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What is the thread size in the impeller of a dynajet 50 pressure pump please

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The thread size of this impeller is the same for all threaded shaft impellers. they are universal in size of the threads on the shaft of the motor.

U S Parts Center

Posted on Feb 04, 2013


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How to replace plastic impeller with brass(metal) impeller

I called Lowes then Utilitech and they sent me a new impeller. There were no instructions about how far to thread the impeller onto the post. I am going back in to thread it all the way to the top. I wish I had requested a brass impeller.

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Waterway model # pf-50-2n22c

The wet end of pumps come off this way.

  • Remove the face plate of the pump.
  • Put a large flat-head screw driver on the back of the motor on the shaft going thru the motor.
  • Grasp the impeller (with the screw driver in place on the back of the motor) and unthread the impeller counter clockwise.
  • If it doesn't unthread you will need to bust it off
  • On the back of the motor you will find 4 small bolts 1/4" size that run all the way through the motor and thread into the four fingers of the wet end.
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Mar 14, 2013 | Waterway Pool & Spa

1 Answer

Our centurion pool pump motor Model B128 replaced less than 1 year ago. Pool company has to replace the impeller twice. Is this common? I believe the pool co sold and installed a used pump instead

Broken impellers generally are not caused by the pump's motor. Impellers usually fail due to back pressure from the filter when the pump shuts off. Air in the filter is compressed while the motor runs, on your pump 12-15 psi. or a bit higher.

When the motor shuts off that compressed air forces water back to the pump, sometimes with enough force to loosen (or completely throw off) the impeller. If the impeller is loose when the pump starts up again it will instantly re-thread the impeller and strip out the threads.

Check to see if you have a suction leak. After the pump has turned on, bleed the air out from the air relief valve on top of the filter. After the pump has run for a while open the air relief valve and see if air comes out. There should be no air, or just a little.

I have seen this back pressure strong enough to blow the skimmer basket up onto the deck.

What make and model of pump and filter do you have?

Feb 22, 2013 | Pool & Spa

1 Answer

Thread size davy dynajet 50 impeller

These thread sizes are all the same for a threaded shaft motor. The impellers are universal as far as that goes.
The question you should ask is about the hp of the impeller and match that to the model of pump you have.

US Parts Center

Jan 17, 2013 | Pool & Spa

1 Answer

Impeller spins when i'm holding the shaft. what would cause this problem or is it? i have no pressure.

Late answer but might help someone else out.
There is a nut molded into the impeller. If the threads are stripped or damaged the motor shaft will spin and not move the impeller. You'll have to take the pump apart to diagnose.

Apr 30, 2012 | Polaris Pb4 - 60 Booster Pump

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I have a whisperflo. I've ran the motor without water and it's quiet. Add water and it makes a pretty good racket (not a bearing whine). I've even tested without my filters to eliminate head pressure) ...

Yes the impeller is screwed on right handed normal thread. *** Info below pasted form one of my other posts *** You need to lock the motor and unscrew impeller. Depending on the motor, you remove a cap in the middle of the tail piece and hold with a wrench, (usually 9/16") or remove a cap that covers the whole end and grab the shaft with a wrench (usually 7/16") by sliding it under one of the components (not sure exact part off top of my head have to look at it) and then turning impeller. If the impeller has a bolt or screw in the middle remove that first. (you already did this.) It should be reverse thread so make sure you don't turn the wrong way and break or strip. If there is no screw, or after you've removed it, just spin the impeller off (it should be counter clockwise standard thread). If you can't do it by hand and assuming you don't have an impeller wrench, be very careful and use a large pliers, pipe wrench, or strap wrench to loosen it.

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How do you remove the impeller and mechanical seal off the pump shaft? I am wanting to change the main bearing that sits inside the motor housing of a Onga pool pump PPP750 model.

The impeller is screwed on to the shaft, you need to pull the cover off the end of the motor opposite the pump so you can hold the shaft to keep it from turning. The impeller should unscrew with just hand pressure, most are a standare SAE thread and turn counterclockwise to remove. Hope this helps.

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Most of these style knock off in a counterclockwise direction. The impeller is usually threaded onto the shaft that way. A small brass drift and hammer should move it easily.

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Execetive 56 4hp pump

Looking at the face of the pump, the impeller unscrews by turning it counterclockwise. Also, for some strange reason, the 4HP pump gets a 3HP impeller; the rating is embossed, in very small letters, near the center of the impeller. The 3HP impeller part number is: 310-4200.
Be sure to change the seal: US Seal P/n: PS-1000.

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