness. As it stands with two membranes, the TDS output is an average of both membranes. You very well could run three membranes, however you would have to account for a higher TDS output as well as a shorter life on the third membrane. For folks with low TDS water to begin with, like under 100ppm, then a third membrane may be feasible. However, if you have higher TDS the poorer rejection rate could really start to eat at your DI resin which may not be as cost effective as running two membranes.

There are ways to tweak the efficiency of your dual membrane RODI unit like adjusting the flow restrictor or increasing the incoming pressure. There's several reefers out there that use needle valves or adjustable inline restrictors to dial in the rejection rate and water production ratio. Here's a video we did on increased pressure and how it can affect rejection rate and water production rates. HERE.

-Randy

 

[ThaChad]

Can you guys re-investigate this using a booster pump? I think your final results would be drastically different if you had a booster pump set at 80-100psi. Also if you use the Aquatec 8855 booster pump, in the parallel configuration, It should significantly increase your results as both the pressure and the flow/volume would be increased.

My TDS is over 350, so I am not able to run the Dual membrane in Series. I am going to have to run it in Parallel, correct me if I am wrong, but It's not going to use any more water than a single membrane, but it will make water 2x faster, Correct? Obviously it will only need to run 1/2 as long, but product 2x the waste and 2x the product water. I do have the Aquatec 8855 booster pump and it is set to 90 PSI. So I really shouldn't loose much if any water pressure to the 2nd membrane.

P.S. Do you know if Tannins in the water increase the TDS? We have Tannins and our water while clear coming out of the tap, has a tea color to it if it sits in a glass for an extended period of time and/or you fill up a tub or bucket you can see the tea color. I am wondering if this is why my TDS is soo high, would getting a Tennins filter reduce my incoming TDS or not?

Thanks,

-ThaChad