Hy - Flo Pumps : Information

¤ Information ¤

¤ All pumps are 240V(UK) unless stated otherwise ¤

¤ General Information ¤

As Medcalf Bros ceased to trade several years ago, unless clearly stated otherwise, all Hy Flo pumps are, by default, second hand.

With regards to performance: All pumps have been serviced and thoroughly tested, and provide sufficient aeration for at least one decent-sized home aquarium, usually more.

With regards to condition: Unless clearly stated otherwise, all pumps are show-pieces, in good-to-excellent condition, well cleaned and correctly oiled. Pumps reaching a high price bracket are either rare (various colours and models exist) or particularly fine specimens, showing little-to-no-sign of use. We are quite happy to provide "youtube" movies of any pump running if you wish - please see here : here for an example.

¤ Identifying the Age of Hy Flo's ¤

To assist in determining the age of a pump, we have devised an arbitrary classification system, subdividing the pumps into four series (I to IV, where series I represents the first generation of pumps made by Medcalf, and series IV the last), as defined by the following characteristics:

Fly-wheel type.
Air-plate configuration.
Piston type.
Serial number.
Please note that while this system is in general accurate, it should not be taken as gospel.

Fly-wheel type:

Smooth finish - Series I and II.

Dimpled finish - Series III and IV.

Air-plate configuration:

Only two drilled holes - vacuum / airplate
Outlet and inlet both near bottom of plate
(corresponding to drilled holes)
Series I.

Four drilled holes
Outlets at top and bottom of plate.
Series II, III and IV.

Piston type:

Wide bore cylinder.
Removable from casing.
Series I.

Enclosed piston, narrow shaft.
Silvered piston casing, square edges.
Series II.

Enclosed piston, narrow shaft.
Silvered piston casing, rounded edges.
Series III.

Enclosed piston, narrow shaft.
Black "lacquer" finish piston casing.
Rounded edges.
Series IV.

Serial numbers:

Very Early pump, series I.
Black plate with Holtwhite Avenue Address
Serial number on left, numerals only

Early, Series I and II.
Serial number on left, numerals only
Riveted flat plate.

Early, Series I, II and III.
Alphanumeric serial number on right
Riveted flat plate

Late, Series I, III and IV.
Alphanumeric serial number on right.
Sunken plate with printed rivets.

Late, Series I, III and IV.
Alphanumeric serial number on right.
Sunken plate with no rivets.

For a full list of all recorded pump plate with serial numbers, please click here.

List pumps by their respective series:

Series I - Series II
Series III - Series IV