Low CH with plaster?

Jump to latest Follow Reply
R

RuthN

0
Aug 2, 2015
66
TX
Hey all. I'm fairly new here, but was asked to post a new thread.

ive been testing my water for about a month and CH has always been between 180 and 250. Today, I got 75. I re-tested twice to make sure.

here are my full results.

ph 7.6
FC 4
CC 0
TC 4
CH. 75 (what the heck? How did it go from 220 to 75 in a couple of days?)
TA 120
CYA 70

A fellow poster thinks I need to have CH with plaster and recommended I post a new thread.

i will test again tomorrow, but CH has been consistent until today. What the heck could have happened? I have done nothing unusual.
 
All I can say is it is not possible for water to go from ~200ppm to 75ppm in a matter of days. So either your testing was faulty during the previous CH measurements or something is wrong with your current testing method.

If you have to order the tests in terms of relative difficulty, the CYA test is the one most have trouble with but the CH test is a close 2nd place. Can you please describe exactly what it is you are doing and what the test looks like as you perform it? Pictures would help too. Is your endpoint a sharp and clear color transition or does it seem to take a while for the blue endpoint color to happen (a long transition between purple to blue)? DO you get fading endpoint?

Just do the test again and tell us what you're seeing.

Also, have you ever tested your fill water? If you have, can you confirm that your fill water tests to the same CH value as previous tests?
 
I have never tested my fill water and the CH test drives me nuts. I add drops until I no longer see a change and then subtract one. the only thing I did different today was tested inside. Maybe the lighting was off enough to throw me. I'll re-test tomorrow outside like I have been previously.
 
RuthN said:
I have never tested my fill water and the CH test drives me nuts. I add drops until I no longer see a change and then subtract one. the only thing I did different today was tested inside. Maybe the lighting was off enough to throw me. I'll re-test tomorrow outside like I have been previously.
Click to expand...

What sample size do you use?


Sent from my iPhone using Tapatalk
 
RuthN said:
thats a trick question for me. Lol. Whatever the TF-100 recommends....10ml I think. I don't have it in front of me right now.
Click to expand...

Haha. Ok.

Well there are usually two different sample sizes you can choose based on what resolution you want on the CH test. A 10mL water sample will get you a resolution of 25ppm/drop and the 25mL sample will give you 10ppm/drop. I would suggest that you use the 25mL sample size so that the volume of water is larger and easier to see. I would also suggest doing the test outside with good, indirect sunshine for the best color rendering. You could also place a piece of white paper towel or construction paper being the viewing tube to help bring out the color more.

Are you using a SpeedStir? I find it helps a lot but one thing I've always had trouble with is the 10mL sample size in a SpeedStir. Since the volume is so small and the stir bar is such a large fraction of the water volume, I find it makes seeing color changes more difficult, at least for me. For the 25mL sample size, it's great. But for 10mL sample size, it's not as good. Just my opinion on it.

Report back later and let us all know how it goes. Take detailed mental notes so you can describe what you're doing. Also remember to make sure when adding drops (and this goes for any test) that you hold the dropper bottle as vertical as possible and gently squeeze to deliver the drops. Let the largest droplet size you can form on the tip of the bottle. The droplet should hang for a brief moment so as to develop it's maximum size. Sometimes people try to dropper too quickly and the drops do not properly form.
 
FWIW, my fill water has a CH of 40. I have notes from years ago claiming a CH around 250. So even city water can change albeit probably not over a couple of days. Anyway, for the first time ever in 17 years of owing the pool that came with a house, I had to add some calcium chloride. I have a new plaster (pebble sheen) finish that is about 45 days new and at day 3, I bumped my CH to 230. So about 6 weeks later, after adding who know how much fill water (I have an auto-fill so somehow magically, my pool level has remained constant LOL), I just notice in my weekly 'do 'em all' numbers on Saturdays, that the CH dropped to 220.

I also always use the 25 ml sample so you may find a tad more accuracy there.

And the SpeedStir...the SpeedStir. Honestly, I thought it was gimmick when I got it. Pfffft...how hard is it to mix water...really? After using it, I have to admit that it has become almost as important as the test kit itself and I made room in the test kit and I take it out nightly and polish it. hahaha It really is very nice to have and I believe produces more repeatable results since the mixing is more thorough and more consistent and well, it is just EASIER.
 
Agent99 said:
FWIW, my fill water has a CH of 40. I have notes from years ago claiming a CH around 250. So even city water can change albeit probably not over a couple of days. Anyway, for the first time ever in 17 years of owing the pool that came with a house, I had to add some calcium chloride. I have a new plaster (pebble sheen) finish that is about 45 days new and at day 3, I bumped my CH to 230. So about 6 weeks later, after adding who know how much fill water (I have an auto-fill so somehow magically, my pool level has remained constant LOL), I just notice in my weekly 'do 'em all' numbers on Saturdays, that the CH dropped to 220.

I also always use the 25 ml sample so you may find a tad more accuracy there.

And the SpeedStir...the SpeedStir. Honestly, I thought it was gimmick when I got it. Pfffft...how hard is it to mix water...really? After using it, I have to admit that it has become almost as important as the test kit itself and I made room in the test kit and I take it out nightly and polish it. hahaha It really is very nice to have and I believe produces more repeatable results since the mixing is more thorough and more consistent and well, it is just EASIER.
Click to expand...


I use a plastic spoon. I do not have the speedstir although I am seriously thinking about getting one.

i tested my CH again today outside like I've been doing all along. It was 220. Clearly the lighting made a huge difference.
 
RuthN said:
I use a plastic spoon. I do not have the speedstir although I am seriously thinking about getting one.

i tested my CH again today outside like I've been doing all along. It was 220. Clearly the lighting made a huge difference.
Click to expand...

Get the SpeedStir, you will not regret it!!

Yes, I have experienced that very same phenomenon. I once tested CH indoors and was off (except I got a higher number not lower). I had a really hard time seeing the color transition. When I do it outdoors, I have a much easier time. I also have really high CH (~750ppm) so even at the smaller sample size, it takes a lot of drops to make the color change which adds to the uncertainty.


Sent from my iPhone using Tapatalk
 
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply