Tips for zero TDS water

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I finally went out and got myself a com-100 tds meter. Up till now I have been relying on two inline ones in various sages of the filter set up. According to the inline after I run it for about 3 gallons my ro is about 1-4. after an hour or so i am down to 1. The com-100 reads it at 2.5. DI output on the inline is zero and about .2-.7 on the com in the KCi setting, which is another question I have. Not sure which of the four ppm setting is the most appropriate for this application.

My questions is what can I do to get down to a 0.0 reading on the DI out? I'd like to see zero if it's possible. I saw a thread a little while ago where someone mentioned clipping the restrictor to the appropriate length but could not find any more out about it. My system is a dual 75 gpd membrane with a dual DI and a booster pump as well.

 

[AZDesertRat]

What is your tap water TDS and RO only TDS? What is you water pressure at the membrane and your water temperature? What is your exact measured waste ratio? Do you make water in nice long filter runs or short spurts? Membranes need to be flushed and its the waste ratio while it is running that does so.

What sediment, carbon block and DI filters are you using? What RO membrane do you have and how old is it? The sediment and carbon have very little to absolutely nothing to do with final TDS but they do the important job of protecting the expensive RO membrane which does 90-98% of the work and acts as pretreatment for the DI. If the membrane is not in good condition and working at its 96-98% rejection rate then DI does not stand a chance.

How old is the resin and has it stayed wetted or moist at all times? Do you use the same resin in both DI's? If so you can install a tee and ball valve between the two canisters so you can test the DI's individually. In that way, when you start to see any TDS in the first DI, you rotate the second cartridge into the first canister and install a new cartridge in the second spot to get maximum life out of it. Myself I use the MaxCap/SilicaBuster combination but still measure the TDS from each individually. I get 3-4 MaxCap replacements before replacing the first SilicaBuster and get over 1000 gallons per MaxCap and 3000-4000 gallons per SilicaBuster before I see any TDS at all and thats in Phoenix with a tap TDS arond 600.

Congratulations on the COM-100! Its the meter I use and trust myself and I use the KCl setting.

 

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Thanks so much for the response As soon as I get home ill get all the answers for you


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Ok so here is some info for you

first off here is a pic of the system.

The tds of the tap water at 52 degrees is 347

The tds of the RO at 52, after about an hour is 2.5 on the com

In one minute I got about 410 ML from the di and the waste. Id say it's very close to 1:1

Both membranes are filmtec 75's and are less than a year old.

I run .5 micron sediment filter before the booster then have a spectra pure pleated zetta zorb, then a matrix cto and a cto plus. from there it goes to a max cap di then two more Spectrapur di cartridges

My first stage sediment is orange in about two weeks so I go through them pretty quickly. It's more of a means to preserve the pump and the more expensive pleated cartridge .

With the pump on my pressure needle is buried. with out the pump I have about 82


I asked my municipal water guy what they use to disinfect and he said chlorine and chlorine gas. My water normally smells like chlorine but about once a month for a few days I can really smell strong chlorine/chemicals and it appears yellow sometimes even so I figured running the two carbons would not hurt. I go through one maxcap every month or so and the two DIs get changed as soon as the first one reads 1. I swap them and put the new one second in line. Just like you said. I do have tds meters on both outputs and one on the maxcap output as well. I am not really sure how much water I make durring that time but it's probably near 1000 gal give or take.

The resin is alway wet.


For top off I have a 40 breeder that i fill about twice maybe three times a week. I try to incorporate filling it into my water change schedule so I can fill up my SW tub as well. so I either make about 38 or 100+ gallons at a time. No short spurts at all and I like to let the Di output flush into a bucket till it reads 0 (on my inlines at least). Once I am there i close the valve and fill up the reservoirs. I flush the membane at least once durring this ime for a few minutes sometimes three or four times. The longer it runs the more times I end up flushing it.

I hope that gives you some more to work with and if I left anything out please let me know.

Thanks again,


Adam

 

[AZDesertRat]

Do you have a water softener? Do you have any idea what your water hardness and pH are?
You say you get orange on the first filter, do you know the iron content of your water?
Do you know if your water utility feeds phosphates as a form of corrosion control in the distribution system?

