pool store calcium test??

[agogley]

Ok, I've taken my water to three different stores and all report low calcium numbers ranging from 125 to 150. However, the home kit I'm using registers are about 250. I'm using the Blue Devil DPD test kit. My DPD test seems to be about 70 to 100 points higher than the pools stores. Consistently.

This has been a big issue for me because I have some sort of crystallization deposits on the sides of my pool. The pool store kept telling me my calcium was 300-400 but my home test said 500-600. So I'd like to avoid having high calcium, but I'm not totally sure if I should trust my home test or not (seems pretty easy...add drops and multiply by 50).

Interestingly, my Jandy Aquapure salt chlorine generator manual suggests a calcium range of 150 to 400 so maybe I ought to stay pat regardless.

 

[benavidescj]

Hi Agogley, welcome to Trouble Free pool!
In order to help you best it is always good to post a set of all of your test results so we can better help you. You should also tell us information about your pool like the volume or size, what type it is, etc.
You mention crystallization deposits (which sounds like scale) on the sides of your pool at CH readings approaching 600 (according to your home test kit). If your pH is consistently held below 7.8, which it should always be, you should not have an issue with scale even at CH of 600ppm.
About your test results, normally we do not like you to take your water to be tested to the pool store because you as the home owner should get more consistent results with a good test kit and testing on your own. However, in this case, since you have taken your water to three different places and have received similar results I would have to go with that and consider your test kit suspect. Having said this, I think that the variation between what the pool store has given you and what you are reading is not all that significant. In other words, your CH is not all that bad. Again, CH and scale can be controlled even at high CH levels of 600 ppm with proper pH control.

 

[agogley]

I'll post my test results tonight and my pool specifics. I struggle to keep my pool under 7.8 in the summer time because of the SWG and the negative edge. Nonetheless, I have crystalling deposits that form on the walls no matter the pool chemistry. However, now with the calcium very low, I've noticed far fewer deposits.

I've often tested water at three different locations on the same day from water taken at the same time and gotten results all over the board. CYA is often the most wrongly read test. It's frustrating to even watch them perform the test because they rarely wait long enough to do the test properly. And then the lighting in the room can affect the readings too.

 

[dorpo75]

I'll post my test results tonight and my pool specifics. I struggle to keep my pool under 7.8 in the summer time because of the SWG and the negative edge. Nonetheless, I have crystalling deposits that form on the walls no matter the pool chemistry. However, now with the calcium very low, I've noticed far fewer deposits.

I've often tested water at three different locations on the same day from water taken at the same time and gotten results all over the board. CYA is often the most wrongly read test. It's frustrating to even watch them perform the test because they rarely wait long enough to do the test properly. And then the lighting in the room can affect the readings too.

At TFP, the premise is knowing what is in your water and being able to test your own water every time for accurate, consistent results and then being able to adjust the water properties to the proper levels. We would recommend you get yourself a good test kit. Folks around these parts usually go with the TF-100. This is a good one and has the needed chemicals and materials to do the tests accurately. I know for a fact that the owner of TFtestkits.net is quick and professional. Soooooooooo get yourself a good testing kit and stop leaving the results to the pool stores. You yourself say it is frustrating to watch them do the testing and are observant in that the lighting can affect the results. :x What are you waiting for? The money spent on a good test kit will save you many times the cost of gasoline running around to the different pool stores leaving you more time to relax and enjoy your beautiful pool. Get your kit now. :!: The reagents should be good for next summer if you store the kit correctly, out of the heat and sun and in a cool location. Good luck.

 

[Bama Rambler]

If you want a very good accurate kit I suggest the TF-100 (see my sig). It includes the FAS-DPD test which you should have anyway and the CH test is in 10ppm drops so it's better than the 50 ppm test you use now. It also includes a good CYA test even of it is subjective. It's better than the pool store's CYA test. You've already discovered they can be wildly inaccurate.

Dora and I are saying the same thing! GMTA