Help Needed. Off grid plumbing installation.

Hi all,
We bought a small plot of agricultural land with an agricultural building which we have refurbished into 2 flats  - one for hubby and me and one for our daughter. We have the bottom and she has the upper room.
The water source is a below ground cisterna that collects rainwater from the roofs.
I have acquired the sinks, basins and showers from freecycle etc and built the cabinets myself. There are no flushing loos, just basins, showers and sinks which will empty into a double reedbed before being used to water vegetation.
My plan is to install a 800W Sterwin pump - which has it's own water reservoir -on the roof of the ground floor bathroom. Pump the water up to that level and then into the upper storey flat, where it will be connected to a gas water heater to provide hot water feed, and supply cold water upstairs and downstairs.
Currently we are on a gravity fed system solely on the ground floor and previously I have cobbled together a basic gravity fed system from a 7 m high water reservoir. So I have no problems with the actual fitting of pipes, connections etc.
My query relates directly to the water pump, pressure, non return valves, gravity etc. Given that the cisterna is 2 m deep, the ground floor is 2.4m high, as is the top storey, how many one way valves do I need and where do I put them? I have attached a drawing - very rough- of where I plan to put the waterlines and the layout of the various basins etc. The kitchen and bathroom are back to back in both flats so there is only 1 water line on each level connecting all the water points.
I do hope the drawing is clear enough! There is a rough 3D version and a side profile which shows the split level.
I'm not convinced that the upstairs gas boiler is the best option for providing hot water downstairs. I am hoping to put some form of masonry wood stove downstairs with a coppercoil around the stove pipe feeding a thermosyphon tank affixed to the wall above the sink in the kitchen which could gravity feed the shower and basins in the winter, and switchover to using the sun to heat the water in the tank in our swelteringly hot summers when you can't use a woodstove indoors. But I don't think I can pull off a pressurised thermosyphon unit. Can thermosyphon work with a non-pressurised tank? This is a secondary concern though, my main aim is to get cold water from the cisterna to the upstairs flat, supply the upstairs with hot and cold running water and downstairs with cold water. I'm still happy to boil a kettle to wash dishes and shower with my 12V boat pump dumped in a bucket of warm water!

MY ANSWERS IN CAPITALS
My query relates directly to the water pump, pressure, non return valves, gravity etc.
Given that the cisterna is 2 m deep, the ground floor is 2.4m high, as is the top storey, how many one way valves do I need and where do I put them?
HJAVE YOU THOUGHT ABOUT A SUBMERSIBLE PUMP IN THE CISTERN WITH ONE NON RETURN VALVE AT THE PUMP?
I have attached a drawing - very rough- of where I plan to put the water lines and the layout of the various basins etc. The kitchen and bathroom are back to back in both flats so there is only 1 water line on each level connecting all the water points.
I WOULD RUN A LOOP FROM THE PUMP TO THE UPSTAIRS FLAT AND BACK DOWN TO THE LOWER FLAT SO THE PRESSURE DROP IS REDUCED OVER THE WHOLE SYSTEM.

I'm not convinced that the upstairs gas boiler is the best option for providing hot water downstairs.  WHY NOT?

I am hoping to put some form of masonry wood stove downstairs with a copper coil [I HAVE USED 1/2 COPPER PIPE, BYT 3/4 MAY BE BETTER ]
around the stove pipe feeding a thermosyphon tank affixed to the wall above the sink in the kitchen which could gravity feed the shower and basins in the winter, and switchover to using the sun to heat the water in the tank in our swelteringly hot summers when you can't use a woodstove indoors.
But I don't think I can pull off a pressurised thermosyphon unit.  NO THEY DO NOT WORK
Can thermosyphon work with a non-pressurised tank?  THAT IS HOW THEY WORK
This is a secondary concern though, my main aim is to get cold water from the cisterna to the upstairs flat, supply the upstairs with hot and cold running water and downstairs with cold water. I'm still happy to boil a kettle to wash dishes and shower with my 12V boat pump dumped in a bucket of warm water!

