Test results after partial drain and refill


LifeTime Supporter
Jun 26, 2007
SF Bay Area
I had pump problems between October 2007 until early May 2008. I had clear water all through this timeframe by adding a gallon or two of 10% liquid chlorine as appropriate for the 100-150 ppm level of CYA. Only when the water temperature reached 60-65 and above in mid-to-late April did I start having problems. Before I knew what hit me, I had quite the algae bloom.

I did a two-pronged approach. I hit the mess with 40-50 PPM chlorine while performing a partial drain and refill. The draining portion ended up taking 3 days or so, for a variety of reasons. I ended up replacing 10,500 gallons of my 23,500 gallon pool, which is about a 45% water replacement, which is great since I was aiming for between a 1/3 and 1/2 drain and refill. The draining process ended at 9PM on Friday, and the refill process took from then until around 1 PM today (Saturday).

The rest of the day involved a continual clean-out of the Polaris 380, which must have happened at least 12 times. The wireless remote (part of the GoldLine/Hayward AquaLogic automaton system) saved quite a bit of time as I could turn off the Polaris cleaner right at poolside, clean out the sock, toss the Polaris back in the water, and turn it back on via the wireless remote, all without having to continually trudge to and from the equipment pad. The algae had turned into fluffy white deposits on the bottom of the pool, which tended to clump together as white strings in the Polaris or in the skimmer basket. The pool is now back to its normal crystal clear state.

The new test numbers taken tonight are as follows:

FC - 16.0 (residual effect of the above-mentioned shocking)
CC - 0,.5
pH - 7.5-7.8 (I realize this number may be off because of the high FC, not to mention I am terrible at color comparisons)
Alk - 80 (was 110 or 120 when tested last summer)
Cal - 170 (this confuses me - my calcium numbers last summer were on the order of 400. The 170 number does not jibe with the previous test result of 400 and my replacement of less than 1/2 the water volume)
CYA - 60-70 (this was read indoors, so I am hoping that an outdoor test tomorrow will show an even lower number. In any case, still a huge improvement over my inherited 100-150 ppm of CYA)
Temp - 71 deg. F.

I think all of my numbers look pretty good, except perhaps for the Calciium reading. Any thoughts or comments?




Mod Squad
LifeTime Supporter
Platinum Supporter
TFP Expert
In The Industry
Apr 1, 2007
Sebring, Florida
How does your water look? Clear?
Are you able to maintain a steady FC overnight?

If the answer to the above in "excellent" and "yes", you are virtually done.

You will find the lower cYA...even if it's 70, to be far more manageable than before and you will mostlikely not have any future algae problems.

Your apparent loss of calcium is puzzling because typically it doesn't go anywhere. What is the CH content of your fill water? That may explain some of it. Secondly, I would get a pool store test. If it matches up on CH then you can add a little bit (I would keep it under 300ppm but more than 200.