Hanna InstrumentsHI 98121 Combination pH/ORP/Temperature Tester

I bought the Hanna HI 98121 meter to test swimming pool water. I have never used a pH/ORP meter before and did not know quite what to expect. It required a lot of effort to get it working, but in the end it works well and I am happy with it.As others have found, the storage solution shipped in the cap had dried up. I was unable to get the pH reading to stay in calibration and the ORP function gave erratic results. So I exchanged it for another of the same model.The replacement meter had exactly the same problems. The instructions say to soak it for one hour in HI 70300 storage solution if the pH electrode had dried out. However, I had to soak it for 4 days before the pH reading would stay in calibration.The ORP function was still somewhat erratic, went way down if the solution was stirred, and took as long as 90 minutes to settle to a stable value. The instructions recommend soaking in HI 7061 cleaning solution to clean the electrodes, but that did not help. Hanna also recommends polishing the ORP electrode with jeweler’s rouge, but that did not help either. Some other manufacturers recommend polishing the platinum ORP electrode with baking soda. I gently polished the platinum ORP electrode several times with baking soda on a moistened Q-tip and it worked! The ORP function now gives a stable reading in 2 to 4 minutes. (Do not polish the glass pH electrode.)Since both meters I tried arrived dried up, I suspect the initial problems may have been due to old stock or improper storage rather than a manufacturing defect. I have read that pH electrodes have limited lifetime, even in storage, so I would try to find a source of fresh stock if I bought again.The meter requires additional purchases of HI 70300 storage solution and HI 7061 cleaning solution as well as pH 4.01 and pH 7.01 calibration solutions to calibrate it and keep it working.This model has a replaceable pH electrode, (p/n HI 73127), but it does not have the renewable reference junction that some other Hanna models have.In summary, the meter did not work as received, and it required quite a bit of research and effort to get it working. Someone more familiar with this type instrument would probably have less trouble. However, it is now working well and gives easier and more precise readings than a standard pool test kit.UPDATE APRIL 12, 2016. As mentioned above, I was originally able to get this meter working fairly well. However, it soon developed problems again. The ORP reading got slower and slower, taking over an hour to settle. Cleaning the electrode did not help. Then the pH reading got slower and slower. I bought a replacement probe ($53) directly from Hanna to (hopefully) avoid any problems with old stock. However, the storage solution packed with the new probe had long-since dried up, and its performance was even worse than the original one. It takes about 1.5 hours to get a stable pH reading in pool water.After 2 years of frustration, I have found the Hanna HI 98121 meter to be an expensive instrument that never worked well. The yellow pH meters that sell for under $20 work better. I would not buy it again or recommend it. I am downgrading my rating from 4 stars to 2 stars.

Just received the unit today. After trying to calibrate pH. Wasnt able to calibrate it.After a few minute. One of the battery exploded with a big bang.Try to return it. Its impossible. Try Amzon associate. No answer! Very disapointed of the quality of service.Stay away from that company. The minimum warranty here in quebec is 10 days!

Half the time it gives stable results that settler quickly and give me confidence that it's doing a good job. On the occasions where I cross-checked it against other methods (more on this in the next paragraph) it has matched well. The calibration was pretty decent out of the box but I did a 2-point calibration in pH 4 and 7 buffers anyway just to be sure.However the other half of the time this thing randomly jumps throughout the full pH range of 0-14. I haven't proved it to myself yet but it might be getting influenced by my cell phone which was in my pocket on all of those erratic incidents. pH meters need to be absurdly sensitive because the resistance of the sensing cell is roughly 10 billion ohms. It's like the most sensitive volt meter you will ever see. They aren't easy to make well, and frankly, this thing is nearly at the rock bottom of the price range. From now on I'll leave the cell phone elsewhere when I use the meter.I use it in both our hot tub (where the ORP function is a good way to be sure I get enough but not too much shock treatment into the water), and our fish pond. Of course it should be rinsed well clean water after every use, and consider it mandatory to use the storage solution (I use the Hanna 70300M) when you put it away. That will keep the pH bulb and the reference wick very happy for years. You don't need to be a chemist (I am one) to get good results (at least some of the time), you just need to follow the direction sheet.

I bought this for 130 USD in the summer of 2015 for pool testing; my water is just too weird for the standard "amount of chlorine" tests to work reliably, and I had the algae to prove it. Well, ok, it is not a magic wand and I still battle the algae, but the Hanna tester itself just keeps on working and, so far as I can see, keeps on being accurate.I use Hanna's 70300 storage solution, a little in the cap each time. I think it's just a salt solution. When you close the cap it squirts in your face every time however I haven't died yet. I also have Hanna's 7160 cleaning solution, which I used today for the first time (in three years., still in date!) and it didn't seem to change anything. I think the latter is probably just a solution of a persulphate oxidizer; the instrument itself reports a pH of 1.6 and an ORP of 860mV while it is immersed.

After a few years of trying to read litmus strips, I bought this pH tester. My hot tub water quality has never been better. If you keep the pH between 7.2 and 7.6, the chemicals can do their job to keep the water clear and sides of the tub free from 'gunk'.My only negative comment is minor. When it arrived, it was all I could do to get the black plastic cap off of it. When it was last calibrated, nobody bothered to rinse the test chemical off. I had to clean the tester before it could be used. The tester works fine.