Should I empty some of the water out of my pool after heavy rain?
Water is a precious commodity so you should avoid emptying water out unless it is absolutely necessary. In general, it is better to let the water overflow rather than draining it out. That way you conserve as much of the water (and chemicals!) as possible.
Consider the following:
If the pool overflows, where will the water flow? Is there anything that may be damaged by the water overflowing?
If the overflowing water is likely to cause flooding or damage anything then you should empty some water to avoid this. If the pool has been well-built it should have adequate drainage in the surrounding area to avoid flooding. Be sure to check that storm water drains are cleared of any debris so that water can drain.
Also consider what effect the diluted chemicals may have on surrounding areas
Is there more rain predicted?
If there is a high chance of a lot more rain it may be worthwhile draining some water in advance. Try to leave this until you are completely certain that there will be rain to avoid wasting water or chemicals unnecessarily.
If you let the water overflow, rather than draining it, you will lose less chemicals.
When you leave the water to overflow it is losing the water when the chemicals are the most diluted. This means you lose less and save yourself money replacing them. Remember that some chemicals do not evaporate with the water so try to leave the water to evaporate rather than dumping it.