As with most DIY projects, this one was built in response to a problem.  Although now that I think about it a lot my projects create as many problems as they fix 🙂  I had a couple beers in a row that were great when they first went on tap but then after a few weeks would start to take on a buttery character that is typical of diacetyl.  Then, when a keg kicked I noticed around the edge of the beer post that a there was a bit of mold and a streak of dried beer that had run down the side of the keg.  After lots of research, I realized that half my kegs had the wrong posts (Type A instead of Type B (ie Cornelius)) and had been very slowly leaking.  I think what happened is the small beer leak had allowed a lacto or pedio infection to take hold in my beer lines which can cause Diacetyl.  Or maybe I’m crazy.  Anywho, I fixed all my keg posts but also realized my lines needed a very thorough cleaning.  So, I rigged up a recirculating keg line cleaner using a pool cover pump I use for my immersion chiller (which I hope to document soon).  Basically, I remove the tap I want to clean and take it apart, put the parts in a a standard 5 gallon bucket with 3 gallons of hot PBW solution (~140F which is my tap water at it’s hottest) and I then pump that using my pool cover pump up through the tap down through the keg line and back into the bucket.  This means it is in the reverse direction of how beer is served.  Pretty simple but works awesome.  After recirculating the PBW for 30 mins, I recirculate hot water for 10 mins to clean out the PBW.  Then just before putting my next beer on tap I run Star San through the lines to sanitize.  Since I started the new process, I have had no issues so maybe it worked or maybe its massive overkill!  My one concern is the hot water is not good for the pump, but I’ve been running the setup for a few months now without issue.  I guess time will tell.
Part List:
Qty 1  Little Giant PCP550 Pool Cover Pump $55
Qty 1 Hose Adapter $3
Qty 1 Tap Faucet Adapter $8
Qty 6 3/8 ID hose (ie 6 feet) $5
Qty 2 Hose Clamp $2
Here is a video of the setup running:

Here are the two connectors (left goes in the tap base and right is garden hose adapter that goes to pump):

Here is the pump connected to 3/8″ ID tubing that goes up to the tap base:

Here is a wide angle shot of the setup but with the pump out of the bucket.  Do not run the pump dry!

Here is the actual setup running.  Notice that the hose that runs from the keg up into the tap is feeding back into the bucket.

An aerial view of the bucket with everything running.