As you know "shocking" to get your chlorine levels up is touchy business, but here is a good idea and much easier for you to do:
Non-chlorine shock -- most notably potassium monopersulfate. This shocks the water in their pools in a more safe and effective manner. You don't have to wait for combined clorine readings to rise above proper levels, companies are using monopersulfates on a regular basis as a preventative measure to oxidize contaminants before they combine to cause water quality problems.
In addition to potassium monopersulfate, other oxygen-based shocking chemicals could include sodium persulfate, sodium carbonate peroxyhydrate (aka sodium percarbonate) and hydrogen peroxide. Sodium persulfate has about the same active oxygen content as potassium monopersulfate, but has a low reactivity and also can cause the chemical buildup in indoor pools. The other two have high active oxygen content and are commonly used in dechlorination.
The advantages of oxidation without clorine include the fact that there is no added production of chloramines and sanitizer efficiency is increased without raising the chlorine level. The chlorine without its added dut as an oxidizer is free to do its job as a bacteria killer. At the same time, monopersulfates accelerate chloramine degradation.
With regular, preventative use, you end up with better water quality, longer periods of uninterrupted swim time, and a more manageable maintenance schedule.
Potassium monopersulfate is a strong, odorless, oxygen-based oxidizer that works well with sanitized chlorine, bromine and most alternatives. Unaffected by UV degradation, non-chlorine shock can be added to pool water day or night, and swimming can resume after just a short waiting period.
The product is fast dissolving, and when broadcast uniformly over the water with circulation system running, it will quickly mix into solution with the pool water. Because of its characteristics monopersulfates will not damage or face vinyle liners.
Recommended doses are one pound per 10,000 gallons of pool water, but more frequent and higher doses may be useful in commercial pool applications. In spas, manufactuerers recommend oxidizing with non-chlorine shock after each use. Recommended dosage for spas is 1 - 2 ounces per 250 gallons.
DuPont, the manufacturer of potassium monopersulfate, recomments its use on a regular basis rather than waiting for problems to occur. Their reasoning is simple: If the condition of your pool water is so bad that it needs shocking, something has already gone amiss and you don't have to be a chemist to know that it makes more sense to prevent a problem in the first place than it does to try to fix one once it has occurred.