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Pumps & Motors (cont.)


Replacing the Mechanical Shaft Seal

 

All pumps have seals to prevent water from leaking out along the motor shaft. When these wear out due to overheating, vibration or a sudden change in water pressure - you will need to replace your pump shaft seal. The first thing to do is to turn off the electricity to the motor at the circuit breaker.

  1. To access this seal for replacement, remove the four bolts that hold the pump halves together, it is not necessary to remove the entire pump from the plumbing system.

  2. Grasp the motor and pull it and the bracket away from the pump volute. Wiggle it slightly from side to side as you pull back to help break this joint.

  1. Take your pliers or a wrench and hold the shaft extender to prevent it from turning. Unscrew the impeller from the shaft extender using an impeller wrench. You can also wrap a rag over the face of the impeller so you don't cut yourself and twist it off by hand. As a last resort, hold a large screwdriver against the impeller and tap it gently with a hammer. Use care not to damage the impeller. Use even more care that the screwdriver doesn't slip and damage you.

  2. Remove the four bolts that hold the bracket on the motor. If needed, use a hammer to gently tap the bracket away from the motor.

  3. Remove both halves of the old seal. Notice how each half is installed so you get the new one back in the same way. One half is in the back of the impeller and is easily popped out with a flat-blade screwdriver. The other half is in the seal plate and motor bracket unit. Lay the bracket on your workbench with the seal on the bottom. You will see the back of the seal through the hole in the seal plate. Using the flat-blade screwdriver once again, put the tip on the back of the seal and tap it with a hammer. It will pop out easily.

  4. Install the new seal. First, look up your pump in the manufacturer's literature or supply house (Poolcenter.com!) catalog to determine what model seal you need.  Clean out the seal plate and impeller where you have just removed the old seal. Use an emery cloth or a small wire brush and water. Dry each area and apply a small amount of silicone lubricant to help the new seal slide into place. Install each half of the seal the same way you removed the old one, white ceramic of one half facing the glazed carbon ridge of the other half. Use care in installing not to damage, nick or soil the face of either seal half.

  5. Gaskets. When you break apart a pump, the old gasket usually won't reseal. Clean all of the old gasket off of the seal plate and volute. Scrape it clean if needed with a flat blade screwdriver. Now reassemble the pump the same way you took it apart, placing a new gasket between the pump halves.

  6. Check for leaks by starting the pump and let it run several minutes. A fresh paper gasket might leak for a few minutes until it becomes wet and swells to fill all the gaps, but it should stop leaking after a short time. If your job does leak, take it apart and go over each step again, making sure the seal halves are seated all the way and that there is no corrosion or debris left in the impeller or seal plate that might prevent the new seal from seating completely. You may add some Blue RTV silicone sealant to help a paper gasket.

In some pumps where the parts are assembled differently, you follow the same steps. The clamp is removed to disassemble the pump halves, and you must remove the diffuser to get to the impeller. To remove the impeller you can grip it with your hand and twist it off, but the trick with these units is to stop the shaft from spinning as you twist off the impeller. There are air vents in the motor on the end closest to the pump itself. Look in and you will see the motor shaft. Place a flat-blade screwdriver in one of the air vents and wedge it against the shaft to keep it from turning.

 

Alternatively, you can remove the end cap and look inside as you twist the impeller. You will see the back end of the shaft, with the start switch attached. Since this switch is fragile, you must remove it (one screw) to access the slotted screw in the back end of the shaft. Place the screwdriver in this screw to keep the shaft from turning as you remove the impeller. Or use a 7/16" wrench on the back of the shaft.

 

Instead of a gasket, some pumps use an O-ring. Clean this and lubricate it before reassemble. If it has stretched and it seems like there is too much O-ring for the channel in the volute, try soaking the gasket in ice water for a few minutes to make it shrink a bit.

 

Some pumps use a plastic impeller with a housing that holds half the seal in place. If the pump has run dry and overheated the pot, this housing might be warped and the seal will not fit tightly. The only solution is to replace the impeller. This is a common problem with automatic cleaner pumps, which are not self-priming.

 

Remember to use only non-hardening silicone lube like Magic Lube on all pool and spa work. Make Sure not to use Vaseline or other lubricants that are made of petroleum, which eat away some plastics and papers.

 

Clogged Impeller?

 

When your pressure is high, your filter is dirty, right? When your pressure is lower than normal, your pump basket is dirty. If the basket is clean, yet pressure and flow is still low or surging, you may have an air problem or the impeller may be clogged. Something prior to the filter is obstructed. To unclog an impeller follow these steps:

  1. Shut off power, remove motor and seal plate from pump. Sometimes this is one clamp that holds the motor to the pump, or some pumps have nuts or bolts to remove.

  2. Stand motor on it's end, remove any diffuser or impeller shroud, and using needle nose pliers or a thin screwdriver, remove the clog. Run some heavy wire through the vanes of the impeller.

  3. Reassemble pump snugly and tightly. Fill pump pot with water. Restart pump. Pressure then should rise.

 

Locating an Air Leak...

 

Make sure the strainer lid is on tight, with a clean, lubed o-ring. Also check that all plugs are tight. A good trick in locating an air leak is to shut off the motor when it's under full pumping head pressure, and look for water to spray back out of the void where the air was entering. You have to be quick to catch this spray-back! This void will always be before the impeller. After the impeller is what we call "the pressure side."  Any leak or void here will leak water out. Any leak or void prior to the impeller (in front of the pump impeller) will draw air in when the pump is on. The pump will "pump" air if it can, it is the path of least resistance. So, your system needs to be almost airtight to run properly. When you find this void, patch with epoxy putty or silicone, or replace the part if needed.

 

If that didn't work, you can do this...buy a Drain King at your local hardware store (or we can send one for $20.95 + S & H). This connects to a garden hose and puts the line under pressure. Putting this in the skimmer, you can turn on the hose and pressurize the line backwards (Also Great for clearing clogged pipes). Remove the pump lid and use a plug at the pump entrance. This will allow pressure to build up in the line and squirt out at the leak. Many suction side leaks found in this manner are then repaired with pool putty, or a more permanent plumbing repair / pipe replacement can be made. (continued........)

 
 

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