RO/DI Spectrapure TDS question

[thasby]

I have a Spectrapure MaxCap 90 5 stage unit with dual DI's and dual TDS meters. left meter reads 434 coming in and 14 out. which is about 97% rejection. My problem is on the DI side it reads 0 on "in" and 3 on the "out" . I don't in my head think this is possible. Any input? both di cartridges were refilled about 2 months ago. I have maybe made 80 gallons since then.

 

[RedReefer]

Are you sure you don't have the in and out backwards on the tds meter. I know on my tds meter you can push a button to switch the in and out around. It should ne opposite of what you posted.

 

[AZDesertRat]

Try swapping the IN and OUT probes to see if the readinsg stay the same or travel with the probe.
Make sure the probes are rotated in the correct direction also, it makes a difference.

I have a MaxCap with the two meters also but honestly I never even turn the inlines on, I always use a good handheld for accuracy since the inlinesa re not temperature compensated and lack the accuracy of a handheld, especially on the low end readings.

When you replaced your DI, why did you do both and what resins did you use? You should be able to swap three or more MaxCap cartridges before you have to replace your first SilicaBuster cartridge. Also did you properly pack the replacements if you used bulk resin? How old was the resin you used and was it shipped, packaged and stored properly? Resin has a relatively short shelf life, espcially if it has been opened or not stored correctly.

 

[thasby]

Unit is 1 year old. Use to read 0 on the out side. I have never removed the probes to get them backwards. I replaced the first di cartridge and then the second one a month later as it never reached 0 going out. I use BRS packed resin. Just bought it and installed it right away. Not sure what you mean by properly packing cartridges. All fit in with sponge on top. I will switch probes and post what happens.

 

[AZDesertRat]

If you are using BRS reswin in a Spectrapure system you are missing the whole point of having a better designed system, the resins are night and day different. The MaxCap system is designed to use MaxCap resin in the first cartridge and SilicaBuster in the second cartridge and no other resin works the same or even near it. Its like buying a Ferrari and putting a Yugo engine in it, it functions but thats about it.

With two plain old mixed bed resins you still need to monitor both DI's separately, when the first starts showing any TDS, you remove it and place the cartridge out of the second into the first position and place a fresh cartridge in the second spot. Still nowhere near a MaxCap system but it should make the DI last a little longer providing you are using fresh resin which has not been opened or if it has it was resealed using a seal a meal vacuum sealer and stored in the refrigerator. Resin lasts about 6 months tops if unopened and stored in the frig and less if not. Never buy more than you can use in maybe 3 months time and alwasy reseal and store properly or you wasted your money.

I would use up what you have and go back to the real deal with the MaxCap/SilicaBuster combination if it were me, it will last longer, work better and actually cost you much less even though the initial cost may be more since it will last over 3 times longer. Years of research and development went into that resin combination and its proven. When I switched from bulk resin, no matter where I bought it to the MaxCap system my resin went from 150 gallons per refill to 830 measured gallons on the first MaxCap cartridge and over 1000 gallons ever since and 3000+ on the SilicaBuster with no other changes. There really is a difference!

 

[thasby]

Thanks for the good advice. I will go back to the SpectraPure cartridges. Just trying to make the wife happier with lower costs, but like you said in the end it is no cheaper. I had just let the sediment and carbon go too long a while ago and had to replace too many at once.

 

[AZDesertRat]

The sediment and carbon block have very little to absolutely nothing at all to do with TDS. They protect the RO membrane from TSS or suspended particles, large floating stuff and chlorine, not TDS or dissolved solids. You change the sediment and carbon every 6 months or if you take a little time and monitor your headloss using the pressure gauge and an inexpensive low range chlorine test kit to monitor the carbon condition you can push that out to 12-18 months. TDS does not tell you anything about their condition or when to change them. TDS only applies to the RO membrane and the DI resin. TDS is in the 0.0001 micron size range, sediment and carbon filters are in the 0.5 to 10.0 micron ranges, many hundreds or thousands of times larger so do nothing for TDS. It is best to use the Spectrapure replacements if you want to get 5-7 years or longer out of the RO membrane, I have even seen some go 10 years with good maintenance and quality replacements. A 5 or 10 micron nominal rated filter others sell is about as effective as a screen door compared to a 0.5 micron absolute rated filter.

 

[thasby]

Thanks for the very useful info. I ordered both new DI cartridges from Spectrapure yesterday. The sediment and cb filters are GE brand 0.5 micron. One last question I have is that my source water comes from my US Waters brand water softener. This softener has a carbon section in the head that water is suppose to go through that. Is this doing me any good or just taxing my softener and salt use? My TDS is the same from the softener or directly from city water source.

 

[AZDesertRat]

Make sure the sediment filter is absolute rated and not just nominal rated or what some call a depth filter. There is a huge difference in the amount of particulates and colloidal materials it traps versus allowing it to pass through and lodge in the pores of the carbon block, not all filters are the same.
I am not sure about the carbon in your softener. It is probably still of value since not all softened water is going through the RO/DI and its carbon block.
Softeners do not lower TDS, in fact they often raise the TDS. They remove or lower the calcium and magnesium content but exchange it for sodium and its not always a 1:1 exchange so the TDS can go up but the sodium is easier for the RO membrane to process so is a good thing.