Y'all do know that Celts get the credit for inventing soap?

Now, I do not know how often the Roman baths were drained and replenished with fresh water, but, all those guys sharing the same filthy water in the same tub isn't my idea of hygiene. The Celts could bath in streams, rivers, pools, etc...I see less of a chance to bath nasty water like this.

The only stone structures for retaining water that I know of off hand is an oval basin (reconstructed) from an Aedui town, Bibracte I think. Stone water channels were found as well for water flow. But no, these are not common feature in Celtic towns at all.