Yes, without sealing it, concrete is porous unless it's waterproof concrete, which was developed by the Romans over 2000 years ago--but it was very expensive then and still is today.

If you are not familiar with our techniques of pool chemistry, you really should read up on them. Most of the information out there for many years, and most of the ways most pool owners manage their pools, is wasteful, expensive, and sometimes not as effective. There are "rules" that are simply flat-out wrong, for example, that 3ppm is the maximum safe chlorine level. This is flatly untrue in more ways than you can imagine.

A number of our members, including Ben, the PoolDoc and site owner, are VERY experienced managing large, public pools like yours, but even we moderators and other posters know the chemistry SO well we can do the calculations.

Maybe you are familiar with our B-B-B method and T/A lowering methods, but if not, they may surprise you as they contradict much of what pool stores tell their customers.