pulsing filter pump: how to diagnose?

[agonista]

Hello TFP!

I am getting close to the end of a successful SLAM, have had the filter pump running 24/7 since the afternoon of Saturday June 24th, and the filter pump has been making a loud pulsing sound with a rough periodicity of 1 second for the past 3 days. The pump has 5 days of continuous operation apart from episodic filter cleanings that take 30-45 minutes per day. This sound persists even immediately after I clean the cartridge filters and restart the pump.

The pool is 26k gallons, PVC runs are 2", and the pump is a Waterway SMF-120 (single speed). There are no suction side leaks, evidenced by the completely full pump basket. The pump motor is running hot enough that I cannot safely touch it for very long, which is partly related to it being unusually hot here in Tampa the past several days (90-95 F).

I am interested in input on how to diagnose what is going on with the pump and/or its motor. I am adept with low and high voltage electrical and can check the motor housing temperature using infrared.

Thanks for reading!

 

[Jimrahbe]

A,

Most "pulsing" pumps are caused by a weir door that is sticking up. This causes all the water in the skimmer to get sucked out. This in turn causes the weir door to slam open, letting the water back into the skimmer basket.. Rinse and repeat..

Thanks,

Jim R.

 

[agonista]

A,

Most "pulsing" pumps are caused by a weir door that is sticking up. This causes all the water in the skimmer to get sucked out. This in turn causes the weir door to slam open, letting the water back into the skimmer basket.. Rinse and repeat..

Thanks,

Jim R.

I just went out and had a look at the 3 weir doors and they all are moving freely, nothing is stuck AFAICT.

The pulsing frequency is more like 2 Hz.

 

[duraleigh]

If the weirs checked out, you probably have a suction side leak. Air is getting into the suction line between the skimmer intake and the pump. Hard to find sometimes but most always easy to fix.

Your pool water level is high enough so you are not sucking air into the skimmer.........yes?

 

[Jimrahbe]

A,

What size filter do you have, and what is the current filter pressure.

Can you feel this pulsing at the returns?

Have you used Floc, or Clarifier, or Phosphate remover with your current cartridges?

Not sure you want to run any tests, but if you do, I'd remove the cartridges and see if the pulsing goes away,

Thanks,

Jim R.

 

[agonista]

If the weirs checked out, you probably have a suction side leak. Air is getting into the suction line between the skimmer intake and the pump. Hard to find sometimes but most always easy to fix.

Your pool water level is high enough so you are not sucking air into the skimmer.........yes?

All 3 skimmers have water flowing into them, no air.

Per my original post "There are no suction side leaks, evidenced by the completely full pump basket.". The pump basket window shows only water, no bubbles.

 

[agonista]

A,

What size filter do you have, and what is the current filter pressure.

Can you feel this pulsing at the returns?

Have you used Floc, or Clarifier, or Phosphate remover with your current cartridges?

Not sure you want to run any tests, but if you do, I'd remove the cartridges and see if the pulsing goes away,

Thanks,

Jim R.

The flow at the returns is steady, no pulsing that I can detect.

My maintenance service did indeed use floc, phosphate remover, and a metal remover, but I am unsure which of these, if any, went through the filter. Taking over from this service has been a mess. I have another post in this same subforum - which I don't think I can link to - about issues with my filter from today, it should be quick to find. The filters have a clean pressure of 16-18 PSI, which feels high. I may end up having to replace the cartridges because they were left out in the Florida sun for a week, likely damaging them.

I will remove the cartridges tomorrow morning when I clean the filter to see if that changes anything.

 

[mknauss]

If floc is run through cartridge filters, they are typically ruined. You can try soaking in TSP, but not guaranteed.

 

[duraleigh]

The flow at the returns is steady, no pulsing that I can detect.

If the pump is pulsing, that's because the flow of water through the pump and into the filter is pulsing as well. You should see this easily on you psi gauge.

 

[agonista]

If the pump is pulsing, that's because the flow of water through the pump and into the filter is pulsing as well. You should see this easily on you psi gauge.

The gauge reading is steady, so despite there being audible pulsing from the motor, that does not translate into gauge reading pulsing.

I removed the filters, closed the filter housing, restarted the pump, and the pulsing sound is still present with the filters removed.

