Using a Valve to control the Water Flow is not a good idea if you
want to reduce the flow over a longer period, the Pump is cooled
thru the water flowing it, if you reduce the amount of water getting out mechanically (i.e. Valve) then the Pressure switch on the pump will be
working overtime and eventually cut out (due to overheating) at sometime it might burn itself out.
Using a Valve to stop the water flowing is fine, if you want a permanent flow
control then a remote control would be the solution but is going to be expensive as it need to control something like the Vario from a distance.
I have seen a system utilising this method in Holland, If i can find there Internet site I will Post. Terry