Quick question, when using mana recovery from effects such as flood valve or crawler, how much mana actually is left to use ? For example I had 8 mana and used crawler to recover morbid from mana tapped do i still left with 4 mana or 3 ? thanks for answering in advance

You will have 4

well that depends on how you tap your mana, it's wise to always tap the card you want to return from your mana zone, so in that case it's 4 like Halfar said, but you could be left with 3 mana if pick an untapped mana card.