Hi, ponfie, and welcome to the Envirolink. I had Terraform construction in 1994-5 and designed greywater systems and rainwater catchment systems and combos. My Earthship takes roof rainwater in covered gutters to a pair of 4" ABS foam covered through the top tire course. It goes into a 425 gallon recycled pickup truck water tank on a platform 2' up I designed for it. It has a big hose coming out the cabinet for quick filling of 3 gallon waterers. Near the top intake is a 2 1/4" overflow caulked in to the hole drilled through the polypropylene tank. This goes to a floor drain and to out at the top of a rock pit using flex 3" drain, and a screen to prevent bugs and critters getting in. There is also the initial regular trap. There are screens in the gutter outlets, and at the tank top. A 12 VDC Shurflow pump takes water out of a 1/2" polypropylene line drilled in through the top, a screen on the end and internal stretched metal clothes hanger for rigidity. The poly switches to red copper as it goes under the floor to a T and total filter for drinking water in a vanity, then to the front main garden with drip lines. The electric is two 350 Ah 6VDC hooked in series as 12VDC, direct through a switch to the pump and also to a 300 Watt sinewave inverter and three CF lights and three outlets, for a small TV or guitar amps. The copper water line is ground.
The greywater systems I designed needed two large tanks--one below floor level with an overflow to a blackwater septic tank. Toilet tank type activators would turn on/off a Shurflow to pump grey water through a sand filter to and upper tank. The upper tank could gravity feed interior gardens, and go through another more powerful pump to 20 micron, 10 micron, 5 micron and 2 micron filters, a charcoal filter and under an ultraviolet solar powered (120VAC from inverter, batteries, charge control and solar panel/wind generator) to a pressure tank. Note that code requires not using this household grey water outside, and over flow to a black water system(pathogens can be transferred to someone in your yard, even with no trespassing signs). Basically two drain systems, with "Y' valves, etc. A 1500 sq. ft. roof in an area of 15" rain per year and 2-2500 gallon tanks could meet the water needs of a family of three, except in a drought where water would have to be bought. The grey water grows plants to eat, and a compost toilet with required black water overflow drain, and "Y's" to separate rinse water from initial dirty water which goes to the blackwater septic system. This is to save on cleaning the filters so often. The total greywater recycling systems must have their filters cleaned and replaced excessively and the whole system flushed too much, because of grease, detergent chemicals buildup, and pathogenic pollution buildup. I would suggest going to the library and studying up on plumbing. Avoid PVC--one pound vaporized can kill up to 400 grown men in 15 seconds or cause a thousand cases of a variety of cancers. It is not legal anymore for intake water, except a special sealed kind used in wells and septic drain/vent.
With ponds there are a variety of ways to get the water to the house holding tank, from solar/wind slow pumps to gas powered pumps used as necessary. Rainwater catchment must be from a non-toxic roof and may require some ingenuity. My roof is terra cotta colored acrylic.
Any more questions feel free to ask, knowledge without being spread is selfish.