This is how i did it, made this video after the Vegas round table 2009, I enjoy the DIY tech stuff.
Getting more gpm, was one of the things everyone seemed to want at a job site. Most of us started with a 4 gpm unit or had one as backup, so why not put it to use and speed up your job in the process.
The other thing that amazed me after I got my first hot water machine was the amount of waste heat from the boilers, and the amount of fuel need (and cost) to raise the temperature of water via these heaters.
I have been saying pre-heat for hot water pressure washers for a long time, then Landa does it with the ECOS, now aaladin pw , and Jerry says he has something in the works (maybe we will see it 2013). I would still like to work with a manufacturer or OEM on a project like this.
The other thing that really had me going is vacuum recovery and mobile filtration, have had some great/ and not so great times with this. If anyone need my opinions on systems directed at our pressure wash market and even other markets, you are welcome to give me a call. I still maintain that flocculation is an awesome method of mobile water treatment for reuse.
Anyway here is the how to video I did on joining to machines,
http://www.youtube.com/watch?v=02PkryqmatU