Is this TDS meter good?

[ajremington68]

Is this a good TDS meter? (Amazon)

HM Digital DM-1 In-Line Dual TDS Monitor, 0-9990 ppm Range, +/- 2% Readout Accuracy,Blue & White​

Amazon.com

And is this a good meter? (Amazon)

TDS Meter Digital Water Tester, Lxuemlu Professional 3-in-1 TDS, Temperature and EC Meter with Carrying Case, 0-9999ppm, Ideal ppm Meter for Drinking Water, Aquariums and More​

2025 Upgraded TDS Meter Digital Water Tester, Lxuemlu Professional 3-in-1 TDS, Temperature and EC Meter with Carrying Case, 0-9999ppm, Ideal ppm Meter for Drinking Water, Aquariums and More: Amazon.com: Industrial & Scientific

2025 Upgraded TDS Meter Digital Water Tester, Lxuemlu Professional 3-in-1 TDS, Temperature and EC Meter with Carrying Case, 0-9999ppm, Ideal ppm Meter for Drinking Water, Aquariums and More: Amazon.com: Industrial & Scientific

a.co

What are the differences? One hooks up to your rodi the other doesn't? Is the handheld any good for the price? A lot of the reviews of the handheld refer to people testing tap water, has anyone compared a handheld to a TDS that hooks up to a RODI unit, are they comparable? Have not tested my TDS and my unit is about 5 months old and want to as I bet it's time to change out some filters.

 

[Mr. Mojo Rising]

I bought a cheap handheld TDS meter from amazon for $15, it has worked fine for me for years. I don't think its complex technology, so any any cheap unit should do. I use it so rarely, maybe once a year (after all why would you use it often?), I just don't think its worth spending much money or thought on (though others might have a different opinion).

 

[ajremington68]

I bought a cheap handheld TDS meter from amazon for $15, it has worked fine for me for years. I don't think its complex technology, so any any cheap unit should do. I use it so rarely, maybe once a year (after all why would you use it often?), I just don't think its worth spending much money or thought on (though others might have a different opinion).

how often do you test your RODI unit?

 

[Mr. Mojo Rising]

how often do you test your RODI unit?

Almost never. I figure why should I? If it reads zero the first couple of times I use it, it will always read zero. Every time I’ve randomly checked it has showed zero. My tap water reads .178 so I know it works. There is enough to worry about in this hobby, this is not a consideration to me at all.

 

[Buckeye Hydro Verified Sponsor]

With a RODI system, you want to know the TDS in THREE locations

• tap water
• RO water
• DI water

So no, I'd not recommend the DM1 to you. This is a meter we recommend for RO systems, not RODI systems.

A better choice would be the TRM1 - a THREE probe meter.

Russ

 

[F4u-SuperCorsair]

how often do you test your RODI unit?

Every time I make fresh water. I throw away the water until the meter says less than 10 tds.

 

[ProvidenceTidalReef]

With a RODI system, you want to know the TDS in THREE locations

• tap water
• RO water
• DI water

So no, I'd not recommend the DM1 to you. This is a meter we recommend for RO systems, not RODI systems.

A better choice would be the TRM1 - a THREE probe meter.

Russ

If you check with the manufacturer they actually hide the fact the 3 meter dosent work with RODI units for saltwater. It only test for TDS of drinking water. Not suitable for testing for aquarim use. According to HM when i contacted them. So not sure exactly what the diffrence is mabye the way it measures and the power required to make the measurement? I didnt get a very clear answer only vague and kinda beating around the bush. But they did say to get the 2 sensor unit that it would serve me better.

Ive been just changing my carbon every 6 months and my resin every 3. My micron filter i change every 1 year as it dosent build up much orange color or any color till about that ammount of time. The membrane i change 1 time every 2-3 years.

I have never tested for TDS one time in 7 years being in the salt hobbie and about 11 years in fresh.

So is it 100% nessassary.. id say probbly not. Depending on the water report in your area. But on the other hand a peice of mind is always good to have and a starting point if things start going down hill always helps...

So this is why i am finally getting around to it...

Hope this helps in someway or another, best of luck to all of you

 

[Reef.]

A good quality pen type is all you need, easy enough to take tap and finished water tds and for the odd time you need to take the tds after the membrane and before the resin you just pull out the tube which literally takes 2 seconds. An inline meter is not required.

Some tds meters read below “zero” so 0.9 down to 0.1 etc depends how precise you want to go, a lot of the cheaper ones only read to zero which still leaves a lot of tds going into your water.
Most people would shudder thinking of adding po4 at 0.9 to their tank but you could be adding a load of po4 and other stuff too if you settle for a cheap meter.

 

[Buckeye Hydro Verified Sponsor]

If you check with the manufacturer they actually hide the fact the 3 meter dosent work with RODI units for saltwater. It only test for TDS of drinking water. Not suitable for testing for aquarim use. According to HM when i contacted them. So not sure exactly what the diffrence is mabye the way it measures and the power required to make the measurement? I didnt get a very clear answer only vague and kinda beating around the bush.

I do not believe this is accurate. HM has some new people - one of them may have given you less than accurate information.

