Shock/ Dichlor Vs Cal Hypo

[JFS]

I was switching to calcium hypo for shock treatmewnt and wondering if there is something to be made aware of. I have always used dichlor and have been having prob with cya running a little high, I also use dichlor tablets. The first time I used dichlor, they failed to tell me it could eliminate chlorine levels in my pool, I just wanted to know if hypo will have any effect on chlorine or ph.

Thanks

[chem geek]

I think you meant "trichlor tablets". Dichlor for shocking is generally a no-no because it increases the Cyanuric Acid level. The following are chemical rules of fact that are independent of product concentration and size of pool.

For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.

For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.

For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by 7 ppm.

Some simple math shows that even with a low 1 ppm FC per day chlorine usage, Trichlor will increases CYA by over 100 ppm in 6 months if there is no water dilution. Dichlor increases the CYA even higher. Cal-Hypo will increase the CH, but since that can be a higher level, it may be OK for a while in your pool.

Chlorinating liquid or bleach do not increase neither CYA nor CH. Though they increase salt twice as fast (all chlorine sources increase salt), the salt level can be far, far higher than either CYA or CH so it takes far less dilution (backwashing, splash-out, rain overflow) to control.

If you were to properly maintain your FC level relative to your CYA level, then you would not need to regularly shock your pool at all. Read the Pool School for more details.

[quantumchromodynamics]

The first time I used dichlor, they failed to tell me it could eliminate chlorine levels in my pool, I just wanted to know if hypo will have any effect on chlorine or ph.

Thanks

What do you mean that the dichlor eliminated chlorine levels in your pool? Dichlor adds chlorine, it doesn't eliminate it.

[chem geek]

I think he means that they didn't tell him that it would increase CYA thereby reducing chlorine's effectiveness. As you point out, it does increase chlorine levels, but it increases CYA by almost as much as FC so for shocking it can make matters worse. JFS, Dichlor does not eliminate chlorine levels.

[JFS]

I think you meant "trichlor tablets". Dichlor for shocking is generally a no-no because it increases the Cyanuric Acid level. The following are chemical rules of fact that are independent of product concentration and size of pool.

For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.

For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.

For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by 7 ppm.

Some simple math shows that even with a low 1 ppm FC per day chlorine usage, Trichlor will increases CYA by over 100 ppm in 6 months if there is no water dilution. Dichlor increases the CYA even higher. Cal-Hypo will increase the CH, but since that can be a higher level, it may be OK for a while in your pool.

Chlorinating liquid or bleach do not increase neither CYA nor CH. Though they increase salt twice as fast (all chlorine sources increase salt), the salt level can be far, far higher than either CYA or CH so it takes far less dilution (backwashing, splash-out, rain overflow) to control.

If you were to properly maintain your FC level relative to your CYA level, then you would not need to regularly shock your pool at all. Read the Pool School for more details.

On the package from home depot which I have been using for years it says "4-in-1

Shock" sodiium dichloro-s-triazinetrione 58.2%.

I beleive I made a mistake about lowering chlorine levels that was a result of using a product called "No Mor Problems"

Thanks for everyones responses-Joe

[chem geek]

No Mor Problems (as shown here) is sodium bromide. This does indeed consume chlorine and in fact turns your pool into a bromine pool. Bromine isn't protected by CYA so will break down in sunlight, though not a quickly as chlorine with no CYA. So yes, your chlorine demand will increase when you use this product -- it increases a lot when you add the product and then continues to be high (though not as high as when dosing with No Mor Problems) until the bromine eventually after a long period of time dissipate (outgasses).

The main reason that a product like No Mor Problems works is that it gets around high CYA level by moving all of the chlorine into bromine where bromine is not moderated in its strength by CYA. This is a similar approach to using ammonium sulfate in a pool to intentionally produce monochloramine to fight algae where the chlorine gets converted to monochloramine with the latter not getting moderated in strength by CYA. These are not good ideas. The right approach is to get to the source of the problem which is the high CYA level itself. Lower the CYA via dilution and keep it low by not overusing stabilized chlorine (i.e. use unstabilized chlorine as your primary source of chlorine).

Richard

[JFS]

I think he means that they didn't tell him that it would increase CYA thereby reducing chlorine's effectiveness. As you point out, it does increase chlorine levels, but it increases CYA by almost as much as FC so for shocking it can make matters worse. JFS, Dichlor does not eliminate chlorine levels.

I added the calcium hypo, only one bag, and both my PH and Total Chlorine shot up. Is this normal?