The Spray Pump System:

The Spray Pump System is used to protect the pistons of the single-acting pump from overheating. The cooling liquid is usually a mixture of oil and potable water and is circulated by a small pump. If the pistons were not cooled the sleeves would become hot and overheat within a few minutes. The cylinder surface must also be lubricated. The splash baffle on the extension rod prevents the cooling water from being carried to the pump crank-case by the extension rod.