Newbie with test #'s

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grivera

0
Jul 3, 2007
89
Maryland
Hi all, I just shocked last night (1st time) at about 9:30 pm based on recommendation of service dept. guy who stated do it one week after indoctrination and the fact that we had a pool full of kids day this past Thursday (and several kids in since first day). The pool is less about two weeks old, plaster stillbeing brushed 3+ times a day. I also have a floatee opened half way with 3 trichlor pucks in it as opposed to skimmer recommended by service dept. Pump is still running 24/7. This is based on 18563 gallons:

CH-off chart (3.0+)
CC- of chart (6.0+)
PH- 8.2
ALK- right about 20 or a little lower.

FWIW, this is using a $11. Swimline test kit from Namco pool store.
 
With a new plaster pool you need to keep a constant eye on the PH and bring it down reguarly. Try to hold the PH between 7.2 and 7.8. You bring PH down with acid, either muriatic acid or dry acid (sometimes called PH down). While the plaster is curing, probably several months, it will be constantly raising the PH.

Trichlor pucks will act more slowly in a floater than in the skimmer. They can go in the skimmer as long as the pump is running 24/7. You probably only want to use them for the first month or two and then switch to bleach. When starting up a plaster pool the trichlor will add chlorine, add CYA, and lower PH, all of which you want. Later you will want to stop adding CYA, and so need to stop using pucks.

CH normally stands for calcium hardness and is typically a number between 20 and 600. That makes me wonder about CC, which could be 6+, though that would be somewhat surprising. Could you check what those two readings are indicating according to your test kit? The best investment in your pool you can make is a good test kit. TF Test Kits sells a wonderful test kit.

You will want to bring the alkalinity up to somewhere around 100 for now. This can be done by adding baking soda. Baking soda will also raise the PH somewhat, which will then need to be brought back down with more acid.

Now might be a good time to read some of the articles in The Stickies section of this site, see the link in the sub-heading of any page. The first article on BBB and basic chemistry is particuarly good.
 
You are going to want to add somewhere around 20 lbs of baking soda. You should split that up into two or three steps. Each step involves lowering the PH below 7.5, add some baking soda, let it circulate for a couple of hours, and then retest and see where you are. It is best to split it into a couple of steps because none of the numbers are likely to be exact, so you might overshoot or undershoot. Also, because the baking soda will raise the PH you don't want to do it all at once and allow the PH to go to high.

You can use my Pool Calculator, see my signature for a link, to calculates amounts. Keep in mind that with your current very low alkalinity the pool calculator won't be able to calculate PH changes accurately. With your alkalinity that low it should only take one cup of muriatic acid to lower the PH dramatically. As your alkalinity goes up it will take more acid to change the PH.

If your combined chlorine is really 6 then you need to shock your pool to bring the CC level down below 0.5. Shocking the pool involves bringing the free chlorine level up to the shock level based on your current CYA level. Since you probably don't know your CYA level you either need to get that tested or guess what it might be.
 
Thanks. Some yellow stains that had left have returned to my pool in the last couple of days, in the same area. Could my water have metal in it? Also, I was reading my A&S manual last night and it says not to add more than two pounds of baking soda at once. Then it says if my TA is below 50, to not add any till I get the water tested for metals. I called the closest pool store (Leslies) and the clerk said he can test the water for metal but if my CH is above 1ppm, thetest may give a "false positive".

If I do have metal in teh water (which may be causing my staining), is it still safe to go against the manual and add the necesary baking soda? FWIW, I''ve already addede 6 pounds in two increments (2 last night and 4 this morning).

I'm really at a loss here, and I don't want to make the problem I have worse. My water is crystal clear otherwise and I have to triuchlor tabs in each skimmer now. Oh, I also addede a quart of acid last night. testing this morning didn't reveal a change in the ALK. I will go to Leslies today and have them test my water and post the results.
 
Yellow stains could be iron. You can confirm iron by rubbing a stain lightly with a sock with crusched vitamin C tablets in it. If the stain disapears around the sock then it is most likely iron. Iron stains are very PH sensitive, raising the PH will cause the stains to appear. The increase in PH from the baking soda could have been enough, though if you lowered the PH with acid first I wouldn't have expected that. Iron needs to be treated with a metal sequesterant.
 
Ok, tehse are my test results from Leslies and Anthony and Sylvan (A&S are computer analysis). I took the water sample after putting in the 4 lbs. of baking soda.

Leslies:

FC 5+
TC 5+
PH 7.5
TA 80 (go figure)
Calc. Hard 220
Cy Acid 30
TDS 250

A&S:

FC 1.42
TC 1.74
PH 7.5
Calc. Hard. 170
TA 100
Cy Acid 45
Copper .71
Iron 1.47
TDS 150

I am adding a metal magnet (blue shield brand) tonight to get metal out ALSO adding Calcium hardness. Is this a good plan, any other suggestions?--Could the TA test have been off due to me recently adding baking soda?
 
It can take a couple of hours with the pump on for the baking soda to disolve and mix into the water throughly.

Keep in mind that the tests are not completely precise. The two sets of pool store numbers could plausibly agree on everything except chlorine given the potential errors in the tests. And chlorine often seems to "vanish" somewhere along the way to the pool store, so I am inclined to believe the higher chlorine numbers.

Calcium can cloud the pool if you add too much at once or if the PH is too high. Metal sequesterants will typicaly either lower the PH or leave it alone. I don't see any problem, but I would still add the sequesterant first and then give it an hour before doing the calcium.
 
Thanks. I added the metal magnet but according to the back of Leslies paper on the chemicals, it said not to add the calcium on the same day as baking soda, so I'll wait till tomorrow night to add the calcium since I added baking soda this morning.
 

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