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

[randyBRS]

Hey guys!

Another episode of BRStv Investigates is finally here!

Today, we put some testing and numbers behind a single DOW Filmtec 75gpd RO Membrane versus two RO membranes and see just how much of an upgrade it is! Along with that, Ryan explores the differences between plumbing multiple membranes in series or parallel and the results are pretty surprising!

-Find all of our reefing videos HERE!

 

[Khh27]

So I run 77-80psi with a booster pump on the 150gpd kit. will that drastically change results? or will anything over 65psi run same results.

 

[Vanmo92]

Ive got an extra membrane laying around so Im probably going to order another housing and run it in series. Im wondering though with 2 membranes would I use 2 flow restrictors? Or take the existing one out before I run the waste into the 2nd membrane and then only use a flow restrictor after the 2nd membrane?

 

[mic209]

I did the 150gpd upgrade to my BRS RO unit and within a few short months the second membrane was shot, it wouldn't produce anything below 20 TDs. My tap water TDS is around 300 and it gets 80 psi. I spoke with BRS and they recommended I not do anymore. I spoke with another RO company and they said it will work, as long as I'm okay with replacing RO membranes every few months rather than every few years. So I am now
back to a single membrane. It's a waste of money in my opinion.

 

[-Logzor]

I did the 150gpd upgrade to my BRS RO unit and within a few short months the second membrane was shot, it wouldn't produce anything below 20 TDs. My tap water TDS is around 300 and it gets 80 psi. I spoke with BRS and they recommended I not do anymore. I spoke with another RO company and they said it will work, as long as I'm okay with replacing RO membranes every few months rather than every few years. So I am now
back to a single membrane. It's a waste of money in my opinion.

Are you sure it just wasn't exhausting your DI resin? I've run the dual system for years and don't have to replace the membranes very often. Maybe every 2-3 years. But I do go through resin faster.

 

[Ryan Browne]

Ive got an extra membrane laying around so Im probably going to order another housing and run it in series. Im wondering though with 2 membranes would I use 2 flow restrictors? Or take the existing one out before I run the waste into the 2nd membrane and then only use a flow restrictor after the 2nd membrane?

You need to remove all of your current flow restrictors and purchase a new one. You will ONLY need 1 flow restrictor. Some flow restrictors are placed inside the RO tubing. I like the external restrictors with a flush valve on it.

 

[Ryanbrs]

So I run 77-80psi with a booster pump on the 150gpd kit. will that drastically change results? or will anything over 65psi run same results.

Higher PSI has a significant impact on product water flow rates. Check out this investigates : )

 

[mic209]

Are you sure it just wasn't exhausting your DI resin? I've run the dual system for years and don't have to replace the membranes very often. Maybe every 2-3 years. But I do go through resin faster.

Oh it exhausted both my DI resins too that were both newer when I started the dual membrane. I only use spectarpure maxcap and silica buster DI, so they're not cheap to replace. But the second membrane was no longer rejecting 98-99% of the TDS. Have you measured TDS before and after each membrane to see if you're getting the correct rejection rate? The other question would be if the extra cost of frequently replacing DI is cheaper than the extra water.

 

[Ryanbrs]

I did the 150gpd upgrade to my BRS RO unit and within a few short months the second membrane was shot, it wouldn't produce anything below 20 TDs. My tap water TDS is around 300 and it gets 80 psi. I spoke with BRS and they recommended I not do anymore. I spoke with another RO company and they said it will work, as long as I'm okay with replacing RO membranes every few months rather than every few years. So I am now
back to a single membrane. It's a waste of money in my opinion.

Sorry to hear about your experience. 300 is approaching that range where we would not recommend it because the waste is likely going to come out around 400. One of the things you can do in this case is install an auto flush and potentially a slightly larger flow restrictor. May not be worth it depending on your needs.

