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HVAC Pump Mechanical Seal Replacement: 9 Tips to Do It Right the First Time!

Mechanical seals in HVAC pumps prevent water from escaping the casing (wet end) around the shaft penetration. For a mechanical seal, dirt is the enemy. So, the cleaner your system’s water, the longer the seal will last. But, when the seal leaks, it MUST be replaced.

If you have not replaced your seal before, there are simple things that could sabotage what should be a relatively simple task. Below are nine tips from our experienced pump professionals that will help ensure your seal replacement is done right the first time:

  1. Carefully inspect the new seal and components for defects. If there ARE any defects, don’t try to work around them. Get another new seal.

  2. Clean the pump. Carefully clean the seal cavity in the pump, ensuring that the area is free from dirt, corrosion and pitting that might interfere with the stationary seat seal.

  3. Remove all old gasket material from casing and seal cap.

  4. Clean yourself. Be sure that you wash your hands after cleaning the pump and before opening up the new seal kit. And even though your hands are clean, don’t ever touch any mating parts of the mechanical seal with your bare hands. Pretend that you’re a surgeon and maintain a sterile seal.

  5. Use the lubricant provided in the seal kit, or a silicone-based lubricant, on the stationary seat o-ring and the rotating element. Do not use petroleum-based products for seal lubricant. Ever. And don’t allow any of the lubricant to get on the mating surface of the seal.

  6. Place a small amount of lubricant behind the rotating element to hold it in the cup during installation.

  7. To seat the stationary, use your hands with a clean rag or a paper towel or a piece of PVC pipe that is cut square and without burrs. Do not use any metal tools to install any component of the seat assembly. Check to make sure the stationary seat is sitting square in the casing.

  8. Rotate the pump shaft by hand for each step during the assembly process. Don’t relax spring tension on the rotating element once it has been loaded (compressed). If this happens, remove the rotating element and reset it in the relaxed position.

  9. When starting a pump for the first time, or at a seasonal changeover, turn the pump hand first before starting the motor. Remember, you should never run a pump “dry” (without water in it) even for a few seconds!

These steps may not completely guarantee success, but they should be considered before you install your next mechanical seal.

If you have questions or need assistance replacing your mechanical seals, you can contact your local manufacturer’s rep to schedule a visit by a field services technician. Additionally, you can review this video by Taco® Comfort Solutions™.

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