Maybe the motor is going bad.

 

[1poolman1]

The gauge reading is steady, so despite there being audible pulsing from the motor, that does not translate into gauge reading pulsing.

I removed the filters, closed the filter housing, restarted the pump, and the pulsing sound is still present with the filters removed.

Maybe the motor is going bad.

Audible "pulsing" with no change in the pressure on the filter or variance in water flow from the returns is usually the sound of an issue with the bearing cup at the rear end bell of that motor.

Those pumps came with a Century 56-frame motor. For some reason the rear cup where the bearing sits was either slightly large or the material was too soft or affected by the heat of the motor running, never got a definitive answer from Century. If the impeller got slightly out of balance (debris usually) the entire shaft could move with the most motion at the rear of the motor. Never saw it on the 48-frame motors.

That resulted in what I always referred to as the "rum-rums." The quick fix was to remove the through bolts that hold the motor together (if possible, they can break on an older motor), remove the end bell from the shaft (it will tap off easily once that sound starts), and wrap about 5 wraps of Teflon tape around the bearing. Put it back together and the noise will be gone, sometimes for the rest of the life of the motor, sometimes for just a short while as the end bell is damaged. Did so many it got so I could do it in about 15 minutes.

 

[Jimrahbe]

@1poolman1

Just so I understand.. There is no real surging of any water, it is just a sound from the pump.

What if you did nothing, what would happen???

Thanks,

Jim R.

 

[1poolman1]

@1poolman1

Just so I understand.. There is no real surging of any water, it is just a sound from the pump.

What if you did nothing, what would happen???

Thanks,

Jim R.

Eventually the motor shaft will move so much the rotor will start to hit the stator, then its new motor time. They get very loud when that starts to happen. Or, the shaft will just be magnetically frozen to the stator. You can hear it happen when the pump is energized. Then the breaker trips if it hasn't already been doing that. Instant overload.

 

[agonista]

Audible "pulsing" with no change in the pressure on the filter or variance in water flow from the returns is usually the sound of an issue with the bearing cup at the rear end bell of that motor.

Those pumps came with a Century 56-frame motor. For some reason the rear cup where the bearing sits was either slightly large or the material was too soft or affected by the heat of the motor running, never got a definitive answer from Century. If the impeller got slightly out of balance (debris usually) the entire shaft could move with the most motion at the rear of the motor. Never saw it on the 48-frame motors.

That resulted in what I always referred to as the "rum-rums." The quick fix was to remove the through bolts that hold the motor together (if possible, they can break on an older motor), remove the end bell from the shaft (it will tap off easily once that sound starts), and wrap about 5 wraps of Teflon tape around the bearing. Put it back together and the noise will be gone, sometimes for the rest of the life of the motor, sometimes for just a short while as the end bell is damaged. Did so many it got so I could do it in about 15 minutes.

Just to confirm, you're referring to the rear bearing, not the front, right?

I've had a look at a couple videos about replacing pump motor bearings to see what the process is like for motor disassembly. Am I right to assume I will need no special tools for this?

Are there any other potential issues or repairs that I should plan for while doing this, e.g. replace the shaft seal or check bearings?

Since it's a holiday weekend and I'm not keen to risk breaking through bolts or causing other issues that lead to pool problems, how urgent is fixing this? I should be able to get this done later this coming week and may want to order some other replacement parts in the meantime.

I appreciate your sharing your mechanical domain knowledge.

 

[1poolman1]

Just to confirm, you're referring to the rear bearing, not the front, right?

I've had a look at a couple videos about replacing pump motor bearings to see what the process is like for motor disassembly. Am I right to assume I will need no special tools for this?

Are there any other potential issues or repairs that I should plan for while doing this, e.g. replace the shaft seal or check bearings?

Since it's a holiday weekend and I'm not keen to risk breaking through bolts or causing other issues that lead to pool problems, how urgent is fixing this? I should be able to get this done later this coming week and may want to order some other replacement parts in the meantime.

I appreciate your sharing your mechanical domain knowledge.

To pull bearings you need a bearing puller of some type, they are a press-fit item, and a way of reinstalling them. I always replace any seal that has been disturbed by a repair.

