Are digital ph/chlorine testers for pool chemistry any good?

Question

Hi all

I've been using the cheap litamus paper style test strips to test my ph, alkanity, chlorine levels etc of my above ground pool. The results are wildly inconsistent, especially across the different brands, even when I can match a resulting colour to the charts. Can't work out if my ph is too high or too low now!

I've seen the tablet type testers and I believe these are supposed to be better... although you still have to colour match I think.

I liked the idea of the digital testers, but are there any reasonably priced ones (below £100/$200), that are any good? I've just read some reviews on the Aquachek digital tester and it sounded really inaccurate.

Cheers

Ross

Answer 1

I've never used litmus paper tests myself, so not sure of the reliability of those. I would presume that they are not too reliable, which seems to be true in your case if your results are fluctuating greatly

I used to work for a pool where we used colour matching tests, but ours used indicator tablets. Basically we'd just bung in DPD1 and DPD3 tablets for chlorine or phenol red tablets for pH, mix it up and compare it to a chart. It was very inconsistent, as the colour I would match the sample to could be different to the colour another person would match the same sample to, usually +/- 0.2-0.4 whilst testing pH, and +/- 0.5 when testing free and total chlorine. Even when finding the colour match myself, I sometimes couldn't match a colour and would wind up guessing!

Since I've worked there, they have bought a digital tester - and the results of that are vastly different to the ones which are found when doing manual testing (they had differences ranging from +/- 0.5-3.0 when testing the same sample of water. I've never used the digital tester myself, although I presume it is more reliable than a human tester.

I think it's hard to know what is best in this situation. I've heard good and bad things about both options. It would be a waste to spend money on a cheaper digital tester that is unreliable. As I've never used a digital tester myself, I have no recommendations for any particular one. I looked up the Aquachek one you mentioned and also found the bad reviews about it - probably one to avoid.

I'd suggest trying out DPD1/3 and phenol red tablets first, as these are not so much of an expense, and I suppose worth trying. The pool I mentioned before still uses this method of testing on a day-to-day basis despite having a digital tester.

Sorry I can't be of more help with regards to specific digital testers. Hopefully someone else with more knowledge in that area will answer!

Edit:

I've been doing a bit more searching around. Most things I've found say to avoid anything like this (http://media.uxcell.com/uxcell/images/it... as they are just a rip off.

Reading your question again, I'm not too sure which type of digital tester you are meaning. There are two types - one where it is completely digital (these have to be callibrated fairly often, so they result you get is only as good at the callibration at the time) and the other type (which I have a feeling you mean) is a colorimeter, where you add the chemical reagents (much like the indicator tablets I have used), and then the tester reads the results by colour matching the sample to a control.

I happened to go to the baths I worked at this weekend, and asked them about their digital tester. I can't remember the make of it, but it would be out of your price range. It cost them quite a lot and they keep it under lock and key! One of the guys recommended the LaMotte ColorQ series (http://www.lamotte.com/pages/pool/colorq... I just did a check on the price of them and the ColorQ Pool 4 comes in at $139.00 here - http://www.eseasongear.com/copo4mekila2.... although I didn't do any shopping around so they may be sold for cheaper elsewhere. The ColorQ Pro 7 Pool Photometer Kit is on sale at the moment for $137.00 on the same site.

I looked up a few review on the Pro 7 and the general feeling seems to be good. It measures free Chlorine, total Chlorine, Bromine, pH, alkalinity, Calcium hardness, and Cyanuric Acid. Reviews seem to show that the accuracy is good. Have a look here for reviews by different people on a forum: http://www.troublefreepools.com/viewtopi... I just had a look on eBay and the Pro 7 is on there - general price seems to be around $140.

Hope that this information is helpful for you.