RO-DI

[anthonygf]

I have a question about the membranes. Do you get the same quality of water from a 100 gallon per day as the 50? My TDS going in is 480 and output is only around 230. I have a dual membrane setup and with 100 gpd each. Would I get a lower TDS from a dual 50 gpd membrane? Thanks in advance for the answer. I also have 60 to 70 psi water pressure. I also have the 3 stage DI resin setup, cation, anion and mixed bed and have a TDS of 2 so I just added another container of anion resin after the other and now down to 1. I am going through the anion quicker than I would like. Any suggestions? Thanks again ReeftoReef friends.

 

[vetteguy53081]

I have a question about the membranes. Do you get the same quality of water from a 100 gallon per day as the 50? My TDS going in is 480 and output is only around 230. I have a dual membrane setup and with 100 gpd each. Would I get a lower TDS from a dual 50 gpd membrane? Thanks in advance for the answer. I also have 60 to 70 psi water pressure. I also have the 3 stage DI resin setup, cation, anion and mixed bed and have a TDS of 2 so I just added another container of anion resin after the other and now down to 1. I am going through the anion quicker than I would like. Any suggestions? Thanks again ReeftoReef friends.

Quality yes, just a different rate of flow and gallon total per day

 

[anthonygf]

Quality yes, just a different rate of flow and gallon total per day

Thanks vetteguy53081.

 

[killerbren]

Reverse osmosis canisters will have a "rejection rate", also sometimes called a "reduction rate". This should be in the 99 to 95% range. So if a filter had a 95% rate, and you started with 100 ppm tds, you should be left with 5ppm tds after the membrane. If you aren't getting this, make sure your water pressure is good. If the pressure is good it may be time to replace the membrane. Do you have a carbon block before the membrane? Chloramines are pretty brutal on membranes.

 

[anthonygf]

Reverse osmosis canisters will have a "rejection rate", also sometimes called a "reduction rate". This should be in the 99 to 95% range. So if a filter had a 95% rate, and you started with 100 ppm tds, you should be left with 5ppm tds after the membrane. If you aren't getting this, make sure your water pressure is good. If the pressure is good it may be time to replace the membrane. Do you have a carbon block before the membrane? Chloramines are pretty brutal on membranes.

I have 60 to 70 psi water pressure, the membranes about 2 months old. Yes, also a whole house carbon filter that stands 4.5 feet tall, several other carbon filters before and after the membranes. I noticed this really bad smell from the new membranes when flushing them, that is why I added a carbon filter after the membranes. So my membranes are only cutting my tds in half basically, and I made sure it is installed correctly. They have been setup for 7 years and change filters when needed. Thanks for your help.

 

[Kristopher Conlin]

I have around 500tds out of the tap. I was burning resin like crazy until I got a booster pump and switched to separate cation and anion resins. Before the booster I was at 65 psi and would regularly be outputting 25 tds into the resin. Now at 85psi I float around 12 tds. I produce water significantly faster as well which is a nice bonus.

 

[Kristopher Conlin]

My understanding was that higher flow rate membranes reject slightly less. It still seems that putting 480 tds in and getting 230 tds out is unusual. What brand of RO do you have? And what are the pre-filter to the membranes set up like?

I run a sediment filter followed by two carbon blocks. Then into the membranes.

 

[anthonygf]

I have a whole house carbon and sediment filters, carbon filter is 4 feet tall and is self cleaning. Still after 12 years is still doing it's job dropping the chlorine down to 2. I also have several carbon filters before and after the membrane and zero chlorine to the membranes. I have two sediment filters, one for the booster pump and one for the membrane. I don't use the booster pump anymore because I installed a whole house water pressure booster pump and is set at 65-70 psi. from the city is only 40 psi. At this moment I am installing a small water softener made for espresso machines for the membranes, I also have a water softener for the house but still have some calcium left after treatment. Am I going to far? lol..

 

[Opus]

You definitely have an issue but hard to say where. First I would invest in a handheld tds meter if you don't already have one. I see reports of the internal ones failing, plus it is hard to set them up to read at different points. No need to worry about the prefilters for trouble shooting at this point, they don't do anything for tds. My first question is where are you measuring the 230 tds out. Is this after the second membrane? I would be interested in knowing the tds after the first membrane. If it is OK then we know the second membrane is probably the issue.

