Max. pressure
The highest pressure that the pump is capable of creating during operation. This parameter is directly related to the maximum head (see above); however, it is less obvious, and therefore, it is indicated rarely.
Minimum liquid level
The smallest depth of pumped liquid (from the bottom to the surface) at which the pump can operate normally. This parameter is indicated for submersible drainage models, for other types it is not relevant for various reasons.
Pump housing material
The material from which the pump housing is made. It is a structural element in which the working mechanism (impeller or auger) is installed. Note that the motor casing can be made of a different material — this is not important in this case; and in water pumps with the engine (see “Power source”), we are talking about the casing of the pump itself, and not about the support frame in which it is fixed.
The following options are most popular nowadays:
— Plastic. Inexpensive material that perfectly resists moisture and is not subject to corrosion. However, the reliability of plastic as a whole is not very high; the exception is special high-strength grades, but they are extremely rare in pumps (when strength is needed, metals are usually used). So plastic housing is mainly equipped with relatively simple and affordable models that are not designed for serious loads.
— Cast iron. An extremely popular material nowadays: cast iron is strong, reliable, durable and at the same time has a relatively low cost. However, in terms of corrosion resistance, this material is inferior to stainless steel (see below). Nevertheless, subject to the rules for operating the pump, the service life of the cast-iron housing is not inferior to the service life of most of the main components of the unit. Also note that such cases are quite massive, which makes transportation difficult; however, in some cases, a large weight is an advantage: it helps to dampen vibrati...ons.
— Stainless steel. By the name, one of the key advantages of stainless steel is high resistance to corrosion — and, accordingly, reliability and durability. On the other hand, this material also costs a little more than the same cast iron. The weight of such housing is somewhat less — this, again, can be both an advantage and a disadvantage, depending on the situation.
— Aluminium. Premium material. The aluminium alloys used in today's pumps are light, strong, durable, and virtually impervious to moisture, but cost accordingly.
— Brass. A fairly rare option found in some models of surface pumps. Brass is strong enough, reliable and resistant to moisture, but in most cases, it does not have key advantages over the same stainless steel or aluminium but costs a little more.
— Bronze. Another material similar to the brass described above is durable and practical but rarely used.
— Ceramics. A material found exclusively in sewage pumps in the form of toilet bowls (see "Pump design"). Most often, ceramics means vitreous china or more expensive and durable vitreous china — that is, the same materials as in ordinary toilets without built-in pumps.
