gravity hot water controls

[mbrad]

hi all,
a mate of mine has moved into a property and asked me how he gets hot water without having the heating on. the heating is fully pumped and the boiler is piped up to accomodate the gravity hot water.
i have never come across this system before and would like some advice from someone who is experienced with this heating/hot water system. can any contols be added or shall i just make the whole system fully pumped? although i doubt my mate wants to pay for that.
any help would be greatly appreciated cheers

 

[seco services]

i would go fully pumped.
but surely the system has a programmer now that controls hw or hw/heating ?

 

[onlyfitidealboilers]

1,fit an anti gravity vlv on the flow for htg
2,fit a 2 port on the hot water circs after the open vent (c plan)