We have gravity fed water with a 2000L header tank at about 3 meter head, the water flow is a bit slow but we don't need to run a water pump constantly(which wastes power and is noisy). We have a copper tank that is hooked up to a combustion stove to heat it up.
The water thermosyphens to the hot water tank which we have wrapped in at least a foot of wool that is stuffed into a sleeve made of shade cloth. This means that the water will stay hot for at least 24 hours(in 5degree weather) and is still warm after 2 days, the more hot water you use the less the time it will stay warm for though. We have also made lagging for some of the pipes by taking a raw sheep fleece and wrapping around the copper pipe and then using duct tape to hold the sheep wool in place.
We have only had the setup running over winter, and we are looking at backing it up with solar hot water over the summer. We are currently looking for a solar hot water panel or tubes. We also are finding it difficult to just locate a panel by itself without pressure relief valves and pumps etc. The only requirement for it is that the pipes are a big enough diameter. Our combustion stove works well with only 3/4" so that should be fine for the SHW.
I'll try and explain how we have hooked up our system below (hopefully it makes sense)
- Copper tank with 4 entry points, one at the bottom (on the side), one a 1/3 of the way up and one at 2/3 (both these are on the opposite side to the bottom entry point) and one at the very top centre of the domed tank
- Combustion stove with 2 entry point, one top and one bottom (these come out the back of the stove).
- a small feed tank with ball valve, with 2 entry points, one into the valve and one at the bottom, it also has an overflow outlet.
Location of components:
- Small feed tank is above copper tank on roof, it has an overflow outlet onto the roof
- Copper tank is below small feed tank in the roof space
- Combustion stove is in kitchen as close to below copper tank as possible
How it is connected:
- From cold water header tank to cold water taps, this is also connected to the ball valve in the small feed tank (we have 1/2" but 3/4 pipe would probably be better)
- From the bottom of the feed tank 3/4" pipe is run down to the bottom entry point of the copper tank, this is the cold water inlet for the hot water system.
- The 1/3 entry point from the copper tank is connected to the bottom entry point in the combustion stove, this should be 3/4" or bigger. This pipe should not go above the copper tank entry point and should rise all the way from the stove to the copper.
- The 2/3 entry point from the copper tank is connected to the top entry point in the combustion stove. This should be 3/4 or bigger and should not go above the 2/3 entry point and should also rise all the way from the stove to the copper. This is the hot water return, this pipe will get hot first, the 1/3 pipe will get hot once the copper tank has at least 2/3rd hot water in it.
- The top copper tank entry point is the hot water outlet and can be 1/2" pipe to all the hot water taps in the house (the bigger the better the flow, but it should not be bigger than the inlet pipe). This exit also has a tee connector that has a vent pipe come out through the roof(they are usually bent into a hook) and it can either drip onto the roof or go into the feed tank. This is very important as it makes sure that you do not pressurise the copper tank and cause it to explode.
You don't need the small feed tank with ball valve if the vent pipe is above the water level in the cold water header tank or can be fed back into your cold water header tank, otherwise if the vent pipe is below then the water in the header tank will gravity feed out the vent pipe!
This setup is quite simple and means that you don't have to worry about high pressure and pumps etc. We put it together in about 2 days and I am no plumber(I did look at similar system setups and talk to quite a few people about it before putting it together though).
To add in the SHW it would have to be plumbed up so that the entry/exit points are below the 1/3 copper tank entry point, and would have to be careful so that the thermosyphen does not draw the water through both the SHW and combustion stove. So they would be connected in parrallel not series which allows for separate loops.
Let me know if this makes sense, if not I can probably draw something up and post a picture
Living off-grid and loving it!