I would highly recommend getting your waste ratio up to at least 3:1, those who recommend dual membranes and booster pumps as a way to reduce the waste ratio are uninformed and your membrane(s) will fail prematurely. Yes, you can reduce the waste ratio to between 2:1 and 3:1 IF you have softened water and low to normal TDS, 250 or less. You will notice those who have been researching and building RO systems for decades do not recommend cutting the waste ratio on their dual membrane systems, the second membrane receives the concentrated waste from the first and its even more important to keep it well flushed. The only way you can safely reduce the waste ratio is if you have softened water, low TDS or use stored DI water to flush the membrane such as Spectrapures MaxCap UHE does. They are now selling autoflush low waste systems but when you read the recommendations they say soft water is very important and they ship with 2:1 AND 3:1 flow restrictors depending on your water quality, still much higher than 1:1.

Throw the flush kit out the window, its only giving you a warm fuzzy feeling and really doing nothing to help the membrane or your water quality. It does not increase the velocity or the volume enough to do any good and nothing short of chemical treatments or DI water will help the membrane cleanse itself.

 

[carlosh080]

Just like members have said a fluah helps. My tds was going up the first time i set it up after a few weeks. Once i flushed it, tds wwnt back to zero. Now i flush every two or three days

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[AZDesertRat]

They are worthless.There is no proven documented proof they do anything besides lighten your wallet.

It cannot change the finished water TDS as it is on the waste circuit not the treated water side of the RO membrane. If you want to flush something that will help your final TDS then install a DI bypass valve and flush the TDS creep water which IS on the treated wate rside of the membrane to the drain, that actually serves a purpose and makes your DI last longer.

 

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Thanks again for the informed response. I really appreciate it . I'll try to answer all of your questions again.

I do not have a softener.


On a different occasion I had someone from the town office tell me that they do use phosphates in the water so yes to that. I do not know the iron content though. the ph of the cold right out of the tap was 8.1


I have to admit I never really understood what the membrane flushing accomplished but if you look at the pic of my set up, the tube spun up looped through the housing is my pre di flush. I open this till my tds is down to 3 or 4 then let it run to the di, but I also discard the first gallon or so of di till it gets down to 0( or what I thought was 0) turns out to be anywhere from .8-.2 on the com 100.

SO I understand that I need to increase the ratio but I do not know how to go about doing that. A different restrictor? Should get rid of the second membrane altogether even?

I will loose the flush then for sure. What you said makes perfect sense.

Thanks again for the input,

Adam

 

[AZDesertRat]

Phosphates may be at least part of your problem. RO is not particularly effective at removing them and since they are weakly ionized they do not register well on a TDS meter. Good DI resin such as the SilicaBuster with long slow contact time is the best thing you can do for them.

Yes you need a different flow restrictor trimmed for your dual membranes.

One thing that may help is by getting rid of the second membrane you lower the GPD and slow the velocity through the DI resin so will have longer contact time with your DI resin.

 

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So this may me a tad hasty but I just went and got a new 75 gpd membrane and appropriate restrictor. Just figured i'd start new. I'll loose the 2nd membrane for sure.


The new restrictor is the larger white inline type, not the capillary one. I am just assuming that when paired with the 75 gpd membrane i should be getting closer to 4:1 then?


Just out of curiosity would you happen to know what other sorts of things could be in the water that ro might not get out but would also not read well on a tds meter?

I checked my reservoir yesterday after it was full and it read 0.3 on the com. Just wondering what types of stuff that .3 tds could be and what else may be in there but not showing up on the meter.

I have been pretty leery of the water quality here for a good while. I did some digging but could not come up with much. I had someone look at my water report and while they said it was pretty good they also said it was one of the flimsiest ones they had ever seen as far as what info was actually in there. Ultimately I just want to make sure I can get whatever is in there, out effectively.

Thanks again,

 

[AZDesertRat]

Other weakly ionized substances are nitrates or all forms of ammonia really and silicates. There are many others but these three including phosphates are the ones we would worry about in the reef hobby.

