The Karcher pump guard is a chemical that is designed to extend the life of the pump and the seals within. Pump guard or pump saver as it is also called, will lubricate the seals in the pump and also prevent any water that is left inside the pump from freezing during the colder months.
To use this product, you simply attach it to your garden hose water inlet fitting and turn the machine on for a few seconds. Once the chemical exits the outlet high pressure fitting, the pump is protected.
You should defintely run this chemical through the pump every time you are going to store your pressure washer away for extended periods of time such as over 30 days. You should also run this chemical through the pump periodically throughout the year to keep the seals moist.