Maric flow control valves are Australian Made, extremely reliable, have no moving parts, don't require adjustment, do not require electricity and, perform an extremely difficult function with ease.   The Maric flow control valve does exactly that, it controls the rate of flow through the valve to a specific maximum volume per minute.   When a bore pump starts, upthrust can be an issue however with a Maric valve installed correctly, upthrust issues are eliminated.   Likewise, when some bore pumps startup the static head is only a few meters and if left unrestricted, the flow would far exceed the safe volume and cavitation would occur.   The Maric flow control valve eliminates cavitation in bore pumps caused by excessive flow.   For further technical information, click on the link.  http://maric.com.au/wp-content/uploads/Maric-Application-PUMP-PROTECTION.pdf