Counter flow chiller sanitation

[collar_builder]

I have a duda diesel counter flow chiller. On my last brew I did a back flush to clean it, but some water remained in the chiller. Now I'm worried that something could be culturing in there that I can't clean out.

Any ideas on how to be reasonably certain there is nothing growing in it?

 

[microbusbrewery]

Soak it in PBW to clean it, then flush it with hot water, then boil it.