Ro water Tds what's the magic number?

[BrentH]

Does everyone change out there di etc when there output is anything besides 0? What's the highest it can go ? I've been keeping at 0 but it went to 1 Tds quickly this time for me

[bertoni]

What TDS level is safe depends on exactly what's getting past the filter. We generally don't know what's in the water, and when the DI resin is exhausted, it can release some things we don't like in our tanks:

http://reefkeeping.com/issues/2005-05/rhf/index.htm#7

[jay13]

mine runs between 3 and 5. to some that is ridiculous to others (like me) it is fine. guy down the road running well water thru his is 40+ with no problems.

[disc1]

You can't use TDS that way. TDS can tell you how well your filter is working, if you have more than zero then the DI resin isn't doing its job.

But TDS can't tell you anything about whether or not the water is OK to use in your tank because it doesn't tell you what is in it.

[tmz]

FWIW, I always keep post di tds at zero. It is likely more harmful than post membrane tds. I use two canisters of resin with a tds meter in between them. When the output of the first goes past zero the resin is changed and it's rotated to second in line . This avoids guesswork on when to change resin.

[BrentH]

I' feel most comfortable when it's at 0 I actually have a whole house carbon block filter and soft water that I think May prolong the ro filters and di 5 seems like a lot I'm just curious of what others do or how they judge when it's time to service or unit

[AcroporAddict]

My post DI TDS is always 0. We are lucky in my area of the country in that our tap water has a TDS of 35-38 usually, so RO membranes and DI resin last a long time. I change my DI resin out once a year, and I make a lot of RODI.

Downside to my area is we have the highest water rates in the country, due to Atlanta having to replace it's aging sewer and water pipe infrastructure. Only thing that helps me is I am on a septic system, so I don't pay sewer charges.

[BrentH]

In so call Tds out of tap is like 390 :0

[BrentH]

I actually have 4 di on my ro setup can u have to much di with meter after each 2 di cartridges does di do anything negatively to the water? That may sound like a weird question ?

[Randy Holmes-Farley]

No, there is no such thing as too much DI.

IMO, the only "magic" number is 0 if measured in line. Anything else might possibly be too much of something.

FWIW, when a DI depletes, there may be things in the DI effluent that are substantially higher than in the source water. Ammonia and silicate, for example, since they are only weakly held and are easily displaced by incoming sodium or chloride.

I accidentally let a DI deplete once, and my limewater (kalkwasser) stank of ammonia.

[AcroporAddict]

To the OP: there are color changing DI resins you can buy that help a lot in determining when to change them out. I use the BRS version, but still use an inline pre and post TDS meter. Last time I did my annual DI resin changeout, my resin was about 3/5 exhausted, and the resin showed a very clear delineation between the tan colored exhausted resin and the bluish remainder.

[tmz]

With tap water tds at 250tds , I go 4 plus months before there is any tds reading out of the first canister in line . I change the carbon filters once every 6 months , the sediment filter when it's dirty usually every 6 weeks and the membrane every few years.

[AcroporAddict]

In so call Tds out of tap is like 390 :0
At tap of 390, you are gonna go thru a pretty good bit of DI resin. I think I'd be buying BRS bulk quantities, if you don't already.

[BrentH]

I actually just started using refillable di cartridges there great!! I was trying to go strictly spectrapure ro refills but hard on the wallet bad that route!

[Reefvet]

In so call Tds out of tap is like 390 :0

390, pfff.

Santa Barbara water is 485. You can practically chew the stuff :lol:

[AcroporAddict]

390, pfff.

Santa Barbara water is 485. You can practically chew the stuff :lol:

Must be fun washing cars with that stuff.

[brad_G]

Well I would like to know what everyone's tap, pre ro, and pre di TDs are? Last time I checked I was around 250 after the filters and seems like my tap is very close to that. I had been 15-20 after ro but I finally got a new film tec membrane and dropped it to 6-8.

[Randy Holmes-Farley]

t time I checked I was around 250 after the filters and seems like my tap is very close to that.

FWIW, the carbon and sediment filters won't lower the measured TDS. :)

My tap is a lot lower than yours (about 95 ppm) and my post RO water is about 9 ppm TDS.

[tmz]

With 250 tds tap water , pre di /post membrane tds is usually around 10 to 13 for me. I use a 75 gallon per day membrane with a flow restrictor sized accordingly,Pressure is around 50psi.

[bambam918]

Right now in AZ my TDS is at 650. Have had my DI for over a year. The 4 stage really helps prolongs the DI life

[hkgar]

Not trying to hijack, but I see references to using 2 DI cartridges and rotating the first to position 2 when it is no longer producing 0. Somehow this is supposed to reduce DI resin usage.

How?

[tmz]

Only by avoiding premature changes . Don't need the color changing dye this way etiher. The first catridge in line is exhuasted when it reads more than zero;the second maintains zero until you change the first and rotate it. So, you know you are changing exhausted resin without anything above zero coming all the way through. The second course of di can also knock down any sub 1ppm tds getting to it ;some tds can be harmful at even less than 1pmm which won't show up on a tds meter.

[Randy Holmes-Farley]

I do this with two cartridges, swapping the last one into the first slot when, as Tom mentions, the TDS begins to rise after the first DI. This allows one to completely use a DI cartridge without getting water with >0 ppm TDS in the effluent. :)

[hkgar]

I do this with two cartridges, swapping the last one into the first slot when, as Tom mentions, the TDS begins to rise after the first DI. This allows one to completely use a DI cartridge without getting water with >0 ppm TDS in the effluent. :)

Thank Randy and Tom. I now understand and it makes sense. I am ordering a second DI canister to set up my system that way.

[tmz]

You are welcome , I think you'll like it;I do.