A Chlorine Reading Question

[Brookenstein]

I hadn't used the tub for a about 4 days, so I decided to put 1 TBS of dichlor in it yesterday afternoon.  ABout 20 minutes later I took a reading my free chlorine was 0.  I was a little confused, but didn't think too much of it.  We went into the tub about 11pm and I put the usual 3/4 TBS in.  This morning I still have a 0 reading.  I have a few different test strips that test for different things... the MPS one has a decent color purple even though there is no MPS in the tub right now (I know chlorine can effect the MPS test strips).  Also my test strips that do Bromine and Free Chlorine show a level of bromine even though I use dichlor, but still the 0 Free Chlorine.

This sounds similiar to when I had super chlorinated and then ended up with high CYA and never could register any chlorine.  I don't have any CYA test strips and don't really feel like going to Leslie's.

My question is this... does it matter?  As long as I know I'm putting a proper amount in, can I ignore the 0 reading?  Do the other reading indicate that yes there is Chlorine in there even though its not showing?

I think I changed the water in mid March last, but it has been perfect (both test wise and visually) up to this point.

TIA!
Brooke

[wmccall]

Sounds like typical "old" water.  As long as it looks clean and doesn't smell bad, your ok.  As for CYA - The HTH test kit from Walmart for $14 measures CYA, although that is all you can do is measure it.

[Brookenstein]

I'm not getting as much time out of my water as I anticipated.  How long do people go between water changes who avg say 6 days/week for an hour day used by 2 people.  I'd say twice a month we let the kids in.  I figured I'd get 3 months easy, possibly 4.  If I change the water now, do I have to put in a new N2 even though it isn't 4 months old.  I vaguely remember seeing something about it won't activate again with new water or somethin'.

[Vinny]

1 tablespoon of dichlor should give you a reading and shouldn't bleach out the chlorine reading. On a 400 gallon tub it is probably about 12 PPM chlorine (1 teaspoon = about 1 1/2 PPM & 3 teaspoons in a tablespoon). I'm not at all familiar with stips but I guess they can be affected by the high chlorine.

I've never heard of CYA (stabilizer) blocking a reading.  Usually a reading will be extremely dark for a while. IF for some reason the chlorine is being used up - it is an indication of a bacteria/algea problem and this is a problem.

From a strip prospective, I've heard negative things about them and I've always use the drop test. I always have a cheap OTO drop tester around to verify or disprove what my Taylor kit is telling me if I suspect it's wrong.

Now if you meant 1 tablespoon (I really can't figure out which is which in the abbreviations) then you do have a problem. 20 minutes should give you a definate reading, you want residue lingering. That's how you know you put enough chlorine into the tub.

[Brookenstein]

Vinny, yes that was one Tablespoon.  I know it should be more than enough to give me a reading.  I was wondering the same thing... is there something in the water eating up all the chlorine and I have a problem OR is it possible something else is going on since the MPS and bromine is changing from the chlorine.

[Vinny]

I gave you WRONG info on the PPM. It's 4.5 PPM NOT 12 PPM.    SORRY!!!!!

If you're using bromine, chlorine WON"T show up ... bromine converts chlorine to bromine.

[Brookenstein]

I'm using dichlor, but some of my test strips have a spot for Bromine and that did change along with the MPS, event though its been nearly 2 weeks since I used MPS.

[Mendocino101]

I gave you WRONG info on the PPM. It's 4.5 PPM NOT 12 PPM.    SORRY!!!!!

If you're using bromine, chlorine WON"T show up ... bromine converts chlorine to bromine.

Vinny....thank you.....I was trying to figure how you came up with that number.....

[Mendocino101]

I'm using dichlor, but some of my test strips have a spot for Bromine and that did change along with the MPS, event though its been nearly 2 weeks since I used MPS.

What strips are you using...the 4 tab from Aqua Check measures Ph, free chlorine. total alk and Cyanuric acid...here is a link about the comapny who makes them.... http://www.hach.com/hc/static.template/templateName=HcCorporate.HcHistory.htm/PREVIOUS_BREADCRUMB_ID=HcCorporateHcCorporatehtm/SESSIONID|B3hNVFE0TnpVM05UUXdNemt3Sm1kMVpYTjBXUT09QVU5RlQwYw==|

[Gomboman]

That's a strange problem Brooke. One teaspoon of dichlor gives me about 2-3 ppm Free Chlorine after 20 minutes. I use a Taylor test kit though and haven't had much luck with test strips. Do you normally get normal values with your test strips or has it been a while since you've used them?

Theoretically, there would have to be something is your water to deplete a tablespoon of dichlor in 20 minutes. Maybe your test strips are bad?

[Brookenstein]

So, should I superchlorinate and see if I get a reading?

I've only ever used test strips and they have worked fine.  I usually only test weekly or less.  I tried a few different brands and nothing registered.

[Gomboman]

So, should I superchlorinate and see if I get a reading?

I've only ever used test strips and they have worked fine.  I usually only test weekly or less.  I tried a few different brands and nothing registered.

I'm not an expert but it shouldn't hurt anything? I have the same spa and Superchlorintate with 2 Tablespoons. How much do you normally use? It's supposed to be 10x your combined chlorine level. Without a Test Kit it's hard to measure. I would put in your normal shocking dose and take a measurement. You should have a strong signal after Superchlorination.

[Brookenstein]

Hmmm... I just did an experiment.  I added 1 TBS of dichlor and then about 1 minute later I tested in the filter box, the color was dark purple.  A couple minutes later I added 1 more TBS and then tested the general water area.  The color was white.  So I tested in the filter area again... and white.  So this leads me to believe that it is bleaching the test strips.  I'm leaving the cover off for a bit and will test again later.  I think I'll put it in my plans to change the water soon.

[Gomboman]

Hmmm... I just did an experiment.  I added 1 TBS of dichlor and then about 1 minute later I tested in the filter box, the color was dark purple.  A couple minutes later I added 1 more TBS and then tested the general water area.  The color was white.  So I tested in the filter area again... and white.  So this leads me to believe that it is bleaching the test strips.  I'm leaving the cover off for a bit and will test again later.  I think I'll put it in my plans to change the water soon.

Brooke, I would be lost without one of these.

http://www.azpartsmaster.com/shopazp/Pool+Water+Test+Test+Kits+-+Taylor+(TAY-TK).html

[Brookenstein]

I tested the water about 30 minutes later and had 5ppm.  I decided to test with the other brand strips and I had 0.  So I went back and tested with the first brand and had 0 again.  WTF?  I don't get it.

I know this is gonna sound stupid, but my water is always perfect until its not.  I really think this is a sign that its time to change the water.  I will look into getting a liquid test kit one of these days.