Define "not working properly".

Not pumping, not enough fliw, not enough pressure, motor keeps tripping, ???

These look like central heating pumps?

What is data? (Fliw, head etc)
What flow or pressure do you need?

These pumps won't"lift" very well and usually work under pressure in a closed circuit.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

When three different new technical items all are not working like intended, you are probably not using them according to the correct technical limitations.

For pumps check: fluid conditions (degree/type of particles in fluid, sugar, alcohol), temperature, alcohol,compatibility of sealing and other materials to fluid, correct start (wet or dry), sucking height and pumping height, cleaning after use, lubrication and maintenance.

Sugar or residues on components?

If you have brought and tried 3 pumps, there is a fair chance that it's the application / the way you are using them that's the problem.
Would help to write up a technical description of how, what, where, why - - give us something to look at.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

Giannis13,

Please describe your system. I see that you have an "automatic brewing pot" there, so I'm kinda confused on why you would need an extra pump. Are you using this pump to move the sparging water?

I use an HERMS system with a regular sanitary pump and have to yet encounter a problem with the system (apart from my brewing friends destroying the pump's seal one time by restricting the inlet - someone call the pump police please).

So, again, describe exactly what you are trying to accomplish with your pump and then we can think of a solution.