Alex I would buy that product, Wayne described very well what is reqiured. This would be a winner.
IMO, and I know hardly any one agrees including you, but purified water hot delivery window washing will become the norm. There are lots of strategic reasons for this and an inevitablity, one of these is that it is idiot proof. Even I can't do a bad job.
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ps. had an explosion today, a little tip, don't put a hoselock end stop connector on the hot out- so nearly idiot proof. Blew a hole clean through the half inch connection hose to reel.