RODI flushing...

[afboundguy]

Does flushing the RO membrane every hour actually make a difference or does it just waste water? I know flushing it at the beginning is a good thing especially if the system doesn't run for several days but even with that a pre-resin flush seems more beneficial to combat TDS creep issues.

I now have the Smart Buddie that just flushes the RO membrane for about a minute when it turns on. I used to have Hydros solenoids that would auto-flush the RO membrane every hour for about a minute but with the Smart Buddie it doesn't flush hourly and I'm curious if there is a benefit from doing the flush every hour vs just at the beginning?

 

[jasonrusso]

I purge the wastewater at the start so I don't deplete my DI resin. I have a TDS probe before the resin and I wait until it's under 10 before I close the flush valve.

I pretty much never flush out the ro membrane.

 

[Red_Beard]

Depends on how high your TDS is and how long you run it for. If you had really high TDS and/or you ran it for many hours at a time, that extra flush could help prolong your membrane a bit, but we are talking like HIGH TDS. The membrane should get plenty of flow through to flush solids during normal operation under normal circumstances. That, and you should be replacing it every year or so anyhow.

 

[jasonrusso]

Depends on how high your TDS is and how long you run it for. If you had really high TDS and/or you ran it for many hours at a time, that extra flush could help prolong your membrane a bit, but we are talking like HIGH TDS. The membrane should get plenty of flow through to flush solids during normal operation under normal circumstances. That, and you should be replacing it every year or so anyhow.

Why do you change it? What do you see?

I'm probably 3-4 years on mine. I have 150 going in, 2 coming out.

 

[Red_Beard]

Why do you change it? What do you see?

I'm probably 3-4 years on mine. I have 150 going in, 2 coming out.

150 is pretty low TDS, that definitely prolongs your membrane life and unless you are running it multiple days on end, you probably don't need any additional flush cycles.
I have noticed despite TDS readings, that regular replacement of the membrane has a visual impact on some of the finer colors and polyp extension of my acros. If that isn't something you are focused on, you are probably good to run yours longer.

 

[jasonrusso]

150 is pretty low TDS, that definitely prolongs your membrane life and unless you are running it multiple days on end, you probably don't need any additional flush cycles.
I have noticed despite TDS readings, that regular replacement of the membrane has a visual impact on some of the finer colors and polyp extension of my acros. If that isn't something you are focused on, you are probably good to run yours longer.

150 is low? I'm afraid to drink it

I know some people on wells are in the 400s.

 

[slingfox]

Why do you change it? What do you see?

I'm probably 3-4 years on mine. I have 150 going in, 2 coming out.

It is common practice to change the filters and/or membrane when TDS coming out at the end shows anything other than zero. 150 TDS from the tap is pretty low so you are lucky there.

 

[Red_Beard]

150 is perfect for drinking!
I mean some muni's are running up in the 6-700s... could be MUCH worse :)

 

[jasonrusso]

It is common practice to change the filters and/or membrane when TDS coming out at the end shows anything other than zero. 150 TDS from the tap is pretty low so you are lucky there.

It's town water.

When the water after the DI is above zero, I change the filters and resin. I don't necessarily change the RO membrane. If it's still filtering out 98%, why change it?

 

[MegabiteOG]

In AZ I had over 400. Here in GA I get 70 - 80 out of the tap.

 

[jasonrusso]

150 is perfect for drinking!
I mean some muni's are running up in the 6-700s... could be MUCH worse :)

I only drink the water after my refrigerator carbon filter. I've never tested it

 

[jasonrusso]

In AZ I had over 400. Here in GA I get 70 - 80 out of the tap.

400 out of the tap? Town water?

 

[slingfox]

It's town water.

When the water after the DI is above zero, I change the filters and resin. I don't necessarily change the RO membrane. If it's still filtering out 98%, why change it?

If the RO membrane is rejecting 96-99% it is theoretically fine. Some hobbiest and coral growers (eg, SBB Corals) change membranes more often since they believe that helps their coral look better. SBB bases their membrane changes on volume of water processed but that is tied to the quality of their input water so every one would need to figure out what works for them.

