Cal hypo sediment?

[morzh]

As I told in "high chlorine" thread I shocked the pool with Cal hypo yesterday. (a turtle visited me so needed to sanitize).

To refresh, I have high CYA (95) so my chlorine is high and is 6.5ppm, not going anywhere though I stopped adding it.
I used three packs of 1lb of 76% of Cal hypo.
I ran the pump and broadcasted the most of it over the deep end, and very little over the shallower part.
While running the pump, after an hour though it was dark, I noticed sediment at the bottom.
I brushed it, ran the pump some more and eventually stopped it.

Today after work I saw a lot of sediment (large white crystals) on the pool floor. All over, especially in creases, but also lots on the flat part and the slopes.
I took the brush and gave the pool a good swish. After an hour or so very little came back, mostly in corners.

Why is it? I never had cal hypo not fully dissolve in my above ground that was nit even that deep.

 

[JoyfulNoise]

Do you have a full set of water test parameters from before adding the CalHypo? CalHypo is know to cause temporary water cloudiness from the formation of calcium carbonate. Depending on the condition of your water prior to adding the 3lbs of CalHypo, you could have easily scaled out calcium carbonate.


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[morzh]

My calcium was at about 180.
Fc=TC=6.6ppm.
pH=7.8-8.0
TA=110




I had no cloudiness. Most of the sediment after brushing disappeared, this morning a bit came back, I brushed it again..
It is not a problem (or I think it not to be) just want to know why.

 

[pooldv]

Chlorine of 6.5 is not high for cya of 95. The target level chlorine for CYA of 95 is 12. And it should never drop below the minimum of 7. Chlorine CYA Chart

PH needs to be kept between 7.2 and 7.8

 

[morzh]

Yes. And how does it explain the sediment?


As for the FC it stays put two days after I shocked and is where it was before the shock. In other words it barely dissipates and probably does not get spent. The min is 7 and 6.6 is pretty close, might be 7 in fact, I am guessing by the color as it is off the scale with max of 5. And --- I haven't added any in these 2.5 days.

 

[JoyfulNoise]

Without knowing more details about your pool, here's my best explanation -

The cal-hypo you use is a mixture of calcium hypochlorite, calcium hydroxide and some calcium carbonate. For every 10ppm of FC added by cal-hypo, you add 7ppm to CH. So, when you dump the powder into the water, you locally get very high pH and very high CH until the powder dissolves. This is why it is very advisable to brush vigorously when adding cal hypo to ensure good mixing. With locally high pH and CH, you get scaling of calcium carbonate that will, over time, be redissolved into the pool water but can look like sediment. This is why large doses of cal-hypo can often make water look very cloudy at first. Even if you try to dissolve an appreciable amount of cal-hypo in a 5 gallon pail, the resulting water mixture will look very milky.

 

[morzh]

Anything calcium looks murky when dissolved, and heats up too.
I had to add calcium before, predissolving it in a bucket, it was like milk and very hot.

 

[elwood58]

Yes. And how does it explain the sediment?


As for the FC it stays put two days after I shocked and is where it was before the shock. In other words it barely dissipates and probably does not get spent. The min is 7 and 6.6 is pretty close, might be 7 in fact, I am guessing by the color as it is off the scale with max of 5. And --- I haven't added any in these 2.5 days.

Please be very careful. The test you describe is for Total Chlorine, which includes FC and CC. If CC is present, your FC could be significantly lower than you think.

 

[morzh]

No, CC is not present. TC=FC, as I said.

 

[morzh]

Well, I solved it fairly simply for the remainder of it. I put the cleaner in yesterday in the evening and let it vacuum the whole thing. As it vacuumed, the thing being soluble, it probably mostly dissolved. There is no sediment anymore, the water is sparkling.

 

[chem geek]

Excellent. It will dissolve faster after getting sucked up into the bag and getting flow to it. Just sitting on the floor there is very little water flow unless you have a return pointed in that direction.

 

[morzh]

It was not a lot left but it is almost exponential process so every time I brushed portion of it would come back so the robot helped.

 

[duraleigh]

This thread is an example of making things more complicated than they really are. The answer was simple.....the Cal Hypo was undissolved.

Physical movement (circulating water around it via the robot) was all that was needed to get it dissolved and into the pool water as chlorine.

Obviously, I am in possession of 20-20 hindsight but we should take away a couple of things.

1. Always look for the simplest explanation.....it seems like it is most often the correct answer

2. None of the other chlorine products are as good as liquid chlorine......they all have side effects.

 

[morzh]

This is how it looks now (and has been since I opened it 4 weeks ago).