Is it necessary to shock a pool?

[Thatcher]

I am a relatively new pool owner & had the good fortune to stumble onto this site before I had any substantial issues & have been following most of the recommendations. I have a 23,000 gal in ground vinyl liner kidney shaped pool that I installed myself this spring. I followed my local pool store's startup instructions- and in hind sight did not do half bad- aside from being convinced I should raise the calcium.

My question-
Is it necessary to routinely (monthly or otherwise) "shock" a pool that has good chemistry? I actively test my chemistry (weekly, and more often during times of heavy rain) & do a good job of keeping my chemistry within the recommended levels. My Fc stays around 3.5 to 4, ph around 7.3, alk 110, ch 170, cya 45.

My equipment - hayward 1.5 hp variable speed pump which I run 1500 rpm constantly. I speed it up when the pool is in use to increase the chlorine levels. The filter is a hayward cartridge filter- not sure of the model, but 150 sq ft filter area. I also have a Pentair c320 chem feeder that is plumbed direct. I know they are bashed a lot on this site, but the c320 does not restrict the flow- the inside diameter of the feeder is 2" straight thru (I'm an engineer & spent quite a bit of time considering the fluid dynamics of the plumbing). The chem feeder seems to have no problem keeping up with the chlorine demand of the pool. The setting is generally low, but I turn it up after heavy rain or long periods of time with the cover off. I seem to be able to easily regulate the chlorine using the chem feeder with rather small swings in the chlorine levels. I mainly use trichlor pucks for the ease of use with the chem feeder , but I plan supplementing with the occasional use of bleach if my cya levels do get too high. I have also converted to borax and baking soda, but I typically only find myself adjusting the chlorine level and raising the ph (the acid rain in our area is constantly driving the ph down).

Do I need to worry about "shocking" the pool if I am testing routinely and successfully maintaining proper chemistry without it? Seems like every other pool related blurb I read, someone is discussing shocking their pool for one reason or another. Is there any best practice reason to be routinely shocking the pool just because? I was afraid I would end up with a trunk full of shock if I asked the pool dealer, but I would prefer not to be adding unnecessary chemicals.

[PoolDoc]

"Shocking" is a pool trade term with many conflicting definitions, but the common thread in most of them is that "shocking" involves quickly raising the free chlorine to a level 2x - 3x normal.

For most people, it's necessary because they are erratic in their pool treatment, and "shocking" can penetrate emerging algal biofilms before they become a serious problem.

One common misconception, which is artfully promoted by some pool chemical companies, is that "shocking" involves different chemicals than regularly treating with chlorine. It's true that trichlor is not a very practical 'shock', but all other forms of chlorine -- cal hypo, bleach, or dichlor -- are.

[Thatcher]

Thanks for the quick response.

One other question-
Are you aware of anyone making some form of chlorine tab that could be used in a chem feeder and does not contain stabilizer- or at least lower levels of it? Trichlor is ideal because of the convenience, but I'm sure I will eventually reach a point where I am forced to switch to bleach to avoid high cya levels. Seems like that would be a good opportunity for some chemical company to sell more pool products.

[Watermom]

Unfortunately, no. If there were, there would be a lot of people interested in using them, though.

[CarlD]

HtH and its sister company (PoolLife? or something) made a cal-hypo tab, first one in a plastic tubethat dissolved, then one without the tube.
The tubeless ones were pure garbage, becoming a pile of mush in less than a day. Never got hold of the tube ones but they were reputed to work much better.

But there are two caveats:
1) Cal-Hypo raises the calcium level in your pool so you have to stop using it at some point, plus it can be a bit alkaline, raising your pH
2) Never, ever put the tabs in a chlorinator or floater that had tri-chlor or di-chlor in it, and never let bleach touch cal-hypo! Very Dangerous!