Pump Maintenance


Piston pumps have internal seals or packings that require changing periodically. A sign of these packings being worn is a small amount of paint appearing at the top of the pump where throat seal lubricant is placed.

If your pump is just starting to leak, this is a sign of pump wear and now is the time to service your pump. Changing the packings at the first sign of pump wear will prolong the life of the pump by lessening the wear of the hard parts.

Ignore or delaying packing wear can lead to pump component damage that is not repairable and a very expensive pump replacement may be required.

The general purpose of the packings is to create a seal, direct fluid flow and help the pump build pressure. There are two sets of packings – upper (or throat) and lower (or piston). Throat packings seal the displacement rod to the top of the pump cylinder. Piston packings create a seal inside the cylinder as the rod moves up and down.

These packings are designed to wear with use and will save wear on the hard parts. The packings are available in a repair kit and will include other recommended replacement parts such as the balls for the inlet and outlet valves and other gaskets, seals and o-rings.


While the pump is apart for service it is recommended to check the hard parts for wear or damage. Displacement rods (or pistons) and cylinders or cylinder sleeves should be replaced when worn beyond recommended limits and/or scoring is evident. They will usually last two sets of packings.

You should also check the seats of both the inlet (lower) valve and outlet (upper or piston) valve. The inlet seat can be turned over in some pumps giving double the life, the outlet or piston valve will need to be replaced when worn. As the piston valve is removed to replace the packings, now is the time to replace it if necessary.

A properly serviced pump will perform like new, but make sure everything is tensioned to factory settings and all instructions are followed to the letter.

Remember airless fluid pumps operate at very high pressure and can be dangerous if not properly maintained and operated.

It is advisable to have all repairs carried out in an authorised repairer’s workshop by factory trained technicians using genuine parts.