Also, have you tried testing for chlorine at night after sundown and in the morning before sunup to see if the chlorine consumption is only due to sunlight, (which would be the case if there's no chlorine drop at night but some during the daytime), or if there's still something in the pool that's consuming it, (which would be true if you're losing it at night when the sun isn't out)?

Keep in mind too, that the chlorine consumption will drop some as the water temp drops....

Janet