At my wits end: DI Nightmare

Miami Reef · Mar 23, 2023

This happens like clockwork. After my DI starts getting exhausted (TDS reads 1-2ppm), I change it.

I pack it VERY, VERY tightly. I have a glass jar that I compress the di.

I changed all my filters (Sediment filters, carbon, membrane, and DI resin). Yes, I correctly flushed my Carbon and membranes.

The first week of using my new filters (made 30 gals), I was getting 0ppm tds. After the membrane was about 6-7ppm

After a week, the TDS after the membrane was around 40ppm (after running), and after the DI was 30ppm. THE DI IS BRAND NEW!!! No color change at all.

Usually, when this happens, I need to remove the DI and try messing with it to get it to reread 0ppm.

But why is my TDS after membrane reading high all of a sudden? I just changed it a week ago, and it was perfect. I live in the city, and we don’t use well water.

Why does my DI TDS always read high after a week after installation??!

We had a pretty big party at home last night. Could the CO2 be contributing to this? I’m lost and pretty frustrated.

Lbrdsoxfan · Mar 23, 2023

Simple one, how old is the membrane? I don't see that one out there. Whats your tds coming into the membrane?

Its cool man, relax. Remember you are running a large tank, so your gonna exhaust everything much quicker than most.

Nah co2 wont have anything g to do with that, maybe low ph but eh....

Miami Reef · Mar 23, 2023

Lbrdsoxfan said:
how old is the membrane?

1 week old

Miami Reef · Mar 23, 2023

Lbrdsoxfan said:
Whats your tds coming into the membrane?

About 160ppm

Lbrdsoxfan · Mar 23, 2023

Check how the membrane is seated, could be bypassing from not being loaded well. Any clue on rejection rate? Hell could even be a bad membrane.

Miami Reef · Mar 23, 2023

Lbrdsoxfan said:
Check how the membrane is seated, could be bypassing from not being loaded well. Any clue on rejection rate? Hell could even be a bad membrane.

It’s from my LFS. It doesn’t even state the rejection rate, but it’s 100 GPD.

I am going to try and get a good one, but my main issue is the DI. Why does it suddenly shoot high tds after a week of installing it? I always thought maybe it was channeling, but I could not have packed it tighter.

Snoopy 67 · Mar 23, 2023

I would try Spectrapure for a new membrane, flow restrictor & a MaxCap DI. Then you can see if it's really worth doing your own.

thatmanMIKEson · Mar 23, 2023

no r.o membrane should have that bad of a rejection rate. I have over 200-300+ incoming and never hits 5tds after the brane. Actually I see 4 and it drops to 3 then I will start processing it through the d.i which is probably a 10min flush. But you should be way lower .

I would definitely check that you have the correct flow restrictor, and the membrane is the correct size and seated well.

I have 150g per day unit but it uses 2×75gpd filters are you sure you have the correct membrane? Something is going on?

thatmanMIKEson · Mar 23, 2023

Miami Reef said:
It’s from my LFS. It doesn’t even state the rejection rate, but it’s 100 GPD.

I am going to try and get a good one, but my main issue is the DI. Why does it suddenly shoot high tds after a week of installing it? I always thought maybe it was channeling, but I could not have packed it tighter.

I dont pack it with something just tap it on the table as you put in a little at a time, tap tap tap

exnisstech · Mar 23, 2023

I had this exact problem when I installed a new system and found I had installed the membrane backwards.
I like to run more than one chamber of di resin also. This way when the first one starts to go the second (I actually have 4) will pick up the slack and you'll still have 0 tds so you can finish what your doing and not have to stop to change resin. I rarely have to change the resin after the first chamber if I change that one as soon as I start to see any tds.

Lbrdsoxfan · Mar 23, 2023

thatmanMIKEson said:
no r.o membrane should have that bad of a rejection rate. I have over 200-300+ incoming and never hits 5tds after the brane. Actually I see 4 and it drops to 3 then I will start processing it through the d.i which is probably a 10min flush. But you should be way lower .