We could view your 7ft cistern as a shollow "well" and then from there build out like a regular house where:
Pump (with a single check valve)
Pressure tank
Then plumb inside the house as usual.

Hi John, thanks for your input and my apologies for not acknowledging your contribution-life got in the way of this project. I do have some follow up questions if you have the time to help? My questions  after your answers..

John C Daley wrote:MY ANSWERS IN CAPITALS
My query relates directly to the water pump, pressure, non return valves, gravity etc.
Given that the cisterna is 2 m deep, the ground floor is 2.4m high, as is the top storey, how many one way valves do I need and where do I put them?
HJAVE YOU THOUGHT ABOUT A SUBMERSIBLE PUMP IN THE CISTERN WITH ONE NON RETURN VALVE AT THE PUMP? I have the Sterwin pump already and my questions were related directly to where to situate one way valves and check valves in that scenario.
I have attached a drawing - very rough- of where I plan to put the water lines and the layout of the various basins etc. The kitchen and bathroom are back to back in both flats so there is only 1 water line on each level connecting all the water points.
I WOULD RUN A LOOP FROM THE PUMP TO THE UPSTAIRS FLAT AND BACK DOWN TO THE LOWER FLAT SO THE PRESSURE DROP IS REDUCED OVER THE WHOLE SYSTEM. As the pump is on the ground floor roof, I am thinking of a T joint coming out the pump.

I'm not convinced that the upstairs gas boiler is the best option for providing hot water downstairs.  WHY NOT? By the time the heated water reaches the downstairs shower I will have wasted at least 5L of cold water. Also each time I use the hot water tap I will be heating at least 5L of water which will cool in the pipes once I have switched off the water-that's quite a waste of gas. As I have plenty wood in winter and sun in summer, I'd rther use those energy sources as much as possible.

I am hoping to put some form of masonry wood stove downstairs with a copper coil [I HAVE USED 1/2 COPPER PIPE, BYT 3/4 MAY BE BETTER ]
around the stove pipe feeding a thermosyphon tank affixed to the wall above the sink in the kitchen which could gravity feed the shower and basins in the winter, and switchover to using the sun to heat the water in the tank in our swelteringly hot summers when you can't use a woodstove indoors.
But I don't think I can pull off a pressurised thermosyphon unit.  NO THEY DO NOT WORK So I can't use and old electric water heater/storage tank? I am trying to come up with a system that will switch between a solar collector and the copper coil by closing and opening relevant valves. And the system will have to be fed from the pump so my hot water would not be gravity fed either.
Can thermosyphon work with a non-pressurised tank?  THAT IS HOW THEY WORK Can you expand on the design?
This is a secondary concern though, my main aim is to get cold water from the cisterna to the upstairs flat, supply the upstairs with hot and cold running water and downstairs with cold water. I'm still happy to boil a kettle to wash dishes and shower with my 12V boat pump dumped in a bucket of warm water!

Hi Sarah,
I will start by saying that I am not a plumber, nor a plumbing expert... though I have messed around with it some as an amateur.

I can't imagine trying to plumb that many fixtures without a pressure tank. I think that a large pressure tank would make your life easier.

In theory, water comes to the pump, goes through a check valve, then through the pressure switch, then to the pressure tank. After that, the water gets split off between hot and cold water and then to the fixtures. So maybe, just 1 check valve in this situation?

I also came across this post. I only skimmed a couple responses, but it might have more information for you.

https://permies.com/t/175279/Don-put-check-valve-pump

Hi Matt, thanks for your prompt response. So far I have attached the main water feed from the cisterna (with a non-return valve at the bottom of the pipe through the sterwins pump. The pump has a lift capacity of 8m, 3800L/min and a psi of 4.3. I don't particularly want a highly pressurised system as we need to conserve water and my husband likes to leave taps running! I have connected the downtstairs bathroom basin and shower with separate feeds for hot and cold water -although I don't have a system providing hot water as yet. There is plenty pressure- I can run both basin and shower together without fully opening the taps. I still have to connect unstairs and the downstairs kitchen basin. So far I haven't used and check valves within the system. I skimmed that thread, I don't see anything that relates to my project but thanks for trying.

