[jmclemore]

Get a pump operated keg and use your imagination when it comes to connecting it to a sink and faucet.

[Yo-Yo]

You don't want to pipe rainwater into the potable water system.

You could install a second gray water tank to capture shower runoff and rainwater to use to flush the toilet. That would reduce your total potable water consumption, but by the time you price out all the re-plumbing necessary you may be further ahead just sinking a well.

https://www.thenaturalhome.com/greywater/

[spokeshave2]

I'd need to add to screen out any roof sediment or other stuff that might gum up the pump.

I think you can install a bypass system on the roof down pipe...it sends to waste the first few gallons so the rest of the roof water is clean.

Called a "first flush diversion device"

[laker_dad]

How far down is the water table? Shallow wells (< 32 feet) are easy to put down.

[Governor Dinwiddie]

If you need more water, get yourself a rain barrel. You can get a nice 50 gallon rain
barrel with a brass spigot at Tractor Supply for $99. You'd be surprised how fast they fill.
Mine will fill in less than a half hour during most rain storms. If you need more
capacity, buy two.

[Sparticus]

I'd say that a 150 gallon tank is not going to cut it for a rental as the average American uses over 50 gallons a day. A half a dozen showers and the tank would be empty for sure. Also, how is the gray water handled currently? You could get a 1000 plus gallon tank, but I doubt if you could find one that would fit in the crawl space. I would expect to need to build a shed to house the tank and the pump. The next issue is how to keep it full. You could get a truck or trailer mounted tank to haul water, but that sounds like a lot of work.

www.watertanks.com/category/6/

[Pollard]

I lived off grid for 5-6 years and still currently don't have a well so I have some experience at this.

You can get those totes on craigslist all the time. Make sure you get one that had foodstuff in it. Don't take the seller's word for it. They have labels on them when their new and the labels last quite a while. They come in increments of 55 gallons with 275 gallons being most common. Preference is to have it in the winter sun and summer shade.

Those 12 vdc RV water pumps will lift 10-12 feet which means you can keep the pump indoors. Then you run an RV water hose from the pump inlet to the tank outlet. Run that hose through a piece of 6 inch insulated flex duct. Available at homedepot/lowes, it's typically used for HVAC. Attach/prop the outdoor end up against the tank leaving a small outlet for air to escape. Put a computer fan at the indoor end of the duct to blow warm air down the duct towards the tank, hence needing the gap/outlet to allow air to flow. I've used this in temps down to the high teens without it freezing. I also have an agricultural tank heater that keeps the tank water from freezing.

Forget the flush toilet or at least use an RV type toilet as they use a fraction of the water. Guys pee outdoors. Get a shut off to put at the shower head or get an RV shower head with a shut off. When you shower, get wet, turn water off, soap/scrub, turn water on to rinse, repeat for hair. You'll have to teach your renters this stuff.

[Hootowl99]

For the house that you're considering the incinerating toilet for, do NOT vent the flue vent into the crawl space as this is a radical risk of carbon monoxide poisoning to the prospective BnB customers. Follow manufacturer's specifications exactly for both the exhaust flue gas and combustion air. There's a reason why the manufactures sell flue kits for all this.

Essentially what you're setting up is a mini water distribution system to 3 nodes. I recommend that you engage a registered engineer to review your plans and if necessary revise them. I know this is private and all that but there are standards and if something screws up a customer could be harmed by water born bad things. Get a PE stamped design and you reduce your liability from design issues. Plus, there could be state or county permitting required for your distribution system and if so you'll need the stamped design for the application. For that matter, your insurance company may require a stamped design or even if they don't require this could give you a lower rate for having one.

For water supply needs, assume 35 gallons per day per person domestic use and 50 gallons per day per person surge capacity. This covers drinking, cooking, shower, washing and sanitary. The surge rate probably includes water for a nice little garden, which is actually the best use for rain water catchments. For the existing neighbors house you'd buy, DurRock would certainly be better than the plastic skirt. I have no idea if the increased heat retention would be sufficient to keep the water pipes from freezing. If it is not sufficient then a low cost way to get some heat into this space is to use a bus heater, which is cheap. Rig it up by moving its electrical stuff from the heater box to a separate NEMA 4 box for environmental and insect isolation. Get a relay and cheap temperature control to turn on/off the blower motor and a hot water pump that recycles water from the hot water heater in the house. You can probably get all this stuff from Grainger or McMaster. The blower motor is not going to be outdoor rated but will last awhile. When it does go out replace it with a TEFC motor. Again, this is Grainger supply stuff.

[Conan the Librarian]

Sailors use watermakers powered by solar panels. You just need a source of water to start with (sailors use salt water), run it through the machine, and, you have fresh water.

[LibWhacker]

I know this is a little late, but I just saw this thread.

Check this out. ...Just the results of a Google search. All kinds of information from all kinds of different people and sources. One of them has GOT to have a solution for your situation.