Doctor Drivel wrote:
wrote in message
...
daestrom wrote:

Unless there is a permanent vent at the top, it won't 'drainBACK'.

Au contraire. It will, with a collector above an unpressurized tank with
the ends of the supply and return pipes underwater and a small hole above
the water line. This would need less pumping energy than a system with
the return pipe above the water line. Neither needs a vent at the top,
if plumbed with all pipes downhill.

You have to maintain the water level in the tank, otherwise no drain down.
The air hole in the pipe needs to be exposed when the pump is operating. If
the water level is too high then no drain down. Some sort of level
maintaining mechanism needs to be installed, such as a ballcock valve and
float. Then if this fails an overflow is needed. This is self regulating,
but you can do it by making a level line and using a hose pipe I suppose.

simpler to have the vent hole above the top of the tank. Add a sleeve
to prevent splash possibility.


NT