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Simple Pump Maintenance - 125CA Cylinder Piston Seal

May 22, 2024
5 min read

Pump Cylinder Piston Seal Maintenance on the Simple Pump 125CA Pump Cylinder

Changing The Piston Seals on the 125CA Pump Cylinder

In order to replace the u-cup seals on the pump cylinder piston, the pump system must be pulled from the well as the piston is in the pump cylinder at the bottom of the pump system.

Remove the Piston from the Cylinder

  1. To remove the piston from the 125CA pump cylinder, use use a vice or two sets of pipe wrenches to secure the cylinder.
  2. The piston always has to go in the top and out of the bottom of the pump cylinder. That's because the U-cup seals are directional and they can't get past the threads if we go the wrong direction.
  3. To remove the bottom seat, unthread the seat with a pipe wrench. Note: be careful because there is a ball in the cylinder that is going to come out. Put the ball and the bottom seat to the side after removing them from the cylinder.
  4. Remove the adapter from the top of the pump cylinder using a pipe wrench. In the newer cylinder style, the adapter has the same threads as the bottom seat. The adapter includes an O-ring that needs to stay in the adapter. The older style adapter is an MPT thread that is a bushing that has been turned down. It will be a little different, but still installs the same way.
  5. Put the adapter to the side.
  6. Once the bottom seat and adapter have been removed, push the piston through the bottom of the pump cylinder.

Change the piston seals.

All 125CA pump cylinder models prior to 2023 use two types of o-ring seals. They use two buna o-rings and two urethane o-rings. The urethane o-rings are on the outside top and bottom of the piston. The buna o-rings are the two middle seals on the piston.

Starting in 2023, we utilize four of the same style of seal and it's EP rubber, for durability, seal life, and easier maintenance.

Removing the Seals

  1. Using a sharp point tool or small flat tip screwdriver, get underneath the seal to pull the seal off of the piston.
  2. Don't worry If the seal is damaged getting it off the piston.
  3. Make sure the seal groove is clean and clear of debris before replacing the seals.

Replacing the Seals

  1. Once the old seals are off, start with the seal on the inside of the piston. If you have an older seal kit, this will be one of the buna o-rings. The seal u-cup needs to be pointed up towards the piston rod because it's going to spread when you're lifting the water and push it against the side of the cylinder.
  2. Get the o-ring just over the edge of the piston into the seal groove. The first couple of times you do this may be a little tricky. Get your tool underneath the o-ring and bring it around the piston to the middle groove.
  3. Continue replacing the remaining seals on the piston

Re-installing the Piston

  1. Re-install the bottom seat of the cylinder. Make sure the o-ring is in place and clean from debris. The bottom seat is very different than the adapter as the bottom seat has 1-inch NPT threads and a hole on the bottom.
  2. Using a pipe wrench, screw on the bottom seat tight to the cylinder.
  3. Reinsert the ball into the cylinder so that it is below the piston.
  4. Insert the piston past the threads on the top of the cylinder. Putting the cylinder vertical and wiggling the pump rod as you're pushing piston through the threads may help make this process easier.
  5. Prior to reinstalling the adapter to the top of the cylinder, remove the adapter o-ring and make sure it is free of debris by pulling it through your fingers to get it to loosen up. Put it back on the adapter prior to re-installing the adapter.
  6. Thread the adapter back onto the cylinder. Use a pipe wrench to get the adapter tight to the cylinder and seat the o-ring.Now the 125CA pump cylinder is ready to be reinstalled to your well.