Features to look for in a TDS meter

With a TDS meter, are there particular product features one should look for or avoid?

I've recently started using more RO water from Walmart and would like to make sure I'm getting what I think I'm getting.

I don't want to buy a junk meter.

Any advice would be welcome.

I bought a junk meter off Amazon. Probably around 15 bucks. All I need it to tell me is if my RO is working properly. A reading of 7-15 is fine. If it said 200 I'd know the membrane failed. I don't know if it can do more than that but I couldn't see buying an expensive one.

I like HM Digital equipment. There are plenty of other brands, but don't go buying some off brand. These meters are fairly cheap, even from name brands. You should be able to get something reputable for $30 or less.

Thanks for the advice.

I'll look into thos HM products. I'm not familiar with them

I guess the Hach TDS is too much product for what I want.



$30 seems like a reasonable place to start looking.

Thanks again for the tips

How about this one from HM digital?

I just got a Chinese one off of e-bay for $5 from a US shipping address. In my well tap water it reads 298 PPM which is close to the 15 year old water report I had when the well was safety tested. Wal-Mart RO read 24 PPM, and distilled 8. So I think it's good enough for making sure the Wal-Mart Primo is up to snuff...

Fred

HM Digital is pretty much the standard in the aquarium industry, which is why I bought mine. Certain critters need low TDS conditions to thrive, so it's literally a matter of life or death for them. I use this one:

HM Digital TDS-4 Pocket Size TDS Tester Meter:
http://www.amazon.com/gp/product/B0002T6L5M/?tag=skimlinks_replacement-20

Coincidentally, I've seen water filter repair guys (Culligan) using the same meter, professionally. It's good to go.

Avoid the TDS EZ. It doesn't have automatic temperature compensation. You want that. The TDS-4 is also more accurate. +/- 2% vs +/- 3%.

KPBrews said:

HM Digital is pretty much the standard in the aquarium industry, which is why I bought mine. Certain critters need low TDS conditions to thrive. I use this one:

http://www.amazon.com/gp/product/B0002T6L5M/?tag=skimlinks_replacement-20

Coincidentally, I've seen water filter repair guys (Culligan) using the same meter, professionally. It's good to go.

Avoid the TDS EZ. It doesn't have automatic temperature compensation. You want that.

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Thanks for the info and pointers.

Inspired by your questions, I bought the TDS meter linked above by KPBrews and it came in today. 5 minutes ago I calibrated it in some 342 solution then tested my water, Houston's finest tap. 150 ppm. Lower than I was expecting, although I'm not entirely sure what typical municipal water should be at.

I bought this thing the same reason you did; to make sure Kroger isn't lying to me about their RO unit

TexasWine said:

I calibrated it in some 342 solution then tested my water, Houston's finest tap. 150 ppm. Lower than I was expecting, although I'm not entirely sure what typical municipal water should be at.

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What's 342 soln. ?

Gavin C said:

What's 342 soln. ?

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It's a calibration solution.

I think I'll go with that model also. Thanks @Texaswine

I wonder can a TDS meter be calibrated at 0 in distilled water. Not that it much matters as it's just a crude test

Is the Water RO yes/no

342 solution is one version of a TDS calibration solution. It was formulated to be more like a typical freshwater supply. The other option is a NaCl solution and it is composed of table salt and water...not exactly typical of a freshwater supply. Some TDS meters are required to be calibrated with one solution or the other. Some meters can be switched between solutions. In my opinion, since we are typically interested in water that is very low on the TDS scale, a dip into distilled water can provide some guidance. It should read near zero. Unfortunately, that is not enough to tell the whole tale.

mabrungard said:

342 solution is one version of a TDS calibration solution. It was formulated to be more like a typical freshwater supply. The other option is a NaCl solution and it is composed of table salt and water...not exactly typical of a freshwater supply. Some TDS meters are required to be calibrated with one solution or the other. Some meters can be switched between solutions. In my opinion, since we are typically interested in water that is very low on the TDS scale, a dip into distilled water can provide some guidance. It should read near zero. Unfortunately, that is not enough to tell the whole tale.

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Much appreciated. Thanks

Tested some RO water from Kroger. 9 ppm, so I'd say they're maintaining their system.

Sounds good.

I ordered mine. I'll see how my local Walmart is doing.

I've got the hm tds ez and it reads 4 straight off my RO unit and has been at 4 for the whole year that I've been running this membrane. Straight off the kingwood, tx tap its 110, ozarka reads about 58.

The only weird thing I have noticed is that if the RO water sits around anywhere, like the RO pressure tank, it reads 7. Maybe that's just the difference in temperature causing that, the tank is in the garage and would be either warmer or cooler, depending on the weather, than the water that comes in from underground.
The water that comes off the ro immediately will read higher, but water that has not been sitting anywhere for any amount of time will always read lower. It doesn't seem like there should be anything that's dissolving into it, but who knows.

We've been an HM Digital Distributor for years.

Russ

Keep in mind that a TDS meter measures conductivity and reads TDS depending on how the table in the meter relates TDS to conductivity. I have always assumed the mg/L numbers were equivalent NaCl (they are in my meter) but in a good meter you can put in anything you like. The temperature correction also depends on the ions involved. Most meters, I believe, have temperature coefficients based on NaCl.

None of this should be important for the use to which homebrewers put their 'TDS' meters which is monitoring the decline in performance of their RO systems.

The HM Digital COM100 for instance has three different user-selectable, non-linear EC-to-TDS conversion factors (KCl, 442TM, NaCl). We find that this feature is important to only a very small minority of customers - none that I'm aware of have been in the brewery industry.

Russ

ajdelange said:

..interesting stuff on TDS meters....
None of this should be important for the use to which homebrewers...monitoring RO systems.

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Buckeye_Hydro said:

We find that this feature is important to only a very small minority of customers - none that I'm aware of have been in the brewery industry.

Russ

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Thanks for the useful information. Mine will just be to check my store bought RO water.

A go/no-go test.

A living legend

Bought another 18 gallons. 6 ppm, and some peace of mind.

Had a chance to test any water yet Gavin?

No RO tested yet. My last brew was an IPA and I just used my tap water with some minerals added.

I did do some repeated tests on my tap water and the readings seem relatively stable over time. Not sure if that is indicative of anything.

TexasWine said:

Bought another 18 gallons. 6 ppm, and some peace of mind.

Had a chance to test any water yet Gavin?

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Just an update to anyone interested.

Tested my RO water form Walmart with the meter I showed earlier.

7ppm TDS. Looks like it and Walmart's RO water are solid.

Gavin C said:

7ppm TDS. Looks like it and Walmart's RO water are solid.

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Please remember that every machine is a separate entity with separate operators. You never know when the unit is going to start to fail. Always rely on your own TDS meter.

mabrungard said:

Please remember that every machine is a separate entity with separate operators. You never know when the unit is going to start to fail. Always rely on your own TDS meter.

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I will. ~$15 well spent I reckon.