"would have had to have been"!

English as a Second Language English Vocabulary, Grammar and Idioms
1

Hello.

Could you please explain the following sentence :-
The water concentration would have had to have been at least 5 ug/l? what is the tense of it?
can the following sentence be used instead:-
The water concentration would have to be 5 ug/l?

Many thanks

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2

It could develop like this: would have to be > would have to have been; would have had to be > would have had to have been. All very, very rare uses!

We can name and have 12 tense constructions in the normal course, as you know. This does not fall under any of them though it seems to have some link with the Type III conditional sentence.

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3
  1. Would have had = perfect conditional
  2. To have been = passive infinitive
  3. Would have to be = simple conditional

1 and 2 are quite different. 1 suggests the correct level was not reached and should have been. In other words 1 points to the past. 2 points to the potential and future requirement concerning the correct level.

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4

Hello, Sir Anglophile and Sir Alan
Thank you very much for your help. Because of your wonderful explanation, the meaning of the strange sentence became clear. So, it is a right sentence construction.
Many thanks

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