 

[Ryanbrs]

Ive got an extra membrane laying around so Im probably going to order another housing and run it in series. Im wondering though with 2 membranes would I use 2 flow restrictors? Or take the existing one out before I run the waste into the 2nd membrane and then only use a flow restrictor after the 2nd membrane?

you only use the restrictor on the second one : )

 

[Bryan MD]

I have had my ro/di unit running for a year and I like the idea of reducing waste water. When I make the upgrade, should I replace my ro liner when I add the second unit or just wait it out. I'd think to do them at the same time note in in my log so I can check in a couple years when to replace both. thoughts???? Should flush valves be replaced every so often?

 

[star fawkes]

My booster pump and 150gpd upgrade gets delivered today. Very excited for it.

 

[NeverlosT]

Oh it exhausted both my DI resins too that were both newer when I started the dual membrane. I only use spectarpure maxcap and silica buster DI, so they're not cheap to replace. But the second membrane was no longer rejecting 98-99% of the TDS. Have you measured TDS before and after each membrane to see if you're getting the correct rejection rate? The other question would be if the extra cost of frequently replacing DI is cheaper than the extra water.

I think it is crucial that you flush your membranes every time you exercise the system with dirty input water.

It would be interesting to hear what your TDS from each membrane was before and after the mod. I just changed to running in series a few hundred gallons ago, I'll check the TDS coming from each membrane. If the average TDS from the two membranes isnt much higher than running one membrane, then DI resin consumption shouldnt be much more.

 

[NeverlosT]

You need to remove all of your current flow restrictors and purchase a new one. You will ONLY need 1 flow restrictor. Some flow restrictors are placed inside the RO tubing. I like the external restrictors with a flush valve on it.

I understand that you will only need one flow restrictor and locate it on the waste line of the second membrane, but can you elaborate why one would need to buy a new one? Why not just move the flow restrictor you have? We arent trying to speed up water through the membranes, we are just trying to keep pressure high in each and combine their outputs. Please explain?

 

[mic209]

Sorry to hear about your experience. 300 is approaching that range where we would not recommend it because the waste is likely going to come out around 400. One of the things you can do in this case is install an auto flush and potentially a slightly larger flow restrictor. May not be worth it depending on your needs.

Yes I'm over the water saving part, lol. But since I have the spare housing, do you think 80 psi is enough to run them parallel to speed up production?

 

[Ryanbrs]

Yes I'm over the water saving part, lol. But since I have the spare housing, do you think 80 psi is enough to run them parallel to speed up production?

almost certainly : )

 

[Honor Israel]

My tap TDS is 272 which is under 300, is it advisable for me to run dual RO? Or will I burn up the membrane to fast?

Would 10-12 tds after second ro membrane be to high?

There are post that say the second membrane will not last as long because its not getting a 4:1 rinse as instructed by manufacture of membrane.

city water
chlorine
no chloramine
80 psi
no water softener

 

[dragon99]

Thanks for this as always.

Sorry to hear about your experience. 300 is approaching that range where we would not recommend it because the waste is likely going to come out around 400. One of the things you can do in this case is install an auto flush and potentially a slightly larger flow restrictor. May not be worth it depending on your needs.

My input is ~250 tds, so I'm close to that range where it might not make sense. So far I'm getting 3-4tds out of a dual membrane water saver setup. I guess I'll have to see how long I get before the second membrane starts failing.

What flow restrictor would you recommend? I'm currently running the 550ml and have a really low ro:waste ratio of 0.8:1
I flush before and after making water. Does the autoflush do something different? Or just automate that process.

 

[Honor Israel]

Thanks for this as always.


My input is ~250 tds, so I'm close to that range where it might not make sense. So far I'm getting 3-4tds out of a dual membrane water saver setup. I guess I'll have to see how long I get before the second membrane starts failing.

What flow restrictor would you recommend? I'm currently running the 550ml and have a really low ro:waste ratio of 0.8:1
I flush before and after making water. Does the autoflush do something different? Or just automate that process.

Looks like you are getting 99% rejection, thats amazing. I only get 96.5-97% rejection.

Are you using membrane from BRS?

 

[Reef man 89]

Another great video from Ryan and the BRS team!!