Liquid flow Piston filler

Hi,
I am trying to build a system to control liquid flow like ketchup using the method below in the link

http://www.fillers.com/piston%20filling%20machine%20guide.htm

Please can you guide me where can I get rotary valve and piston,did anyone else tried it, I could not find any schematics on Google.

Is there any other method much easier then this?

Could you just use a pressure system such the one used here:
http://www.betterthaneveryone.com/archive/2009/07/31/877.aspx

Or is the viscosity a bit too thick?

Eric

It will depend in part on what you are pumping since the materials used in the components must be compatible with the substance. For instance, for ketchup, all materials must withstand the acid level and water content. If you are pumping a substance that will be eaten/drunk eventually, your components will all need to be food-safe as well and will require proper regular cleaning.

Have you considered peristaltic pumps? Much easier to deal with if your liquid isn't too viscous.