That harsh chlorine smell is almost never free chlorine. Here is what chloramines are, why they form, and the one-minute test that proves it.
Counter-intuitive but true: a strong chlorine smell almost always means there is not enough free chlorine, not too much. The smell is from chloramines, which form when chlorine combines with sweat, sun cream, and other organics. They irritate eyes and skin and are the chemistry telling you it needs help.
Free chlorine is the active sanitiser, the part that kills bacteria. Combined chlorine (chloramines) is what is left after chlorine has reacted with organics. Total chlorine is the sum of both.
If your free chlorine is 3 ppm and your total chlorine is 5 ppm, you have 2 ppm of chloramines. That is your smell. Anything above 0.5 ppm of combined chlorine warrants a shock.
Dose a non-chlorine shock at the bottle's per-litre rate, lift the cover, and run the jets for 20 minutes. The oxidiser breaks the chloramines back into nitrogen gas, which vents off rather than recombining.
Leave the cover off for at least an hour after, weather allowing. Closing it straight away traps the gases and the smell will still be there in the morning.
Test free chlorine and total chlorine in the morning. They should now be within 0.5 ppm of each other.
Shower before you get in. A 30-second rinse strips most of the body oils and lotions before they meet the chlorine.
Shock weekly even when nothing looks wrong. Chloramines build silently between sessions.
Keep your free chlorine in the 3 to 5 ppm band and your pH between 7.2 and 7.6. Outside that band, sanitiser fights itself and chloramines form faster.
After a non-chlorine shock, yes after 15 to 20 minutes once free chlorine has fallen back to the bathing band. After a chlorine shock, wait until the level is back below 5 ppm.
Not at typical hot tub levels, but it irritates the eyes and airways and is a clear sign the water is not where it should be. Treat the smell as feedback, not a feature.