Calcium Hypochlorite or Algae

[EmEeTee]

We just installed this pool this summer, previously we had a 10k gallon round pool. It had been open just a couple of weeks when problems started. 5 weeks ago it rained for a couple of days and the weather was very warm, the top of the water was beginning to feel slimy but not terrible so I shocked my pool. The next morning the entire bottom was covered in white and brown sand. I've never seen anything like it. I assumed it was dead algae, vacuumed it up.

The next day more stuff appeared on the bottom of my pool, I'd vacuum or brush it and it just kept coming back in the same spots. Shocked it again but didn't seem to do anything, except turn more white or grey dust.

As days went on I went to the pool store and they told me it sounds like mustard algae. We treated for mustard algae with Cal-hypo, triple shocked one day, then quadruple shocked the next, but it just kept coming. Brushed several times a day, vacuum to waste, we then used yellow out and still had more of this dust.

Over the weeks the color changed from grey/white to yellow, then to brown. We took a sample out and looked under a microscope and it looked like sand, at least the brown stuff did. During this time we switched from cal-hypo to liquid shock because it was cheaper and easier to use.

I treated with a metal and scale remover to see if that was it and it didn't seem to do much. Eventually the problem seemed to get better. Except I can't keep my Ph and alkalinity stable.

We added a second return line to improve circulation. We then treated for phosphates because that number skyrocketed after use of the metal and scale remover, phosphates are still high.

Our water was perfectly clear this week, we concluded after microscoping samples it was likely dirt the last couple of weeks from construction in the area.

We did an OCLT and we lost 0 chlorine overnight last weekend. I shocked using liquid shock on Sunday and had no issues in the pool, got up to 18 ppm, no sediment. I used cal-hypo granular last night and ended up with the grey/white sediment in the bottom of the pool again. We looked under the microscope, it looked like sand again, this time in the water there was a white powder.

Is my entire problem due to the cal-hypo shock? Is this a common problem for it to do this if circulation in your pool isn't perfect? I do dissolve in warm water before putting in the pool but obviously it doesn't dissolve 100%.

Is the liquid shock not strong enough to kill algae if algae is my problem?

Secondly, what will cause Ph to constantly increase? My thought is we have aeration happening somewhere in our lines.

This entire time my pool has been balanced perfectly and water has been crystal clear.

Most Recent Chemistry:
FC:5.5
CC:0, stayed at 0 all week even with automatic chlorinator off
CYA:43
Alk:109
Cal:200
Ph:7.6
Phos:5700
Iron:0
Copper:0.1

 

[Texas Splash]

Welcome to TFP! You might be seeing some residual product form the cal-hypo settling. Liquid chlorine is our preferred method to chlorinate for non-salt pools and is plenty strong enough if the batch is somewhat fresh. Remember your pH will show higher whenever the FC is over 10.

The big question though ..... your signature shows a K-2005 with FAS-DPD, so why are you going to the pool store? Those test results above can't be from you, and we really hesitate to give chemistry advice from pool store results. Can you confirm your own test kit results?

 

[EmEeTee]

Will it usually continue to rise? That's been my issue. I bring it down and it is rising .4 or more every day. By morning I'm usually 7.8 or higher.

I posted a combination of my results from last night with the pool store's results from Thursday. Typically we don't go into the pool store but can't test our metal or phosphate levels at home. My home kit says my alkalinity is at 100, which is down from 130 that it was.

And let's be honest, the taylor kit is not that accurate in testing CYA levels. Initially when this began, our CYA was around 80 according to our kit, we drained half our pool to install the new return line and refilled. When I test at home, it's all subject to light and what a disappearing black dot means, so maybe you can explain, but my test this morning was 35ish.

Is there a benefit of getting your liquid from a pool store vs. Menards or somewhere else?

 

[Texas Splash]

My home kit says my alkalinity is at 100, which is down from 130 that it was.

That's a good start. Continue to lower the TA to about 50-60 and your pH rise should slow down. Once the pH hits 8.0, use enough acids to lower the pH to 7.2 and that will help lower the TA.

Is there a benefit of getting your liquid from a pool store vs. Menards or somewhere else?

It's all about availability, cost, and strength. Get the freshest chlorine wherever you can, when you can, and at the best price.

And let's be honest, the taylor kit is not that accurate in testing CYA levels.

It is one of the more challenging. Based on your latest test, just consider your CYA 40. Refer to the note below for future testing if it helps.

CYA Testing:
Proper lighting is critical for the CYA test, so you want to test for CYA outside on a bright sunny day. Taylor recommends standing outside with your back to the sun and the view tube in the shade of your body. Use the mixing bottle to combine/gently mix the required amounts of pool water and R-0013 reagent, let sit for 30 seconds, then gently mix again. Then, while holding the skinny tube with the black dot at waist level, begin squirting the mixed solution into the skinny tube. Watch the black dot until it completely disappears. If it helps, pour a little, look away, then look back and pour some more. Some people like to squirt enough solution to go line-by-line for a better feel. Once it disappears, record the CYA reading. After the first test, you can pour the mixed solution from the skinny view tube back to the mixing bottle, shake, and do the same test a second, third, or fourth time to instill consistency in your technique, become more comfortable with the testing, and validate the CYA reading. If you are still questioning your own results, have a friend or two do the same test 2-3 times. Share your results only after everyone is done to see if you came up with the same average results.

 

[Donldson]

And let's be honest, the taylor kit is not that accurate in testing CYA levels

You're confusing your terms. It is extremely accurate, it is just not very precise. That's compared to test strips which are neither accurate nor precise, or digital testing which is not accurate but are precise.

Unfortunately there's nothing readily available to test CYA accurately and precisely, so the melamine test is the most accurate option available.