River bet sizing

[corsakh]

Villain is 20/10/2 type regular. Fairly passive.

220BB deep.

I raise 99 UTG, he calls OTB, BB calls.

Flop 567r.
I bet $5 into $6. He calls. BB folds.

Turn A.
I go for a bluff. $11 into $16. He calls.

River 8. Pot is $38. Backdoor flush.
Hero ???

[ghostface]

22

[2p2J]

$20-25 looks perfect here maybe even more. He wont put you on a flush most likely. If he has an ace or aces up he would likely call 30...

[losingdonkey]

I bet 30 but I'm greedy

[Hail Eris]

Bet a lot. Like $30+. He'll have 88/44 a lot, and won't call a 3rd barrel with much else anyway.