TDS Values

[joseayes]

Guys, I’m trying to get the standard TDS recommended values for a RODI system but I’ve a little trouble finding them elsewhere, would anyone help?
I’ve installed 4 TDS Sensors (that is 2 TDS DUAL SENSOR METER) along the system as this:
1st probe Sensor: after a prefilter, and booster pump, I know this one could be above 300 and below 500 TDS measuring quality water house.
2nd probe Sensor: after 2 pre filters, two carbon canisters, before the 2 membrane, I’m requiring this value, to determine the time that could be recommended to exchange the filters before the membrane.
3rd probe Sensor: I’ve placed this one after the two membrane and before the two DI canisters, obviously I’ve placed this one here to monitor water quality coming from membrane to determine when it could be time for a membrane swap. Intermediate value recommended need it here.
4th probe Sensor: this being the last one I know would recommend to be zero.

Any input will be appreciated. Thanks.

 

[chaples55]

TDS is a bad benchmark for determining the life left in a carbon block. The main thing you want the carbon block to remove is chlorine/chloramine, so to determine when the block is depleted you can take a water sample after the carbon blocks and test it for chlorine/chloramine. I have valves in my setup to make doing this easy:


As far as after the membrane goes, that will depend on the starting TDS, your operating pressure, and what kind of stuff is in the water. The lower the TDS going in, the lower it will be coming out. Higher pressure should also result in lower TDS coming out. Mine reads 0-1 TDS after the membrane but my tap water starts at just ~60 TDS and my system runs at 65psi. On Florida well water (starting ~400 TDS) and just tap pressure I was getting 15-20 TDS after the membrane.

 

[joseayes]

Thanks, I’ve installed the valves already to check and flush whenever need it. The 0-1tds is a good point of reference to ideally find what’s the quality water before sending it to the resin.
Pressure it’s handled with booster pump because it wouldn’t have enough and recommended to run through the whole system (two pre filters, two carbon, dual membranes and dual resin.
The values that I’ve requested are just for reference.

 

[jcook54]

I live in Dekalb county so your results may vary. I also have a whole house sediment filter that's 5 microns. I started with a 10 micron filter yarn filter and it got a LOT of crap out so I went to a 5 micron just to try it out. Man, I'm amazed at how much gunk is on the filter when I change it.

Water coming into my system - 40-45 TDS
-1 micron sediment filter
- I micron Carbon
- 5 micron carbon (for chloramines)
- RO membrane
Water exits the membrane 1 TDS
- DI resin
Water leaves DI resin at 0 TDS

I do not know what the TDS is before the 5 micron whole house sediment filter. I do know it gets filthy and the 1 micron sediment filter that's the first stage of my RODI unit doesn't seem to pick up all that much based on appearance. I change it out once a year and it'll have a bit of rust color to it but it's not bad. The carbon blocks are just for the chemicals and I assume they don't do much for TDS but I could be wrong. Finally, what comes out of the RO membrane is usually 1 or 0 and I replace it when it climbs up to 3-4 TDS. I don't know that I've ever truly exhausted DI resin. I run a mixed bed resin (cation & anion) and change it out once a year. Well, if I'm being honest it's a little longer than once a year but who's counting?

 

[Burritosanchito]

Your setup looks fine. Definitely check the TDS after your membrane and after your DI frequently. I have found that when the DI resin is exhausted, the TDS will actually go up significantly as the resin is releasing solids.