Effectiveness of granular chlorine vs granular algaecide?

[socalpoolguy]

Anyone here, especially Chemgeek that could tell me the pro's and con's of using either of these 2 products:
1. http://oreqcorp.com/treatment/algaecides/index.asp ---the granular form, http://www.oreqcorp.com/msds/english/PD ... AECURE.pdf --here's a MATERIAL SAFETY DATA SHEET
This one is the Trichlor.

2. http://oreqcorp.com/treatment/sanitizers/index.asp ---the granular form as well, http://www.oreqcorp.com/msds/english/PD ... ANULAR.pdf ---here's a MATERIAL SAFETY DATA SHEET
This one is the Dichlor

I was told to use the granular Trichlor over the Dichlor for the purposes below:

My main question is, is using either of these products better than using liquid chlorine alone for maintenance? I understand that using the granular forms also adds some cyanuric to the pool, but any idea how much in 1lb of the granular gets added to the pool?
I'm trying to determine if using the granular for 1 month (using 1 or 2lbs a month per pool in the Winter/Fall... and 4lbs a month in the Summer, in San Diego), and then, using liquid chlorine for 2 months and repeating that cycle is a good way of maintaing pools? Hopefully that makes sense, any thoughts or advice would be greatly appreciated. Thanks.

 

[bk406]

Richard can give you the weight equivalents, but:

For every 10 ppm trichlor you add, you are adding 6 ppm CYA

For every 10 ppm dichlor you add, you will add 9 ppm CYA

 

[JasonLion]

In most cases it is not so good to use either of those products on a regular basis, though there can be exceptions.

Both dichlor and trichlor add chlorine, add CYA, and lower the PH. Dichlor adds 0.9 ppm of CYA for each 1 ppm of chlorine. Trichlor adds 0.6 ppm of CYA for each 1 ppm of chlorine. A typical pool uses around 2 ppm of chlorine a day, so over 1 month you would be adding 36 ppm or 55 ppm of CYA. Doing that for one month is usually alright, but doing it for a couple of months is rather likely to cause problems. The constant reduction in PH can also be an issue, requiring frequent additions of soda ash, or something similar, to raise the PH back up.

There are some pools where there is a high enough rate of water replacement, most likely through some combination of backwashing, splashout, rain overflow, etc, that CYA levels do not accumulate too quickly. This is however rare.

 

[chem geek]

I think that the info above including the amount of CYA relative to the amount of FC is most useful, but if you really want weight equivalents then one pound of Trichlor has the equivalent of 8.9 ounces (0.56 pounds) CYA while one pound of Dichlor has the equivalent of 8.1 ounces (0.50 pounds) CYA. However, you have to use a greater weight of Dichlor to get the same FC relative to the weight you need for Trichlor which is why Dichlor increases CYA faster over time given the same chlorine demand. As noted above, CYA can build up quickly over months if you don't have significant water dilution.