I would 1. Cold water from tap. Open to drain. 2. Warm water from tap. Open to drain. Now all dirt you can see is gone. 3. Circulate caustic or dishwasher detergent to get what you can't see. Warm. Can be reused for the small stuff later. 4. Warm water rinse. 5. Cold water rinse with acid. Starsan. 6. Rinse if neccesary.
Why not just take the elbow off the bottom under the sight glass and place the bucket under that. You can soak the elbow and butterfly valve with the parts you mentioned later. Then no need to worry about return. It should all dump out of the bottom as fast as it's pumping it back through. Just mentioning it because that is how I do it and works well. I just leave it run and forget about it for an hour.
No concerns of your pump getting clogged with all that nastiness coming out? Seems like you'd need to do a quick manual clean first, then run the PBW cycle. I hesitate to believe it can really get clean when it's recirculating that totally filthy water.
metaltim I Know right. But it really does get that clean with that warm PBW cycle. It does get a warm clean water rinse after and then a a Sani Clean cycle after that. The only gunk issue is that some larger chunks do get stuck in the spray ball from time to time and has to be backflushed.