Stephen! Thank you for a well written, informative post that directly relates to my situation. I can easily retro fit the valves. As for the wood burning stove hot water, I have just completed my walker cookstove and am basking in it's warmth. I now have a year to figure out how to use it's chimney pipe to create a reliable thermo siphon non-pressurised  unit that I can potentially connect the inlet to my pressurised system and rely on gravity to supply downstairs hot water supply. Thanks for your help and the link.

Stephen! Thank you for a well written, informative post that directly relates to my situation. I can easily retro fit the valves. As for the wood burning stove hot water, I have just completed my walker cookstove and am basking in it's warmth. I now have a year to figure out how to use it's chimney pipe to create a reliable thermo siphon non-pressurised  unit that I can potentially connect the inlet to my pressurised system and rely on gravity to supply downstairs hot water supply. Thanks for your help and the link.

Water pressure in an interconnected plumbing system will depend on the pressure "accumulated" in a pressure tank or elevated tank, and elevation - those two things primarily. But it can also vary with flow - if a lot of water is being drawn near a source (like the pump when it is running, or a tank), the more distant points of use receive less pressure because the big use is creating pressure drop by flow friction. It is nice to have about 20psi/140kPa of pressure at a faucet as a minimum, and even three times higher is fine. That amount of pressure is equivalent to a static elevation change of about 30 feet/14 meters of elevation, so if you want nice pressure on the upper floor, an elevated tank has to be at least 14 meters higher than the upper floor to make pressure by gravity. If the pressure is derived from a pressure tank instead of by elevation, and the pressure tank is on the upper floor, then the tank pressure can be at least 140kPa and everything is fine. But if the pressure tank is on a lower floor, it needs higher pressure. Each meter of elevation change is about 10kPa, so if the tank is 5 meters lower in elevation than the upper floor shower, you need 190 kPa at the tank to have 140 kPa at the shower.

One way valves, check valves, do not have much effect on forward flow pressure. They are designed to let water flow freely in one direction. But they close if flow tries to reverse. In a typical house plumbing system, where the system is always above atmospheric pressure, the only reason flow would reverse is if the supply point ceased to have pressure. So there is generally only ONE check valve - at the supply. That can be a pump or other connection.

When a pump is set up at a cistern, and the pump is lifting water from above the water surface, the check valve is often placed at the bottom of the inlet pipe, and called a "foot valve". Most pumps are not designed for lifting water, but rather for pushing water. Even if the pump has "suction lift" that does not necessarily make it "self-priming" and even if it is self-priming, it generally won't be happy about it and you want to avoid making it a regular thing - which is why a foot valve is useful - it keeps the suction pipe full of water so self-priming is easier.

A pump will often be sold with a maximum flow rating and a maximum pressure rating. It is important to understand that the maximum flow occurs when the pump is not being required to deliver ANY pressure - it is wide open to atmosphere, and that the maximum pressure is the point where the pump is doing all it can to create pressure and so flow is essentially zero. It is tempting to think that a pump rated for "just enough" pressure will be good, but usually such a pump is very inefficient with power use. It can run a long time to deliver very little water.

House piping is often quite small - 1/2-inch or 10cm. This piping has a lot of friction, but it is cheap. House builders are all about cheap and not at all concerned about pressure drop, typically. But if you are building your own, spring for a little larger pipe and reduce down right at the points of use so you can still use "standard" connection fittings. The larger pipes don't cost much more and the pressure throughout the house will be much more steady. No warning the person in the shower when you are flushing the toilet. No sinks stopping flow when the washing machine is filling.

Thanks Cade for such an indepth insight into pressure and why it's important to plan from the start! I think I ended up going with 16mm pipes so hopefully have partailly addressed the pressure issue.