I would definitely check that you have the correct flow restrictor, and the membrane is the correct size and seated well.

I have 150g per day unit but it uses 2×75gpd filters are you sure you have the correct membrane? Something is going on?

This. I run about 10 post membrane but I use a single 150gpd membrane. Spectrapure is one I use. The DOW filmtec is the gold standard if you dont wanna worry about if its any good. Id prolly avoid amazon for those as some counterfeit ones got into the chain.

Lbrdsoxfan · Mar 23, 2023

thatmanMIKEson said:
I dont pack it with something just tap it on the table as you put in a little at a time, tap tap tap

I do much the same, I usually add some rodi as I fill it, tends to help compress the beads ime.

Randy Holmes-Farley · Mar 23, 2023

I don't know what it might be, but the ambient air CO2 is not an issue unless the DI resin was left open to it.

CO2 in the water can deplete a di pretty fast.

What brand DI resin?

Are you on well water?

o2manyfish · Mar 23, 2023

In the original post you stated that after a week the TDS was 40 after 'running'. How long are you letting the system run before testing/collecting the water.

I found that the TDS of the water sitting in the RO/DI system when not in use rose pretty high. I built a timer that dumps the first 10mins of production water after the unit has been off.

So when you say testing after 'running' is that 2min, 5 min, 10min, 30min.... You should see the TDS Drop the longer the unit runs.

Dave B

Randy Holmes-Farley · Mar 23, 2023

thatmanMIKEson said:
no r.o membrane should have that bad of a rejection rate. I have over 200-300+ incoming and never hits 5tds after the brane. Actually I see 4 and it drops to 3 then I will start processing it through the d.i which is probably a 10min flush. But you should be way lower .

I had two different systems from Spectrapure that did. About 100 ppm TDS into the membrane and about 9 ppm TDS out.

thatmanMIKEson · Mar 23, 2023

Lbrdsoxfan said:
This. I run about 10 post membrane but I use a single 150gpd membrane. Spectrapure is one I use. The DOW filmtec is the gold standard if you dont wanna worry about if its any good. Id prolly avoid amazon for those as some counterfeit ones got into the chain.

Absolutely!

thatmanMIKEson · Mar 23, 2023

Randy Holmes-Farley said:
I had two different systems from Spectrapure that did. About 100 ppm TDS into the membrane and about 9 ppm TDS out.

Well that's if every tds meter is accuratly reading any way, but it should be a lot closer to the manufacturer specifications.

Otherwise what's going on why would they even give a rejection rate if it's just a wild random number, I'd say you had an issue to? Idk what's the answer?

killer2001 · Mar 23, 2023

I flush my membrane for 1 minute before sending it through the DI resin. My tap water is about 160 ppm TDS, before it reaches the DI resin its about 5 to 6 ppm TDS then after DI resin 0 ppm TDS. Typically when I see > 10 ppm TDS before the DI resin I will replace a sediment filter and carbon block. Seems to be working for me so far.

Randy Holmes-Farley · Mar 23, 2023

thatmanMIKEson said:
Well that's if every tds meter is accuratly reading any way, but it should be a lot closer to the manufacturer specifications.

Otherwise what's going on why would they even give a rejection rate if it's just a wild random number, I'd say you had an issue to? Idk what's the answer?

Maybe, but there are several reasons to not get to 98%+ rejection, and I believe these systems at the time were not claiming as high as the 96% membranes spectrapure sells today.

1. Different membranes have different rejection rates for any given chemical.

2. Different chemicals in the water will give different rejection rates.

Miami Reef · Mar 23, 2023

Randy Holmes-Farley said:
What brand DI resin?

BRS mixed bed. I buy the single use packs and I fold the original packaging and store the unused into a ziplock bag. Then I use whatever remains and fill the rest of the cartridge with new resin.

I noticed the older resin is more dry and the individual granules don’t stick together.

Randy Holmes-Farley said:
Are you on well water?

I live in the city. I’m pretty sure I don’t live on well water.

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