The DM-1 Dual Inline TDS Meter from HM Digital is one of the most important reverse osmosis accessories. This tool monitors the TDS of your reverse osmosis system in two places and lets you know exactly how the system is performing.
BRS suggests: installing the dual TDS meter post membrane and post DI stage. These two readings will notify you when it's time to change the RO membrane and DI resin. This unit features a digital display and comes with two 1/4" John Guest Quick Connect Tee's. As with all HM-Digital products, the DM-1 comes factory calibrated.
Two meters failed out of the box By Alvo on 4/10/2017Alvo wouldn't recommend this product to a friendI ordered RODI system with this meter- out of the box and a second meter failed to register.
Ok By Jason on 1/14/2017Jason would recommend this product to a friendWorks ok, but need to be careful to avoid damage. Seems to be accuarate.
A must By John from Dallas on 3/16/2016John from Dallas would recommend this product to a friendThe unit is simple, accurate, easy to install and a must for your RODI system. I'm thinking about adding another Deionizer and wish I had bought the triple unit for a few dollars more, but still an excellent buy.
Don't waste money on replacement filters By Joshua on 3/9/2016Joshua would recommend this product to a friendBasically this will allow you to take the guessing game out of when to replace your RODI filters. This is super easy to install and easy to use. To be fair I have no way to tell if this is accurate since I am completely relying on the TDS meter on this unit. But I did use this right after I changed all my RODI filters and I had a TDS of 320 going in and a TDS of 1 coming out. I use a 4 stage/75gpd RODI unit.
Easy to install By Mike on 2/5/2016Mike would recommend this product to a friendNo more guessing when it's time to change filters, resin or membrane.
Always trusted a local shop with a stick meter, that was a mistake I'll never make again. This meter is accurate and easy to install. Great price too. Wish I had ordered this a long time ago.
Accurate Reading! By Tony on 1/13/2016Tony would recommend this product to a friendThis is the most accurate meter I have owned!
Can't go without By Anthony on 12/21/2015Anthony would recommend this product to a friendWorks as advertised. Good to know when you're producing quality water!
Worth every penny By Corey on 10/21/2015Corey would recommend this product to a friendIts too good of a price to pass on if you dont have something to read tds. Highly recommend it. Works like a charm
Great Product By Randy on 7/19/2015Randy would recommend this product to a friendThis works as advertised. Does exactly what I need it to do. Purchased this back in Dec 2014, and its still working perfectly.
Very Nice Product By Eagle1 on 6/28/2015Eagle1 would recommend this product to a friendWorks well, I haven't had an issue with it yet, I have the 1 in and 1 out, I disconnected the out due to misplacement of the inlet valve not in line with my unit, I had a small leak, as long as the out is working I am good.
Works perfectly By Craig on 6/26/2015Craig would recommend this product to a friendWorks perfectly, letting me know my TDS before and after my DI resin. I bypass the DI resin until my TDS is below 10 and then monitor both sides after that. Recommended.
Nice Unit By Eagle1 on 6/11/2015Eagle1 would recommend this product to a friendInstalled this dual meter on my RO/DI unit today, I had to make up some different connections to get back to the supplied "T" on the in side but wasn't too much of a hassle, meter is correct on what my water is 120 going in and 0 coming out.
Ask a question
It sure is. It uses a pair of button batteries that can be replaced fairly easily.
These meters read from 0 ppm in increments of 1 ppm to 999 ppm. (9990 with calculation) This will not go be lower than 1 ppm measurements. Feel free to let us know if you have any further questions!
My question is what is the best way to test ( Deionized Water) the meter and calibrate it if necessary?
We don;t recommend calibrating the units as we have not found them to be out of calibration since we have been using them. The calibration steps would also need to occur in a laboratory environment. If your TDS coming out of the membrane is in the 100's there is most likely an issue with the membrane, which possibly needs to be replaced or a bacterial bloom in the housing.
This TDS meter uses an LR44G Battery.
The TDS meters on the units do not need replacement. In many cases they will last the life of the unit. It very well be that CO2 or other elements are reducing the DI resin faster than any TDS. Feel free to let us know if you have any further questions!