There is nothing wrong with a homemade system. If it's making you money then it's serving it's purpose. If you're spraying from the ladder, you'll definitely want at least a 7+ GPM pump with a consistent "open" PSI of 60 or more. To achieve those results I recommend the Flojet R7300132A. A 5 GPM pump will work as well, however, they usually produce a "open" PSI of about 40 which will limit your distance. You can also try changing your spray nozzles; a 0050 works really good for distance.
More than likely, the Fat Boy relays keep blowing because of incorrect wiring. Make sure that all leads are at least 10 AWG and no longer than 16 - 18 inches from the battery. Also, if the batteries are not fully charged, it will cause additional stress on the pump causing it to overheat and fail. As far as the leaks, you always want to make sure you are using the correct fittings and sealant.
Since you only complete one or so roof cleanings a week, I would not invest a lot of money into a new build. However, if you are interested in spending the money, we do offer a great system for around $5,000.00.
If I was you, I would spend $600 - $800 and build your own system using all the correct stuff and you won't have any problems.
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