Are you wondering how coffee carts and caterers make mobile espresso work? Then it's time to learn about Flojet pumps and accumulator tanks!
The BW5000 is the most popular model (and it's available from a wide variety of sources) for drawing water from a 5 gallon jug or other container into an espresso machine. An Accumulator tank is also an increasingly recommended tool for more consistent performance and decreasing wear and tear on the Flojet.
This video does a great job of showing how these pieces fit together and work. Clive doesn't stock these items yet, but they are easily available and super simple to setup because they use hard plastic hoses and quick connect fittings (you may need to change the fitting on the accumulator to fit the Flojet or other brands of pumps). The Flojet's plastic tubing is 1/4" diameter, so you'll likely need to replace the inlet fitting on either your accumulator or espresso machine hose with a 3/8" or 1/4" John Guest style fitting.
This is how home enthusiasts and carts have made plumbed machines work for many years, and google searching “espresso accumulator tank” or “espresso flojet pump” will show you a lot of threads about how people have made this fit in their space.