Testing results, need advice

[mer1844]

We have a small 14 x 28 in-ground vinyl liner pool that we had installed last year. I haven't had any problems keeping the water clean and clear, but wanted to post my latest test results to see if I can make it any better.

Oh, and the pool does have a Nature 2 system on it.

Yesterday morning after a night of heavy rain, I checked my TC and PH levels. The TC level was 0, the PH level was 7.5. To me, the water also had some what of an oily feel to it.

I put a 1lb bag of shock in the pool and tested the water last night.

Those test results are:

FC 6
CC .5
TC 6 (ballpark figure, I have a hard time judging colors)
PH 7.5
ALK 110
CAL 80
CYA 45


After doing some reading on the forum, I decided to remove the chlorine pucks from the pool today, and test again tonight.

Tonights test results:

FC 1.5
CC .5
TC 3 (again, a ballpark figure)
PH 7.5
ALK 110
CAL didn't test
CYA 40

How do these test results look? What should I be doing differently?

Should I discontinue the use of tri-chlor pucks?

Thanks for any insight.

[CarlD]

FC 1.5
CC .5
TC 3 (again, a ballpark figure)
PH 7.5
ALK 110
CAL didn't test
CYA 40


Ok, you need a proper drop-test kit because some of these numbers don't make sense, and I can see you are using test strips. Strips are a lousy alternative to drop-testing.

Here's a rule: TC =FC + CC.
If it doesn't something in your testing is wrong, by definition. If your FC is 1.5, and your CC is .5, then your TC is 2. If your TC reading is 3, then one of the 3 readings MUST be wrong, by definition.

Also, I noticed your CYA dropped from >100 to 40. That can ONLY be a testing error unless you replaced 60% of your water.

ASSUMING your FC and CC numbers are correct, and your CYA number is correct, you need chlorine for 2 reasons:
1) you need to shock out the CC so it goes to 0--raise FC to 15 to do this.
2) You need to never let FC go below 3 if your CYA is 40.

[mer1844]

Ok, you need a proper drop-test kit because some of these numbers don't make sense, and I can see you are using test strips. Strips are a lousy alternative to drop-testing.

Here's a rule: TC =FC + CC.
If it doesn't something in your testing is wrong, by definition. If your FC is 1.5, and your CC is .5, then your TC is 2. If your TC reading is 3, then one of the 3 readings MUST be wrong, by definition.

Also, I noticed your CYA dropped from >100 to 40. That can ONLY be a testing error unless you replaced 60% of your water.

ASSUMING your FC and CC numbers are correct, and your CYA number is correct, you need chlorine for 2 reasons:
1) you need to shock out the CC so it goes to 0--raise FC to 15 to do this.
2) You need to never let FC go below 3 if your CYA is 40.


I use a PS233 Complete Swimming Pool Testkit from Pool Solutions that I purchased last summer. Not test strips. I follow the directions step by step as printed on the inside top cover of the kit.

As I stated in the post, when using the PS-200 OTO/Phenol red test kit, I have a hard time determining the exact colors of the lighter yellows for the chlorine readings, so the reading could very well be 2 instead of 3.

The CYA didn't drop from 100 to 40. It dropped from 45 to 40, but I did backwash and rinse the filter this morning, and then added water. This may account for the drop.

[CarlD]

I must have read something wrong...I thought I saw CYA >100...Sorry.

Still, TC = FC + CC. If you use the FAS-DPD test for chlorine you shouldn't use the TC test in the PS-200 portion--calculate TC by the formula. Usually, such discrepancies indicate a test strip...Another "Sorry!" from me.

My advice, though, hasn't changed:

1) you need to shock out the CC so it goes to 0--raise FC to 15 to do this.
2) You need to never let FC go below 3 if your CYA is 40..

With CYA of 40, you should use bleach or liquid chlorine for your chlorine and shocking and not tri-chlor tabs.

[mer1844]

Thanks, for your help.

[waterbear]

Also dump the N2. It really isn't doing anything and you are just wasting money on the cartridges for it!

[duraleigh]

mer1844,

The most interesting thing in your test results to me (thanks for posting good, complete numbers) is the 4.5 drop in FC over a 24 hour period. That's a little excessive in a normally operating pool....most folks drop 2-3ppm.

So, you probably have some organics in your pool and shocking is the way to get them out. Rather than "a 1lb bag of shock", it is important you understand that the idea is to get your chlorine to breakpoint...in your case about 15ppm..no less.

Calculate your pool gallons and add appropriately....probably closer to 2lbs of Cal Hypo but I don't know how many gallons are in your pool.

This should improve your water clarity (if it needs it) and get rid of the CC's in your pool.

Like Evan said, save the money and get rid of the nature2 cartridges.

All else is well.

[mer1844]

Dumped in 3 gallons of 6% bleach this morning. That brought the FC up to 15.5 with a CC of 0.

For the Nat 2 issue; I'll use it the for the rest of this season because I replaced the cart only a few weeks ago. I won't use it next year. When I close the pool for winter, out she goes.

Thanks for the help.