Ummm, No i think. None of the system is pressurised. Water is pumped from the tank to the collectors and gravity returns it. All that is required is the pump intake must stay submerged at all times.
The only exchanger required is a double walled one for the domestic hot water. all the remaining water is used directly.
If you really intend to space heat as well as domestic then you want to consider some form of dump load for the summer. Pool heating is a good way to go if you have the option.
I have a diagram but no way to post it....
Two manifolds - supply and return with a valved bypass between them for servicing.
water from the collectors is pumped backwards through the system from the return to the supply side.
each circuit has a separate pump and check valve.
