Does anyone have a DI meter built into their RO/DI?

[Aquattro]

IMO, if it's included, fine, but I wouldn't pay extra for it. Any meter will need calibration at some point. With properly maintained pre filters, flushing your RO membrane and running DI resin that indicates exhaustion with a color change, you'd be good for years. If the TDS meter is going to give you peace of mind, fine, but it's money you could put towards something else.

[craigwmiller]

I recently added a Dual Inline TDS meter to my system (previously using just a hand-held). I placed the two points after the RO membrane, and then after the DI.

The pre-filters don't really do much for TDS (which is measurement of much much smaller particles), leaving the membrane and DI resin doing the brunt of the work... Since DI resin is costly, knowing how efficient my RO membrane is operating is very important! I now can do a more serious flush of the membrane when the TDS post-RO is >5 TDS... and with the dual meter, I can quickly (seconds) have peace of mind that the post-DI water is still 0 TDS.


Using a hand-held checker getting measurements from the post-RO/pre-DI water is still totally possible - though somewhat tricky... It would take a Tee, check valve, and manual shutoff valve, letting you divert some water from the post-RO/pre-DI stream... you would need the check valve between the Tee and the DI though to ensure you don't get back-flush water from the DI into your Tee causing your reading to be skewed.

[gregzz4]

I should have elaborated on my setup
I have both a single and a dual meter
I measure supply water, post RO and post DI
FYI, I also have pressure guages on my supply and pre-RO to monitor the filters. You could say I'm a bit OCD

For the OP, as Brad stated, if it's included and is comparable to what I linked above, go for it

I only mentioned what I use as I like to keep an eye on most stages of my system

[Myka]

I like an inline TDS meter in one place - between the RO membrane and the DI resin so that I know how much TDS is going to the DI. This is a luxury though, and not needed. I like to use a handheld meter for product water. Make sure that any TDS meter that you buy is either self-calibrating when you dip it in calibration solution or it has manual calibration. All TDS meters are "factory calibrated" but do not buy a TDS meter that you can't calibrate afterwards because the calibration will wander off.

IF you buy a dual TDS meter, spend the extra few bucks to get the HM Digital DM2 as it has dual calibration where the DM1 has only one calibration screw for both probes which often do not read the same, so it is impossible to calibrate both probes properly. Or make sure whichever brand it is that if it has dual probes it also has dual calibration. The ones Greg linked to above are both the DM1.

I have fond that I can't rely solely on the color of color changing DI resin because I found the outside of the DI resin would all change color and I would dump it out to find the core of the DI resin still had plenty of color! So now when the color on the outside is all changed that's my red flag and I start testing product water until it shows 1 ppm, and then I change the DI resin. In my case, the DI resin often last another 4 months or so after the outside portion has changed color.

What is the TDS of your tap water? Phosphate level? Chlorine/chloramines?

[gregzz4]

Originally Posted by Myka

HM Digital DM2 as it has dual calibration where the DM1 has only one calibration screw for both probes which often do not read the same

Mindy, have you some more info on this ?
I'd like to know if I'm looking forward to some kind of failure
I currently own the DM-1 and the SM-1

[Myka]

What info do you want? Google for owner's manual for the DM2 to compare. Have you tried calibrating yours yet? Put both probes into the same glass of tap water and see if they read the same. If they do you're lucky (for now), if they don't read the same then there is nothing you can do to get them to read the same. Then you need to set the lower reading one to the calibration solution (usually 342 ppm), and if the second one then reads 3 ppm higher you just have to remember that 3 ppm on the second one means "0". That's about all you can do.

[gregzz4]

I wasn't expecting to hear issues

I've never had to cal mine since I bought them
Looks like I'll have some fun to deal with in the near future ...

Oh, and thanks for the info

[gregzz4]

Thanks again Mindy for the info
Every day there is something to learn about
Sucks that it's about my own gear

[Reef Pilot]

I have a dual TDS meter, one shows after RO and before DI, and the other shows after DI. When the RO tds starts to go up, it tells me it is time to flush the membrane. My final RO/DI water is normally 0 or 1. When it goes up it is time to change DI. When flow slows down, it is time to change the sediment and carbon filters.

[Myka]

Originally Posted by gregzz4

I've never had to cal mine since I bought them

What do you mean you've never had to? How long have you had the meter? You should calibrate every 3-6 months.