 

[anthonygf]

You definitely have an issue but hard to say where. First I would invest in a handheld tds meter if you don't already have one. I see reports of the internal ones failing, plus it is hard to set them up to read at different points. No need to worry about the prefilters for trouble shooting at this point, they don't do anything for tds. My first question is where are you measuring the 230 tds out. Is this after the second membrane? I would be interested in knowing the tds after the first membrane. If it is OK then we know the second membrane is probably the issue.

Good idea, I will test the tds after the first one. I have several handheld tds meters plus the ones installed on the unit for before and after membranes and one after DI filters which is at 1.

 

[killerbren]

Just for reference, I have about 150ppm going into the membrane and 3ppm coming out the other side, so if yours is only taking 50% out there is an issue there. Sounds like your pressure is fine.
When the membranes come new there is a flow restrictor that comes with them that slides into the tubing prior to the membranes to set the correct flow rate. Is this in? Can you verify you are getting the proper amount of gallons per day somehow? Just to rule out too much flow. if your resin is depleting fast i would say your current meter Is correct, plus it sounds like you have a few meters to verify. For reference I can probably get 200-250 gallons of rodi water on 1 canister of resin (just guessing).
My only thoughts are maybe you got a dud, is it possible it dried out prior to install? Maybe packaged or stored incorrectly?

 

[anthonygf]

I have a flow restrictor #800 on the waste side. Are you saying it should be placed on the inlet? A dud membrane? That is a possibility. I just purchased 2 more but at the 50 gpd which I haven't installed yet.

 

[killerbren]

I have a flow restrictor #800 on the waste side. Are you saying it should be placed on the inlet? A dud membrane? That is a possibility. I just purchased 2 more but at the 50 gpd which I haven't installed yet.

Hmmmm, I'm not sure, it's been a while since I changed membranes. Might be wise to double check but you are probably correct.

 

[killerbren]

You were right, restrictor goes on the waste side but you might be undersized. If you have a 100 gallon per day, the charts are calling for a #1000. A smaller restrictor will let more tds through, but im not sure how much. I dont think 1 size off optimal will push your efficiency down to 50%, but might be worth looking up.

 

[anthonygf]

You were right, restrictor goes on the waste side but you might be undersized. If you have a 100 gallon per day, the charts are calling for a #1000. A smaller restrictor will let more tds through, but im not sure how much. I dont think 1 size off optimal will push your efficiency down to 50%, but might be worth looking up.

BRS calls for #800 but I will try a 1000. Just checked BRS only goes up to 800 and that has been discontinued. They only have up to 550 now.

 

[anthonygf]

Thank you all for helping me out. Time to eat dinner and go to bed. Will check on my system tomorrow.

 

[anthonygf]

You were right, restrictor goes on the waste side but you might be undersized. If you have a 100 gallon per day, the charts are calling for a #1000. A smaller restrictor will let more tds through, but im not sure how much. I dont think 1 size off optimal will push your efficiency down to 50%, but might be worth looking up.

Just purchased a 1000cc on Amazon 2 for $8.

 

[Justdrew]

In general Dow Filmetc 75 GPD are the most efficient filter. They typically have a rejection rate of 98%-99%. the Dow Filmtec 100 GPD only have a rejection rate of 92%-94%. There is a difference between membranes.

 

[ying yang]

RO/DI Basic Guide

There are always a lot of questions regarding which RO/DI setup do I need, how many stages, how do I know when to change filters/membranes, I’m getting a weird TDS value, etc. Hopefully this clarifies a few things and helps some of you out one day. My first recommendation would be to find the...

www.reef2reef.com

Not sure if got the answers you want in this,but maybe give this a read.
Seems like you getting nearly 50% reduction after your membrane so something clearly up.
My first thought,was the membranes fully inserted so the water going through the membranes and not bypassing,second thought was your in-house carbon 4 foot thing,its few years old you say but is this letting any fines through or something like this.
Then 3rd thought was what membranes you actually using,are they good ones kind of thing and then was have you got correct restrictor in,and i read often 80-90 psi is a good psi to aim for so if you got the booster pump maybe give that a try to just install on rodi unit.I'm a plumbing and heating engineer but not a rodi expert as only fitted and used my own and fit a few just small ro units under a sink in past.
So no expert as I say as knowledge on rodi units pretty limited tbh.
Good luck and hopefully you get to bottom off your problem.

 

[KStatefan]

With source water tds as high as yours is I would not use a dual membrane set up. Dow has been making a lot of changes to their membranes and I think that the TW30-1812-50HR has the highest specified rejection rate now