Measure your waste ratio using the fixed restrictor, if it is a 750 mL or 800 mL it should get you close to 4:1 but its hit and miss as not everyones conditions are the same. I hate the things myself.

My advice to you is to make a friend at your local water utility or treatment plant. Having worked in municipal treatment plants and water production facilities most of my so far 38 year career I have befriended many aquarists who called the City offices and asked for water information. Most people working for the City knew of my hobby since I kept saltwater tanks in my office and even maintained one of my own in the lobby and waiting area for the public to view. I even had a nano on my clerks desk!
Someone in the know can give much more information than is contained in the annual Consumer Confidence Report required by the EPA.

 

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Ok thanks again for the advice. Really appreciate it. I got the new membrane and 600 restrictor all up and running. I have very close to 3:1 as it is. I still have the capillary one. Would it be wise to mess with it and try to get closer to 4:1. I am assuming that to do this I would need to clip the length till I get it where I want?

After about 20 minutes I started taking tds readings and out of the final di the best I got was teetering between 0.0 and 0.1 ultimately settling on 0.1. I shut off the booster pump as well to increase DI contact time and still bounced between 0.1 and 0.0

Ro out tds is 5 on the inline

I live in a pretty small town and the water plant is also small. The guy who seems to be in charge is also in charge of a lot of other things. I have talked to him quite a few times and never got much out of him. I may not have been asking the right questions either.

But hey thanks again for all your help.

 

[AZDesertRat]

With your tap water TDS around 350 I would try to get the waste ratio closer to 4:1, if it were say 200 or so you could get by with 3:1.
Any of the Spectrapure owners manuals have the complete capillary tube instructions in them, most are on around page 8 of the manual.

 

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So i am getting closer. I had an old 800 restrictor that I never used so i put it on there. I am just about at 4:1 now and tds are edging at 0.0 It still bounces a little but stays on 0.0 longer.

am I about as far as I can go with this? I did get one of those cheapie strip water test kits and the only thing that read exceedingly high was the hardness. Test result was "very hard" iron was low

 

[AZDesertRat]

Looks like you are about there.

 

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Ok then one last question. Now that I am putting much more waste water down the drain. Do you know anything about the zero waste kits? They run the out to the hot water line. Something like that. You would cringe if I told you what I spend a month on h2o


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[AZDesertRat]

They only work for low 15-20 GPD drinking water systems and even then are not a good idea. They route the waste back to your hot water which will speed up the failure of the sacrificial anode inside the heater and require replacement of the tank sooner. I soften my water, whey would I want to put the concentrated brine back in the water to raise the hardness and TDS back up? Thsy sound good but don't really work that well.

My combined water/sewer and other City services bill is $100 in winter months when the rates are low and around $180-$200 in summer months but really only a small portion of that is actual wate rand sewer charges. Our water is between $2.00 and $3.50 per thousand gallons and sewer charges are based on the water usage and come out to a little more than the water. I make around 100 gallons of RO/DI a month so at the normal 4:1 waste ratio I would actually use 500 gallons a month for RO/DI. Worst case my RO/DI costs me about $3-$4 a month on my bill.

In truth I have a Spectrapure MaxCap UHE RO/DI system running at slightly less than 1:1 waste ratio so my water and sewer charges are less than that but I was figuring using a normal 4:1 system.

 

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Thats what I thought. I did not really get it. is that 100 and 180-200 a monthly cost?

Thanks a lot for all your help on this one. If you ever want any acro frags let me know

 

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I have another quick quandary. I just replaced my maxcap today and flushed it till about .01-.02 Tds. After I hooked it back up, coming out of the final di I could not break .04 on the com. Of course it's zero on the inline which what I had been going by till I got the com Any idea what my be going on here

Tds in to the maxcap is 5-7


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So for what it's worth I just tested the out of the maxcap again after running a couple hours. And it's zero. Coming out the final di stage is between .4-.5. I am a little confused by this.

It would seem the di is adding Tds?


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