Past Perfect Continuous use

Past Perfect Continuous Tense is used in the following situations:

1. When we talk about a situation or an activity which took place before another event in the past.

The water had been boiling for half an hour before I noticed it.
It had been snowing the whole day and the children wanted to go skiing.

2. Past Perfect Continuous Tense is used in some conditionals.

If he had been working hard, he wouldn't have had any financial problems.

3. Past Continuous Tense is used in Reported Speech.

He said he had been working very hard.