However, we know that the most effective Taco 006 pump does not have the ability to self-priming and very sensitive to the presence of gases in the fluid. The content of the air in the fluid in an amount of 5-7% can lead to failure of pumps and greatly reduces their efficiency. Applicable in some cases, self-priming recirculation Taco 006 pump have significant size and weight, lower efficiency than conventional Taco 006 pump.In addition, they have low self-priming ability and are unable to self-priming, even for small leaks in the suction line. The operation of these pumps the contaminated fluid leads to a rapid increase in the frontal gap between housing and open impeller, which further lowers their self-priming ability and efficiency.In the marine environment is often preferred as the Grundfos pumps piston or other types of positive displacement pumps. However, Taco 007 pumps have a lower than the centrifugal, the permissible height of the suction and pumping contaminated liquids require regular cleaning of the suction and discharge valves, as well as replacement Grundfos rings.Self-priming ability and opportunity to work on gas-liquid mixtures have many types of Taco 006 pumps. However, they are in most cases have low efficiency (30-35%), low flow and can not operate on liquids containing abrasive particles. Therefore, attempts to create a combined self-priming centrifugal plants with pumps and other devices with self-priming ability.