Originally Posted by VocalNeal
Originally Posted by expat2010
It seemed to me that on the tiny schematic inside the pump that the spring is not to do with multi-story, but the level of the water supply. There's a diagram showing a lower water supply. Maybe to stop the water suctioning out?
Actually it is to maintain the prime and stops the water from draining back into a well and allows the pump maintain the pressure in the accumulator. In a multistory house the water in the upper floors would drain back to the pump. A broken spring will result in water hammer in the system.
In a urban single storey house system connected to government water the anti-drain back function may not be necessary but doesn't do any harm.
This style of pump isn't for a well at all. That would be a jet pump your referring to. No prime issues with this style pump but the check valve spring should be left in there regardless. Dunno why somchai thought it was a good idea to remove it.