Chlorine reading

[amin36]

Hi Guys

In one of the pools I am controlling there are some questions I encountered

The pools volume is 75 cubic meters

At first I was using sodium hypochlorite 15 % to chlorinate the pool, but later due to dilutions from the rain water which has the CH of 0 ppm I switched to calcium hypochlorite. Actually I checked the CH the last time and it was becoming 130 ppm and then I switched to Cal hypo to compensate the calcium loss of the water.

Now I came to understanding that in outdoor pools due to reduction of calcium hardness from dilution caused by the rain Cal hypo is the best choice

Do you agree my opinion?



And the second thing is:



that the last time I added CYA to pool water was 4 months ago.it was about 40 ppm then. we had dilution from rain and unfortunately I did not add CYA to pool water to compensate for the lost CYA.

For chlorinating this pool, I am using 6 small cal hypo tablets. I drop them into the skimmer and the temperature of the pool water is 13°c degrees.

Each time I test the amount of free chlorine it is always on 1 ppm even at noon time.

I can’t measure the exact amount of CYA with ordinary CYA test kits and I guess it must be zero due to dilutions from the rain water or it must be very low.

So, my question is:

Is this 1 ppm chlorine level because of the remaining CYA level which I don’t know what the amount is?

Or if my CYA level is zero because of constant dilutions due to rain, is it possible to have a 1 ppm free chlorine level even at noon time from cal hypo tablets only?



Ps: I attached a picture from the pool below



Thanks

 

[Texas Splash]

Remember that neither stabilizer (CYA) nor calcium get "diluted". They do however go down if you are required to remove excess water due to heavy rains (or if you have a leak). If your CH level is low (below 250 for example), then using cal-hypo tablets is fine, but I would not place them in the skimmer. Always use a tab floater. If your CYA is indeed low (below 30 ppm) then you must increase the CYA with stabilizer. A low CYA allows the chlorine to be exceptionally strong and also allows the sun to remove the free chlorine very fast. That could explain why your FC seems to fall so fast. If this has been an issue for a while, there is also a possibility algae is trying to grow which could also explain the excessive FC loss. To be sure, you could always perform an Overnight Chlorine Loss Test by using a test kit that accurately tests FC (i.e. TF-100 or Taylor K-2006C test kits). Hope that helps.

 

[amin36]

Thanks Texas Splash
but is it possible to have a 1 ppm free chlorine level even at noon time from cal hypo tablets only when there is no CYA ?

 

[Texas Splash]

is it possible to have a 1 ppm free chlorine level even at noon time from cal hypo tablets only when there is no CYA ?

Possible. Much depends on the amount of sunlight, but an FC of 1 ppm is of course much too low (algae).

 

[amin36]

I do not agree since the free chlorine is consistent with the amount of remainig cya therfore there will not be algae!

 

[Texas Splash]

I do not agree since the free chlorine is consistent with the amount of remainig cya therfore there will not be algae!

And exactly what method of testing and/or FC-to-CYA ratio are you using to support that statement? We at TFP are very clear about outdoor pools that require a "minimum" CYA of 30, and with that the FC should never be below 2, but ideally the FC should in in a range of 4-6 to prevent algae. With no CYA, any FC is eliminated extremely fast on a sunny day. Have you performed an Overnight Chlorine Loss Test to be sure?

 

[amin36]

Texas Splash​

I guess my CYA is around 10 ppm because i have a constent chlorine level even on totally sunny days around 1 ppm which does not reduce!
I mean i just cannot measure my CYA level with ordinary CYA test kits

Thanks

 

[Texas Splash]

I guess my CYA is around 10 ppm because i have a constent chlorine level even on totally sunny days around 1 ppm which does not reduce!
I mean i just cannot measure my CYA level with ordinary CYA test kits

In that case, it sounds as though limited/accurate testing is certainly your biggest challenge. An accurate CYA is very important so that we as pool owners know where the FC level should be. In places where it is cold and the winter sun angle is still low, FC can last longer. But in areas with a spring/summer sun that is higher and hotter over the pool, FC will fall must faster, especially if there is a low CYA. But that is why in the US we emphasize using a TF-100 or Taylor K-2006C for extremely accurate FC and CYA testing. We find those kits the most reliable, although there are a couple others that okay.