Rear bearing, yes. But, it is not a problem with the bearing but with the end-bell of the motor, the shaft is actually moving side-to-side or up- and-down. Rear bearings seldom cause an issue on a pool motor. Yours could be bad as well, but then the noise would be continuous, not pulsing.

You should seriously consider replacing the motor with a variable-speed one. That sound can last for years or weeks. It will get worse, but no one can say when.

 

[agonista]

To pull bearings you need a bearing puller of some type, they are a press-fit item, and a way of reinstalling them. I always replace any seal that has been disturbed by a repair.

Rear bearing, yes. But, it is not a problem with the bearing but with the end-bell of the motor, the shaft is actually moving side-to-side or up- and-down. Rear bearings seldom cause an issue on a pool motor. Yours could be bad as well, but then the noise would be continuous, not pulsing.

You should seriously consider replacing the motor with a variable-speed one. That sound can last for years or weeks. It will get worse, but no one can say when.

I have an old Jandy Aqualinks RS control system that was installed roughly 2008. Would I need to also update the control system to take advantage of a variable speed pump?

 

[1poolman1]

I have an old Jandy Aqualinks RS control system that was installed roughly 2008. Would I need to also update the control system to take advantage of a variable speed pump?

Century ECM16SQU would work with the relay in the Jandy. Though not made anymore, they are still available online, give more control, and are a very good motor.

The Century EVQ165 is the same motor with a different control, less options for the user, but will also work with the Jandy through the existing relay.

 

[agonista]

That resulted in what I always referred to as the "rum-rums." The quick fix was to remove the through bolts that hold the motor together (if possible, they can break on an older motor), remove the end bell from the shaft (it will tap off easily once that sound starts), and wrap about 5 wraps of Teflon tape around the bearing. Put it back together and the noise will be gone, sometimes for the rest of the life of the motor, sometimes for just a short while as the end bell is damaged. Did so many it got so I could do it in about 15 minutes.

I've disconnected and disassembled the motor, but as you mentioned, the through bolts are seized. I've given them several rounds of penetrating oil and a couple rounds of hand torch heat with no effect. I can feel the torsion in the bolts and get zero movement in the threads at the front of the motor when twisting gently with a socket wrench. This pump motor is from 2018 (going off serial and capacitor date), so I'm surprised the bolts are this bad.

Does it make sense to replace just the motor versus the entire pump? It would be nice because it would not require replumbing the PVC.

Depending on the lead time to receive a replacement motor or pump, I may just reassemble the existing pump until I have time to install the replacement.

 

[1poolman1]

I've disconnected and disassembled the motor, but as you mentioned, the through bolts are seized. I've given them several rounds of penetrating oil and a couple rounds of hand torch heat with no effect. I can feel the torsion in the bolts and get zero movement in the threads at the front of the motor when twisting gently with a socket wrench. This pump motor is from 2018 (going off serial and capacitor date), so I'm surprised the bolts are this bad.

Does it make sense to replace just the motor versus the entire pump? It would be nice because it would not require replumbing the PVC.

Depending on the lead time to receive a replacement motor or pump, I may just reassemble the existing pump until I have time to install the replacement.

Seized through-bolts usually are caused by a shaft seal leak. Its really new motor time if you don't want to replumb. As sent before:

Century ECM16SQU would work with the relay in the Jandy. Though not made anymore, they are still available online, give more control, and are a very good motor.

The Century EVQ165 is the same motor with a different control, less options for the user, but will also work with the Jandy through the existing relay.

You would also need a shaft seal and O rings. This is the best price for that pump's kit that I've seen:

Amazon.com

 

[agonista]

Seized through-bolts usually are caused by a shaft seal leak. Its really new motor time if you don't want to replumb. As sent before:

Century ECM16SQU would work with the relay in the Jandy. Though not made anymore, they are still available online, give more control, and are a very good motor.

The Century EVQ165 is the same motor with a different control, less options for the user, but will also work with the Jandy through the existing relay.

You would also need a shaft seal and O rings. This is the best price for that pump's kit that I've seen:

Amazon.com

Derp, I should have read your earlier post more closely.

I will replace the motor. Appreciate the link to the rebuild kit because I had seen a few places that didn't seem to have the shaft seal part.