Ro Di TDS issues (1 Viewer)

[BrAin]

I'm having TDS issues with my Ro/Di system and looking for some help or guidance. I bought a system off the internet some time ago and added prefilters before the system because I thought this might help. I just replaced all filters, resin, and the membrane to fill the new tank. I've probably ran close to 400 gallons through the new filters and now I'm up to 212 TDS. Input from house is around 600 TDS. Lowest at start was 10 TDS output. All cartridges are from Bulk reef.
Currently running:
one: 5 micron sediment filter
Two: 1 micron sediment filters
One: 5 micron BRS chlorine and VOC carbon
One: 1 micron BRS chlorine and VOC
Two: 1 micron BRS universal carbon
75 gpd RO Dow Filmtec membrane
DI Resin

The universals are supposed to be good for chlorine and chloramine. I put in a flush bypass valve that I open fully on occasion but never let it run very long. Any advice? Thanks




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[FarmerTy]

Got a picture of your setup? I'm a little confused. So you added Prefilters before your Prefilters?

 

[BrAin]

I originally bought a system that had three cartridges on the bottom and then I added four inline before that. So all together there is 7 cartridges before the membrane.

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[paraletho]

600 on the incoming is awful high. What do you have to test TDS with?

 

[BrAin]

I use a hand held at home and I took a sample to our "lab" at work where we have two industrial hand held meters. Yes, it is awful city water.

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[dragon99]

The pre-filters will only do so much. You need to make sure you have the right pressure at your RO membrane (~90psi for best rejection). What's the TDS of the water coming out of the RO membrane? Is that the 10TDS? Do you have DI resin after your RO membrane?

 

[FarmerTy]

So basically two sediment filters, 3 carbon variants, then into membrane, then into DI?

What is your reading premembrane? Post membrane? Post DI?

600 TDS in should get you at least max of 30 TDS out with the minimum 95% rejection rate of most membranes. The 30 TDS can then be scrubbed by the DI resin to give you zero TDS.

 

[paraletho]

Make sure you are packing your resin cartridges evenly and fairly tight. I have seen water run through the center. So if you are using color changing resin it looks fine on the outside and used up in the center. Plus your not getting full use of your resin.

 

[paraletho]

Got to go Strontium test is through cooking. 15 minutes is a long wait before the last step.

 

[BrAin]

So basically two sediment filters, 3 carbon variants, then into membrane, then into DI?

What is your reading premembrane? Post membrane? Post DI?

600 TDS in should get you at least max of 30 TDS out with the minimum 95% rejection rate of most membranes. The 30 TDS can then be scrubbed by the DI resin to give you zero TDS.

There are three sediment and four carbon then the membrane then di resin.

I flushed the membrane for 15 minutes and saw an improvement in my numbers.
584 Before the membrane
142 after membrane
54 after DI

The resin isn't packed in so I'll do a better job when my new batch arrives. I also ordered pressure gauges to verify supply and differential across the system.

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[FarmerTy]

If you're not getting 0 TDS after DI, I would not use it in my tank honestly.

Something is definitely wrong, you're only getting a 76% rejection rate from your membrane... Should be at least 95%.

When you seated the membrane in the canister, did you take care not to touch it with your hands (bacterial fouling)? I usually wear gloves. Also, were you careful to not push it all the way in the canister? You're supposed to push it in enough to get the cap on it and use the process of tightening the cap to seat the membrane into the canister properly. If you just shoved it in as deep as it could go and then put the cap on, you've potentially allowed the system to partially bypass your membrane.

 

[BrAin]

No, never heard of the gloves and I think I pushed it in.

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[FarmerTy]

No, never heard of the gloves and I think I pushed it in.

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Can't do much about potential bacterial fouling now but perhaps pulling the membrane out a bit and retightening using the cap may help? You'll probably need to replace DI at this point as it is probably mostly spent having to deal with all the TDS coming straight out of the membrane.

 

[BrAin]

Double checked some stuff today and noticed the System was a 100 gpd and I replaced to membrane with a 75 gpd. I'm wondering if that has something to do with my problem.

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[FarmerTy]

I'm no RO/DI expert but the capacity is based on the membrane itself, hardware is all the same. So if you switched to a 75 gpd membrane, such as your case, then you'd had a 75 gpd capable RO/DI unit. The reason most go with the 75 gpd is because the lower gpd membrane is more efficient at filtering. If you went with the 100 gpd membrane, you'd get more water processed per hour but your efficiency would drop... Like 90% clean versus 95% clean with the 75 gpd membrane.

 

[FarmerTy]

If you got a 150 gpd unit, its basically two 75 gpd membranes stacked, which is what I'm running.

Detailed pictures of your setup and plumbing would be helpful in trying to diagnose your issue.

 

[Mark L.]

Did you make sure your flow restrictor was a 75 gpd since you put in a 75 gpd membrane? You mentioned adding a flush valve but didn't mention changing the flow restrictor. It has to match your membrane gpd.

Also you don't need that much chlorine removing carbon. I'd recommend the following....

5 micron sediment
5 micron workhorse carbon block
0.6 micron chlorine guzzler carbon block
100 gpd membrane (w/100 gpd flow restrictor)
DI Resin
DI Resin

That's really all you should need. Use one of the extra canisters as your second DI canister. I also highly highly recommend getting a 8800 booster pump. Install your booster pump between the chlorine guzzler and RO membrane. Your house pressure is fine for the sediment and carbon filters. You want to boost the pressure on the membrane.

Using this setup I get 1 TDS after my membrane and 0 TDS with spent DI Resin. I can run my DI Resin for weeks after it turns white before my TDS creeps up to 1. Like mentioned, you have to seat your membrane correctly and pack your DI Resin. Make sure you have the foam ring inside the DI cap. I pack my Resin so tight and fill the canisters to where I can't put the cap on. I literally put it in the counter and push the cap on as sim trying to twist it closed.

 

[Mark L.]

Also since you have so many canisters you could also do something like this...

5 micron sediment
1 micron sediment
0.5 micron workhorse carbon block
0.6 micron chlorine guzzler carbon block
100 gpd membrane (w/100 gpd flow restrictor)
DI Resin
DI Resin

I forgot to mention the reason for 2 DI canisters. It's so when the first is spent you remove it, move the second to the first spot and put a new one in the second spot. This helps so you don't get TDS creep once the single DI canister is spent.

 

[BrAin]

Ok, so I got the pressure gauges in today and I'm at 45 psi. I ordered a new membrane but I need a pump now.

I didn't change the flow restriction on the line. That part is still in service like normal. I added a bypass line and I open the valve fully on occasion to help clean out the system.

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[BrAin]

Thanks! I got the pump in and now showing 1 tds without making any changes. Next I'm going to remove the excess prefilters and run dual DI in series. I appreciate the help.

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