Cleaning copper

So I made this copper sparge arm with lots of fittings and solder that looks really good but is probably way too over-thought to be effective ;D An any rate, what would be a good way to clean it (internally) to remove the flux hiding inside? Would PBW do the trick or is there a better way to clean the inside?

Many fluxes are water soluble, but some require alcohol. Older rosin flux required alcohol, but it isn’t used much anymore that I know of. I assume you used lead free solder.

Acid #5 work very well

Lead free solder and flux.

Where might I find acid #5 and what is it?

I recently had a new HVAC put in my house and had them leave me the 3/4" copper tubing going to the old outside unit. Looks like there is oil on the inside. would this Acid#5 work for that? Was thinking about making a wort chiller with this.

Are you thinking IC or CF? if IC then you don’t really need to clean the inside but if you want to you can just run hot soapy water through it. or PBW. If a CF then you will need to clean it very well. I would think PBW would take care of it but if not white vinegar probably would, just rinse really well.