I have found the pvc mini-float valves at usplastic.com to work well.

The inline TDS meter should just fit somewhere in the pure water line between the system and the tank.

Doesn't one of the tubes go on the part before water goes into RO system (the raw water) and the other one goes into the pure water (after the RO system) line before it hits the tank?

---------- Post added at 11:09 AM ---------- Previous post was at 11:07 AM ----------

It's an HM Digital DM-1 In-Line Dual TDS Monitor, 0-9990 ppm Range, +/- 2% Readout Accuracy

Right you are - but still easy to install.

Cut two lines, plug the cut ends into the sensors and away you go.

Excellent! Success will surely be reported mañana!

Most monitors I’ve seen test the pure water only you simply got an upgraded one.

I don’t know the membrane you may have, but your pure water TDS shouldn’t be more than a few percent of the incoming TDS.

Well TaDah!!!

All stuff now successfully installed! I had to water, so haven't checked to make sure the float valve shuts off. Was too nervous to keep it running all night after last episode. I'll turn on again this morning, and we'll see how it goes.

So TDS on inflow side was coming in at 335 and later in day at 376. I presume it fluctuates a bit. The pure water side is at 5. So that's a tad more than 1% if I did the math correctly (5/375 right?). And that also means no changing of the cartridges yet, right? Wouldn't it be nice if the other cartridges had that color-changing stuff like the DI cartridge so one just knows when to change?

Gracias to all who stuck with me to get this done and advice given. :bowing It takes a village here in WaterWitchin land to get stuff installed. :biggrin:

There are filter monitors available, like the HM Digital FM-2.

However, those self-contained filter cartridges are typically good for 12 months or 2500 gallons (at least the ones I sell are), and the membranes for 2 years or 12,000 gallons.

I simply put them on my Outlook calendar, and if I see the TDS rise or the output fall, I know I need to do it sooner.

Where’s the output part on the system? And yes on the math? The TDS part at 1%?

5/375 is 1.3%, yes. That mean 98.7% of the dissolved solids are in the flush water, and now that you’re at a 1:2 pure:flush ratio, that flush water has a TDS of about 560.

I’m not certain what you’re asking with that first question, but the “system output” can be the pure water line, the flush water line, or both, depending upon what you happen to be referring to.

I thought maybe there was something actually metering it. Evidently just eyeballing the output from pure water, or tracking how long it takes to fill a gallon jug then. I think I'll stick with the TDS meter.