An 11L or 25L resin bottle already filled with resin and equipped with connectors (type Gardena) to attach hoses.

It can serve as a replacement for another resin bottle (swap) or simply as an extra resin bottle to filter water at home or in the van if needed.

No desire/time to go to the tap, not enough water at the customer’s site to continue working... then this is a fairly economical solution.