Whether it be a new installation or your iStore has been installed for some time there are a number of factors to consider.
NEW INSTALLATION:-
All appliances and fittings within an Australian home are now produced to accept a maximum pressure of 500kpa, in fact new housing developments have limiting valves just after the water meter to restrict the whole of home. This means that your dishwasher, fridge, washing machine, flexible undersink hoses etc are all protected from over pressure. The iStore is specified to have a pressure reduction valve in place to meet the design of criteria of 500kpa.
EXISTING INSTALLATION:-
Plumbing valves are susceptible to clogging if a significant volume of sediment passes thru the the pipework. Clogging of the valves may reduce the pressure delivery from the iStore but may also influence the operation also the anti-scald valve, it a significant amount of sediment blocks the protective screens at the valve the temperature of the water delivered to the house can be reduced.
There is nothing inside the iStore unit that can restrict the flow, it the pressure or delivery temperature is being effected then please call your installation plumber and discuss your concerns and possible service needs.