Sportwash will help strip detergent build-up from your diapers, I think that is what you are seeing.
When I first switched to Sportwash, the first three or four washes were full of suds, even though I rinsed several times for each load. I was discouraged until I posted like you and had several Sportwash users report the same phenomenon. But eventually the suds stopped.
I still do have lots of suds when a non-diapering item sneaks into the diaper pail. I used to wash things like night-peed pajamas with diapers, but since I still use regular detergent on my other laundry, I get lots of suds. So now I wash everything separately. I am seriously considering switching to Sportwash for all my laundry.
HTH!