As background - I worked with HM years ago to get them to come out with the three probe TRM1.

Russ

 

[Reef.]

I do not believe this is accurate. HM has some new people - one of them may have given you less than accurate information.

As background - I worked with HM years ago to get them to come out with the three probe TRM1.

Russ

Think the person maybe heard ‘saltwater’ or ‘rodi’ and was confused as I can’t think of why knowing drinking water contains a lot of tds would be useful, surely low tds in drinking water would be more useful to know, so I would think the device would be designed to measure low TDS.

 

[BryanM]

Is this a good TDS meter? (Amazon)

HM Digital DM-1 In-Line Dual TDS Monitor, 0-9990 ppm Range, +/- 2% Readout Accuracy,Blue & White​

Amazon.com

And is this a good meter? (Amazon)

TDS Meter Digital Water Tester, Lxuemlu Professional 3-in-1 TDS, Temperature and EC Meter with Carrying Case, 0-9999ppm, Ideal ppm Meter for Drinking Water, Aquariums and More​

2025 Upgraded TDS Meter Digital Water Tester, Lxuemlu Professional 3-in-1 TDS, Temperature and EC Meter with Carrying Case, 0-9999ppm, Ideal ppm Meter for Drinking Water, Aquariums and More: Amazon.com: Industrial & Scientific

2025 Upgraded TDS Meter Digital Water Tester, Lxuemlu Professional 3-in-1 TDS, Temperature and EC Meter with Carrying Case, 0-9999ppm, Ideal ppm Meter for Drinking Water, Aquariums and More: Amazon.com: Industrial & Scientific

a.co

What are the differences? One hooks up to your rodi the other doesn't? Is the handheld any good for the price? A lot of the reviews of the handheld refer to people testing tap water, has anyone compared a handheld to a TDS that hooks up to a RODI unit, are they comparable? Have not tested my TDS and my unit is about 5 months old and want to as I bet it's time to change out some filters.

NOthing wrong with that one at all.

I also have a handheld "pen" style one as well.

 

[ProvidenceTidalReef]

NOthing wrong with that one at all.

I also have a handheld "pen" style one as well.

How often are you calibrating yours and what solution do you use for it?

 

[BryanM]

How often are you calibrating yours and what solution do you use for it?

I do not calibrate either of them (inline for rodi, or pen style).

If I wanted to test the handheld TDS meter I'd probably use distilled water.

 

[ProvidenceTidalReef]

Think the person maybe heard ‘saltwater’ or ‘rodi’ and was confused as I can’t think of why knowing drinking water contains a lot of tds would be useful, surely low tds in drinking water would be more useful to know, so I would think the device would be designed to measure

I do not calibrate either of them (inline for rodi, or pen style).

If I wanted to test the handheld TDS meter I'd probably use distilled water.

How do you verify. What would you test aginst to be sure?

 

[BryanM]

How do you verify. What would you test aginst to be sure?

I've never read that you need to calibrate that inline TDS meter, or the handhelds.

Like I said, I'd test with distilled water if I were concerned or curious.

I calibrate my refractometer with fluid specific for that.

 

[ProvidenceTidalReef]

I do not believe this is accurate. HM has some new people - one of them may have given you less than accurate information.

As background - I worked with HM years ago to get them to come out with the three probe TRM1.

Russ

Apprently its due to the probes of the units being comprised of diffrent metals, some offer more resistance and some less. Example: titanium and aluminum dont conduct at the same rate.

 

[ProvidenceTidalReef]

I've never read that you need to calibrate that inline TDS meter, or the handhelds.

Like I said, I'd test with distilled water if I were concerned or curious.

I calibrate my refractometer with fluid specific for that.

Ahh okay. What i have gathered is they can be anywhere between 2ppm and 300ppm diffrence due to them not being calibrated 100% from factory. Not anecdotally, there os proof of them being or going out giving faulse readings. So idk ill try the hm1 thing for 15 bucks on the amazon and try it out i guess.

 

[X-37B]

I use this. My inline rodi tds meter will read up to 3 before my handheld moves from zero. I use the solution to verify probe is accurate.
I change my rodi filters when my inline reads 2.

 

[KStatefan]

Apprently its due to the probes of the units being comprised of diffrent metals, some offer more resistance and some less. Example: titanium and aluminum dont conduct at the same rate.

These are monitors for TDS on a fresh water RODI systems there is no saltwater involved.

 

[ProvidenceTidalReef]

These are monitors for TDS on a fresh water RODI systems there is no saltwater involved.

Its not the saltwate thats the problem . Its being used to mix salt, drinking water rodi same thing you get in a bottle of figi water. Has a higer acceptable level of minerals *TDS* that differs from you useing it to mix your salt.
That water should have less than acceptable numbers for drinking.

On the page you can see they even tell you it wont read past a certan number up or down and it does tell you there will be a diffrence of +or- 3 tds any given way. 0-999ppm ish.

But an acceptble level of TDS for driking is about 10-20 so most manufacturers calibrate the drinking water units to measure 0 when infact there is 3-20ppm tds.