Rodi winter question

Fishingandreefing · Jan 17, 2022

So I have an Aquaticlife 4 stage rodi 100GPD unit. So is that mean under ideal circumstance, it produces 100g rodi in 24 hours correct? (1.2 hours per 5g bucket)

I am running the aquaticlife booster pump unit. During summer time, it only takes about 50mins per 5g bucket. Now during winter here 25-45 degree, usually takes 85mins (35min more).

I know it’s normal during winter time but I am skeptical if I need to change out my RO membrane. It’s one year old and it’s tds reading without DI is at around 12. (I make about 45g rodi weekly).

just want to see if I need to change it. Aquaticlife recommends change it out 1-2 years. Don’t really want unless I have to, it’s $50 lol and it’s so slow annoys me.

thanks

GaryE · Jan 17, 2022

sounds about right.. I can make 32 gallons during the summer in about 6 hours but in the winter it's about 12-14.. my TDS going in is about 375-420 and coming out of the RO is about 9..

Gtinnel · Jan 17, 2022

What is the tds of your source water? I go by the decrease in rejection rate to know when to replace the membrane. Usually when the water is colder in the winter your production rate goes down but the rejection rate goes up. For me I get 1 ppm after the membrane in the summer in the winter it drops to 0 after the membrane.

LeftyReefer · Jan 17, 2022

What is the TDS of your source water?
an RO membrane, when operating correctly, should reject about 98% of TDS.
So 12 TDS is 2% of 600.
So if your source water TDS is around 600, then your RO is operating as it should.
If your source water TDS is lower than that, then maybe an RO membrane change is needed.

Colder water slows down the RO membrane (takes longer to process water) but it actually helps the RO membrane reject more TDS...

Opus · Jan 17, 2022

As already stated, we would need to know your tap tds to know how well the membrane is working. A membrane should last 5 to 7 years if you take care of it.

LeftyReefer · Jan 17, 2022

Gtinnel said:
For me I get 1 ppm after the membrane in the summer in the winter it drops to 0 after the membrane.

Same here.

My RO membrane rejects closer to 100% of TDS during the winter months when my incoming source water is a lot colder. It takes longer to produce a batch of RO/DI water, but my RO membrane works better. I barely have to use my DI resin during winter.

Gtinnel · Jan 17, 2022

LeftyReefer said:
Same here.

My RO membrane rejects closer to 100% of TDS during the winter months when my incoming source water is a lot colder. It takes longer to produce a batch of RO/DI water, but my RO membrane works better. I barely have to use my DI resin during winter.

Even with dual membranes di lasts me forever regardless of season. I think I've replaced it once in the last 2 years. I'm considering adding a third membrane.

Fishingandreefing · Jan 17, 2022

Source water is at around 165. After RO membrane is 12 and 0 with DI.

KStatefan · Jan 17, 2022

Fishingandreefing said:
Source water is at around 165. After RO membrane is 12 and 0 with DI.

Should be better then that.

Gtinnel · Jan 17, 2022

Fishingandreefing said:
Source water is at around 165. After RO membrane is 12 and 0 with DI.

That's about 93% rejection which is bad. It seems like it's time for a new membrane. Did your tds after the membrane use to be lower?

Fishingandreefing · Jan 17, 2022

KStatefan said:
Should be better then that.

What do you mean?

LeftyReefer · Jan 17, 2022

Fishingandreefing said:
Source water is at around 165. After RO membrane is 12 and 0 with DI.

Then something is not right...
Can't say if the RO membrane is toast, but it isn't operating at anywhere near the efficiency it should be....

Make sure it is installed correctly. (inserted until you hear a pop/click)

KStatefan · Jan 17, 2022

Fishingandreefing said:
What do you mean?

You membrane should be rejecting more of the TDS then it is.

Fishingandreefing · Jan 17, 2022

Gtinnel said:
That's about 93% rejection which is bad. It seems like it's time for a new membrane. Did your tds after the membrane use to be lower?

It should be lower after the membrane but I can’t be sure.

Fishingandreefing · Jan 17, 2022

KStatefan said:
You membrane should be rejecting more of the TDS then it is.

Got you. So I guess if is at around 3-5 should be good?

LeftyReefer · Jan 17, 2022

with incoming source water TDS of 165, then you shouldn't be seeing more than 3-5 TDS out of your RO membrane. (98% rejection)

You said you were getting 12 out of the membrane, which would indicate an issue somewhere.

Gtinnel · Jan 17, 2022

The reason I asked if your tds used to be lower was to try and rule out installation issues. If your membrane is installed correctly then yes it sounds like you need a new membrane.

Fishingandreefing · Jan 17, 2022

Thanks for all the help. Flushing my membrane now for about 8 hours that should be 30g per aquaticlife recommendation. According to them, if I don’t do that well, it will burn DI filter a lot quicker.