Attached is a pdf regarding the construction of a 12v chemical pump cart. this can easily serve as a dual-purpose tool for window cleaning/power washing professionals.  You can use it to spray any desired chemical for cleaning various substrates, or as a draw pump or booster pump for your pure-water WFP setup.

Feel free to link to this page so your friends can build this sweet tool too!

12v Pump Cart for Chems_WFP – Google Docs