CH rising?

[chem geek]

Donnie,

Great minds think alike. I did exactly the same thing after you posted your CH results. Like you, I found that chlorine tests did not appear to be temperature dependent. In fact, the chlorine test seems to be TIME dependent where waiting too long to do the test has the chlorine level drop so it's more important to do the test quickly than to have it be at room temperature.

I did not get the same results as you did with the pH test. I found the pH to drop as the water warmed up and that is actually what I expected since there are technical reasons that should be the case. It doesn't drop that much, however, since it theoretically is only around 0.1 unit from 50 to 70, but from 45-50 to 85 it should be around 0.2 units which is much more noticeable. I heated the sample in my hand to simulate "heated" pool water and got the pH to drop more noticeably (I also kept the container covered during the test to prevent "natural" pH rise from outgassing).

I also didn't find as much variation as you did with the CH test. I did find a small variation, but only a couple of drops difference (i.e. 20 ppm) which isn't much.

I am somewhat conflicted regarding recommending that ALL tests be done at room temperature. I think the pH test is best done at actual temperatures since pH is supposed to vary with temperature and the chlorine test loses accuracy if you wait too long. So perhaps, all tests but pH and chlorine should be done at room (or "warm" water, if in the summer) temperature or if you let water warm up for the chlorine test -- cover the container while waiting.

Richard

[DONNIE]

Richard, Do you use the standard Taylor Ph color test or do you use something more elaborate? I may have had a small difference but not a noticable one. What do you anticipate the salt test results will be a cold vs warm temps will be?

Donnie

[DONNIE]

Thanks Waste. I'm really having fun now that I am understanding whats going on with my pool. It's really a fairly basic science that everybody (including myself) finds overwhelming at first. The more I learn, The easier it becomes.

Donnie

[chem geek]

Richard, Do you use the standard Taylor Ph color test or do you use something more elaborate? I may have had a small difference but not a noticable one. What do you anticipate the salt test results will be a cold vs warm temps will be?

Donnie

I just use the standard Taylor pH colorimetric (i.e. "match the color") test. I did a salt (chloride) test on my pool, but only did it at one temperature. I was surprised to find that I had between 800 and 1000 ppm salt in my pool since I effectively diluted by 50% twice two winters in a row, though not last winter nor this winter, and I've only used chlorinating liquid -- only about 0.5 ppm per day in the summer and hardly any demand at all in the winter. So I expected around 500 ppm or less. I must have had a MUCH higher TDS than I thought in the past. Either that or the salt test is temperature dependent. My guess is that it isn't. The silver nitrate is a pretty strong one-way reaction so I wouldn't expect the indicator change to be very temperature dependent. Of all the tests, it's the CYA test that is probably the MOST temperature dependent (due to the partial solubility of melamine cyanurate, though see this post for more info about that).

Richard

[CarlD]

Posting at 3:53am? Richard, you're too much into this for the winter!

Remember one thing about the salt: The "inert ingredient" in Liquid Chlorine/Bleach is, of course, brine/saline/saltwater. That's probably the cause of your salt rising.

Bleach is made from saltwater.

[chem geek]

Posting at 3:53am? Richard, you're too much into this for the winter!

Remember one thing about the salt: The "inert ingredient" in Liquid Chlorine/Bleach is, of course, brine/saline/saltwater. That's probably the cause of your salt rising.

Bleach is made from saltwater.

It was 12:53 AM on the west coast where I am, but you're right, that's still late.

I figured with the 0.5 ppm FC average addition per day and that 1 ppm FC adds 1.6 ppm of salt (0.8 ppm from chlorine that becomes salt when it gets used up plus 0.8 ppm of salt directly) that over 7 months of summer use that is 0.5*1.6*7*30=168 ppm. I guess two seasons of that plus the small amount over winter plus what was leftover and diluted from previous seasons plus the 280 ppm from the Calcium Chloride adds up to at least 616 ppm. If I had around 200 ppm leftover from previous seasons diluted in half each season that gets me to over 800 ppm. When I did the math last night, it didn't work out, but then again that's what I get for trying to "think" at 12:53 AM!

So cool. Now I've got one of those near-1000 ppm salt pools. I wonder if my wife will notice anything different.

Richard

[CarlD]

Wait a minute, just a doggone minute!

Did you say SEVEN months of summer use a year???

With a lot of luck we can maybe get 4 1/2 months of use a year: Most of May, all of June through August, and maybe half of September, if and only if it's not raining all month. And that's WITH solar panels! Without, it would be part of June, and July and August.

You really know how to hurt a guy from New Jersey, don't you!

[chem geek]

Carl,

If it makes you feel any better, from mid-April to mid-May and from mid-October to mid-November we heat with lots of gas assist and it's EXPENSIVE, a few hundred dollars for each month. So we really only have FIVE months of true solar-only heating time and we still have a few days here and there where we use gas assistance since we keep the pool at 88F if we can (or at least 86F). I think we only use NO gas for a month in July. All other (swim-season) months have at least one day that needs gas due to the sometimes cloudy day or long foggy morning. If I really wanted to make you jealous, I'd be living in southern CA or AZ or southern FL.

Richard

[DONNIE]

88 degrees sounds warm. I haven't even been in mine since construction but hopefully anyday we will get out of this deep freeze. I have a 200K btu heater that I hope wont be too expensive to heat 9K gallons so we can use ours mid March thru September.

Donnie

[waterbear]

Carl.
Hate to make you feel even worse but how about 9-10 months a year (with the heatpump going for about 4-5 of them). Oh, the hottub gets used in the other 2-3 months! This is why I no longer live in New Jersey I hope to add solar in the next few years once my piggy bank recovers from the pool builder from h*ll that I still am fixing so don't begrudge me this one!