What TDS/EC meter do you use?

[aarhud]

I'm going to purchase a unit soon. Talked myself out of it for years, but I am finally going to bite the bullet.

 

[Simon Morgan]

Why wait? They are £8-£20 on ebay in the UK. I have an HM Digital TDS-3. Which includes a thermometer.

 

[aarhud]

The meters I see mentioned on the forum are usually more expensive. I see the exact model you have on spectrapures website for 24.99 US. I found on another thread that Ted Judy had the more expensive HM digital COM 100. I was not sure if I should spend the extra money, or if a less expensive model would do.

 

[dw1305]

Hi all,

I found on another thread that Ted Judy had the more expensive HM digital COM 100. I was not sure if I should spend the extra money, or if a less expensive model would do.

Simon's suggestion is fine. They are much less complex than a pH meter, so a cheap meter is likely to give you a "ball-park" figure. Temperature has some effect on conductivity, so a temperature compensation is useful. If you can afford a better meter (like Ted's or a Hanna etc) it is likely to be a bit more robust.

Have a look at this thread <http://www.apistogramma.com/forum/index.php?threads/tds-meter.12621/#post-69187>.

cheers Darrel

 

[aarhud]

I literally searched the forum for meters and did not find that thread. I am search function challenged.

 

[aarhud]

Just to update, I purchased the HM digital COM 100. Price difference was $30, so I splurged.

 

[gerald]

So now that you've got a meter, what's the conductivity of your local tap water, rainwater, tanks, streams, & whatever else you're measuring?

 

[aarhud]

Meter just came in today. Tank water measured 95.1 ppm (NaCL conversion factor) at my parents house which I don't think is correct. I'm going to run a few more test later to make sure I did everything right. I just cut the meter on and tested, but no time to play...have to go pick out counter tops.... Can't wait to test the water at my new place. What conversion factor should I be using for TDS in ppm? My options are KCL, 442, and NaCL. And what unit do you guys like for EC, uS or mS?

Big thanks to Gerald, Simon Morgan, DW, Mike, and Tom C for contributing your chemistry knowledge to the forum. Finally feel like I have a basic grasp on things.

Gerald, are you going on the collecting trip Sunday?

 

[dw1305]

Hi all,

Tank water measured 95.1 ppm (NaCL conversion factor)

The NaCl conversion factor is 0.48, so that is 200 microS conductivity.

at my parents house which I don't think is correct.

They are usually pretty accurate, why don't you think that is right? You really can just turn it on, dip it in and 30 seconds later take the reading. If you want to buy a standard the salts in "442" are meant to more closely natural fresh water.

Can't wait to test the water at my new place. What conversion factor should I be using for TDS in ppm? My options are KCL, 442, and NaCL. And what unit do you guys like for EC, uS or mS?

MicroS (uS), if you need to measure in milliS, you've got sea-water. Conversion factors are here: <http://www.eutechinst.com/techtips/tech-tips40.htm>.

cheers Darrel

 

[aarhud]

Tested again, Meter measured 201 microS.I thought the water at my parents house would be harder since the KH and GH are higher.

My tap water at my new place reads:
3 gKH
3 gGH
150 microS

I suspect the values will be changing a lot, since they are doing a lot of work on the water lines around the area. The tap water originally had a 5ppm nitrite reading, but I tested again and it is now reading 0 nitrite. I still have an 1ppm ammonia and 5-10ppm nitrate reading in the tap though. I'm going to use RO water to get the water softer.

 

[gerald]

The ppm/uS ratio for table salt is around .48 to .50, like Darrel says, and for a "typical" mix of ions found in natural fresh waters (Ca, Mg, CO3, HCO3, SO4, PO4, Na, K, Cl, etc) it's usually around .65; City of Raleigh uses 0.67 conversion factor for Falls Lake (Neuse River) water which has 25 to 35 ppm hardness and alkalinity. If Calcium carbonate & Magnesium carbonate were the only ions present (they're not, but let's just pretend) then 7 degrees GH (and KH) would give you around 200 uS. [7 x 18 = 126 ppm / .65 = 191 uS].

So, Conductivity is not very useful for assessing hardness or alkalinity, since each degree of hardness (18 ppm) only contributes about 30 uS, and you cant tell from a conductivity measurement how much of the other ions are present besides Ca, Mg, CO3 and HCO3. If conductivity is really low, like 50 uS or less, then it's definitely soft, but at higher conductivity you can't tell.

Sorry I cant make the SC collecting trip this Sunday - got family stuff going on. Hope you have fun if you go ... bring your meter. NOTE: small fish collected from low-conductivity water (less than 200 uS) are susceptible to Flexibacter infection due to stress-induced loss of body salts, which occurs in the first few minutes after capture. I put 1/2 - 1 teasp/gal salt in the collecting bucket before I start collecting. Salting them after you get back to the car may be too late, especially in warm water.