So I have a 5 stage RODI. This morning, I changed all my filters cause my tds was 0.01 and my resin looked like it was exhausted (all orange). I started making new water and my first 5 gallon batch came as a tds of 0.03. I figured maybe since it was the first batch, it wasnt completely clean so i tossed it and made a new 5 gallon batch with a different container and it still came out 0.03 tds. I checked my tds meter with my older rodi water and it read 0.01. The new filters have been laying around for a few months. Ive changed filters 3-4 times already and never had this problem. Any thoughts?
RODI filters
- Thread starter Jet915
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PatW
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On my 5 stage BRS RODI, my first filter is a sediment filter. The next two filters are carbon blocks. They absorb chorine from the city water. Chlorine will damage the RO membrane. None of these will reduce the TDS. The fourth stage is the RO membrane. My water goes into the RO at about 140 tds and out at 2 tds. The last stage is my DI resin. The DI resin takes the 2 tds down to 0 tds. But it will deplete. When it is depleted, I repack the cylinder. Well actually I have added another DI cylinder. When the first DI membrane depletes, I move DI cylinder #2 and put it in the #1 position, repack the depleted cylinder and put it in the #2.
Jet915
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The resin is the last stage. I just change all my filters at the same time, it makes it easier to remember. Shouldnt the tds be back to 0? Ive done this a few times in the past and never had this problem.....
You want to change you filters in stages by taking out all of your other filters, including the RO membrane. If you can bypass your DI resin you want to do that and just have water coming out the RO otherwise remove resin as well.
So first run the sediment filter alone for maybe 5 minutes. This will remove any glue and binders in the filter which can clog your carbon and RO
Next run just the carbon blocks. Lots of carbon fines will come out. Run that until it’s clear.
Then you can add your RO back. I usually measure tds at this point and wait until I hit target of 98% of my source TDS. After that your can go thru the Resin without worrying about depleting it quickly.
The mostly likely source of the high tds at this point is the Carbon fines if you didn’t flush that.Id recommend removing the RO and DI, flushing it for a little, then add back the RO, and flush that to remove and carbon in it till your TDS comes back down.
So first run the sediment filter alone for maybe 5 minutes. This will remove any glue and binders in the filter which can clog your carbon and RO
Next run just the carbon blocks. Lots of carbon fines will come out. Run that until it’s clear.
Then you can add your RO back. I usually measure tds at this point and wait until I hit target of 98% of my source TDS. After that your can go thru the Resin without worrying about depleting it quickly.
The mostly likely source of the high tds at this point is the Carbon fines if you didn’t flush that.Id recommend removing the RO and DI, flushing it for a little, then add back the RO, and flush that to remove and carbon in it till your TDS comes back down.
Is that 3 tds after the resin? If so the resin is dead. If that’s after the RO, then that’s great. If you measure the tds after the RO, and it’s really high, there’s a problem with your membrane.
I learned this lesson the hard way. I wasn't flushing before use, now I turn on my inline TDS meter, turn on water source, flush everything until TDS reads 0, then I make a fresh batch of water. I have a flush valve which makes the flushing process take about 3-5 minutes. If you don't have a flush valve, it could take longer...
Jet915
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So I took out the water from all the cannisters and reattached everything. So the TDS after the RO membrane is 50, after the resin its now 1-2 which is a little better. Is 50 a normal tds reading after the RO membrane (stage 4)? The only other thing is I changed the filters for stage 1-3 and the resin but I didnt change the RO membrane could that be the issue? I think I changed the RO membrane last time and thought you dont have to change that one often (could be wrong).
50 ppm tds for RO water is waaaaaaay too high. Some potential causes:
Russ
- TDS testing error
- Bad meter
- You tested TDS creep water rather than letting the RO run for 120+ seconds before taking measurement
- feedwater in excess of 1000 ppm
- flush valve open causing very low pressure @ the RO membrane
- clogged prefilter (s) causing very low pressure at the membrane
Russ
As always, we're available to troubleshoot with you. Give us a call when you're in front of your system. We're here today. Our first questions will be:
What is your tap water TDS
What is your RO water TDS
What is your DI water TDS
What is your gauge pressure when the system is running
Russ
513-312-2343
What is your tap water TDS
What is your RO water TDS
What is your DI water TDS
What is your gauge pressure when the system is running
Russ
513-312-2343
OK - so 48/959 = 0.05, or 5%. 5% of the feedwater TDS is getting through the membrane, so 95% is getting rejected.
A booster pump would help you. With that feedwater TDS, and assuming you are using a Filmtec membrane, you'd want 60+ psi. Remember the rule of thumb that for every 100 ppm TDS over spec, you'll need 1 psi extra pressure just to break even.
A booster pump would help you. With that feedwater TDS, and assuming you are using a Filmtec membrane, you'd want 60+ psi. Remember the rule of thumb that for every 100 ppm TDS over spec, you'll need 1 psi extra pressure just to break even.
So Dow membrane says 50psi at 250ppm. I’m at 950. Therefore I would need 57PSi to make it work properly.
If I then got an optimistic 98% rejection rate. I would have a TDS of around 20 after RO and get about 200ish gallons of water before exhausting my RO. Basically doubling my Life expectancy of resin. Ballpark figures sound right? Will going higher than 60 help?
about 250 gallons per DI cart. Going with higher pressure will help, but not much. Once you get up above the factory spec, or in your case 57 psi, the improvement in rejection caused by higher pressure is minimal.
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