 

[jasonrusso]

It's town water.

When the water after the DI is above zero, I change the filters and resin. I don't necessarily change the RO membrane. If it's still filtering out 98%, why change it?

If the RO membrane is rejecting 96-99% it is theoretically fine. Some hobbiest and coral growers (eg, SBB Corals) change membranes more often since they believe that helps their coral look better. SBB bases their membrane changes on volume of water processed but that is tied to the quality of their input water so every one would need to figure out what works for them.

I'm not growing or selling anything.

If my existence depended on growing corals I might have a very different outlook. If a $75 membrane was the difference between a good or bad grow, it's a no brainer.

 

[slingfox]

I'm not growing or selling anything.

If my existence depended on growing corals I might have a very different outlook. If a $75 membrane was the difference between a good or bad grow, it's a no brainer.

See the 15 minute mark here for discussion on changing RO membrane. Whether this is right or wrong I don’t know but interesting data point:

 

[MegabiteOG]

400 out of the tap? Town water?

Yes, 400 to 450. I had hauled water. I ran a dual tank Kinetico to clean it out before it getting into the house.

Although I have super low TDS here in GA, I run a lot of stages. I checked with the municipality and they use chloramines and other stuff you don’t want in the tank. In my opinion, a very good RO/DI is a really cheap investment relative tothe cost of everything else for piece of mind regardless of incoming TDS. Changing filters is pretty cheap too.

 

[fish_collector]

150 is low? I'm afraid to drink it

I know some people on wells are in the 400s.

150 is perfect for drinking!
I mean some muni's are running up in the 6-700s... could be MUCH worse :)

400, 600, 700 TDS? I can only dream of TDS that low from the tap. For the last 6 months my softened tap water TDS has been 1000-1100, I'm in Phoenix. It used to float around 900 but the city sources it's water from different aquifers at different times of the year and presently it's the highest I've seen it in 20 years. I run filmtek membranes and I get excited when my post membrane number is 40 or less.

 

[jasonrusso]

400 out of the tap? Town water?

Yes, 400 to 450. I had hauled water. I ran a dual tank Kinetico to clean it out before it getting into the house.

Although I have super low TDS here in GA, I run a lot of stages. I checked with the municipality and they use chloramines and other stuff you don’t want in the tank. In my opinion, a very good RO/DI is a really cheap investment relative tothe cost of everything else for piece of mind regardless of incoming TDS. Changing filters is pretty cheap too.

Right, but the chlorine should be filtered out by the carbon stages. It also doesn't show up on a TDS probe.

 

[KStatefan]

I have never flushed my membrane on my system at home. I do run a DI bypass y every time the system runs and the TDS creep is sent down the drain. I do not think flushing does anything except in a few cases. The membrane is being flushed constantly while running to keep impurities from reaching saturation point and depositing scale on the membrane. One scale is formed on the membrane a city water pressure flush is not going to remove it.

Current membrane is almost two years old I will run it until the rejection drops below 97.5%

 

[afboundguy]

Depends on how high your TDS is and how long you run it for. If you had really high TDS and/or you ran it for many hours at a time, that extra flush could help prolong your membrane a bit, but we are talking like HIGH TDS. The membrane should get plenty of flow through to flush solids during normal operation under normal circumstances. That, and you should be replacing it every year or so anyhow.

I have around 350 TDS going in.

I have never flushed my membrane on my system at home. I do run a DI bypass y every time the system runs and the TDS creep is sent down the drain. I do not think flushing does anything except in a few cases. The membrane is being flushed constantly while running to keep impurities from reaching saturation point and depositing scale on the membrane. One scale is formed on the membrane a city water pressure flush is not going to remove it.

Current membrane is almost two years old I will run it until the rejection drops below 97.5%

I have a TDS meter before and after the RO membranes and I never really thought to track rejection rate to guage when to change the RO membranes but I will easily track that now!