You asked for specific recommendations on what and where to buy and, I'm sorry I don't have that. I do have some experience with water filtration and I'll share my thoughts. If you've been doing research and looking at products, then you've already noticed that a lot of these products look like they were built with an Erector Set. There's no rocket science here. Just about everyone out there is simply buying off the shelf filter canisters and pumps and slapping together a metal frame to hold it all. It's so easy to get into this business that most of the companies you find will be here today and gone tomorrow. So the first thing you need to make sure is that the filter cartridges are widely available from vendors other than the one you bought your filter system from. The next thing to think about is how much you want to spend. 300GPD puts you in the light commercial range and there is a wide range of products available. On the cheap end you have stuff that is as cheap as the mid $250 range. It's that cheap because they used the smallest filters possible, used cheap PARGRIP style fittings (or worse yet, press fit fittings), and the support/mounting hardware is minimal. That system will be taxed to keep up with its 300GPD rating and you'll be changing filters frequently. At the other end of the spectrum there are systems that cost $1,100 or more. They have larger filter cartridges, solid threaded fittings and tubing, a robust frame, and extensive pressure monitoring. Maybe the sweet spot is in the middle somewhere.
Remember, at this level, the systems typically don't include a tank. For what you're trying to do you're going to need a BIG tank. A 300GPD system will kick out about 12 GPH. So you'll need around 10 hours to fill the tank in your van. Systems like this are typically paired with a 15 - 20 gallon tank which does you no good at all. You would probably be best served by plumbing the RO directly to the tank in your van. In theory, a 300GPD system would roughly fill your 125 gallon tank over night.
I don't know how much you know about RO systems so I'll throw in this next bit just in case you aren't familiar. A well designed RO system will send about 4 gallons of "waste water" down the drain for every gallon it produces. So if you're currently burning through 100 gallons of water each day, the RO system will take that up to 500 gallons of water per day. Only you can tell if that's going to have a big impact on your water bill.
That last thought brings me to an area that I don't have a lot of experience with. Your application will have the filter running somewhere between a 50% and 100% duty cycle. These systems aren't designed with that sort of use in mind. Like I said before, they are typically paired with 20 gallon tanks so that assumes about 2 hours of operation to fill the tank and then some extended period before the filter restarts. The filter cartridges shouldn't care. But the life span of any pump will be shortened if they are run at high duty cycles. That's a subject you would take up with the manufacturer.
I'm curious why you want to go the RO route instead of using an ion exchange softener which, depending on your water content, would yield the spotless results you desire with likely lower operation costs.
Bill
