check valve in boiler output

I think use of check valve here is to avoid any condensate flow back to boiler. Just imagine when you get condensate hammering in main header. What can you do to avoid back flow of condensate (during condensate hammering, its like bullet) ??You must use check valve even if any code dont demand. will give u more info

its impossible, because all condensate will remove after trap and in trap set we have check valve.
this is not for condensate return,