Weird noise/cavitation intermittently w/ pump. No problems suction or pressure side. I'm stumped.

Skypalace

Active member
Jun 25, 2020
31
Seattle area
Hi folks! New member here. I hope it's ok for my first post to be a request rather than helping someone else out, but now that I'm here I'm happy to help. I'm not in the industry, I'm a homeowner that happens to be an engineer, so I maintain and repair all my own systems.

I have a very strange problem. My pump (1HP Pentair WhisperFlo, new in 2012) for my 20k gallon inground pool has started having two modes of operation - one is quiet and normal, tons of flow, great pressure. The other is that it's very noisy, I'll get some cavitation in the basket, with almost no flow. So I can't leave the system to operate on schedule, as if it starts in 'goofy' mode I'll get no flow and a pump that sounds very bad.

Turning the pump on and off at control panel (Pentair EasyTouch) is like spinning a roulette wheel, it'll come back on in 'normal' mode, or 'goofy' mode, and I can tell by the sound within about 3 seconds. That mode will last until the pump is restarted, ie. if it's in normal mode, will stay that way for hours. Same in goofy mode, it never calms down and starts flowing. So it can't be a systemic problem with blocking on either suction or pressure side. No air in system when operating properly so no air leaks on suction side. Turning pump on and off at control panel will randomly turn pump on either normal or goofy, nothing else has touched or changed, and the two can alternate just seconds apart, no time for things to cool down or system to lose prime, etc.

I took the pump apart, the diffuser and impeller are totally clean, no cracks, no leaking in the case at all. I didn't pull the impeller off the motor shaft (didn't want to mess up the ceramic seal), but motor w/ impeller spins totally free and quiet, no shaft bearing noise at all. Relubed all the gaskets, ensured seated, cleaned all the mating surfaces, put it back together, and worked great! Until I shut it off and on a couple of times, then back to 'goofy mode', so problem (in its intermittent glory) is back.

I see no problems suction side - exact same behavior in 4 different suction modes (spa/pool Jandy valve just before motor, and pool side has two manual ball valves for skimmer and pool bottom return). Either of 4 modes (all spa, all skimmer, all pool bottom, or 50/50 skimmer/bottom (both ball valves open), still happens, and I'll get 100% flow in all those modes also when pump is in 'normal' mode. Same on pressure side - Jandy valve to pool or spa return. When in 'normal mode' tons of flow (probably 80gpm) and pressure (about 19-20psi on my Pentair 410 cartridge filter). Everything is 2" pipe.

I'm 99.9% sure it's not plumbing related, but something in the motor itself. I have 4 possible theories, not sure how to test/validate easily beyond what I've done:
1) Occasional binding on output shaft, so it's sometimes spinning freely, sometimes binding at bearing. Weird though that it's 100% fine or not, never changes while the pump is running though.
2) The motor itself is acting up.
3) One wacky thought I had is that perhaps the control board is sometimes only switching one pole of the 240v so motor (in 240v mode) is only getting 120v sometimes.
4) There is something at the impeller that I haven't been able to see with visual inspection, perhaps a missing internal piece that sometimes is causing a resonance/vibration, and other times not, or perhaps something with the ceramic or shaft seal.
5) Something else that I've missed.

Here's a shared video link, video is a little over a minute, first two times the pump is turned on it's in 'goofy mode', I move the phone around to try to locate the noise (wet vs motor side) but can't locate it. When I let the pump sit for about 10 seconds, and restart it at the :55 second mark, it immediately starts in 'normal mode', you can immediately hear the sound difference, and the pump fires right up and flows water great, 20psi on pressure side, jets in the pool are as strong as they've ever been.

 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
19,402
Northern NJ
Let’s add @mas985 to the discussion.

My observation is you have a big air bubble in the pump basket and low filter pressure in crazy mode. Like the pump is not priming correctly. That is usually indicative of a suction side air leak.

Have you checked the O ring on the pump lid and used Pool Lube in it?
 

Skypalace

Active member
Jun 25, 2020
31
Seattle area
Let’s add @mas985 to the discussion.

My observation is you have a big air bubble in the pump basket and low filter pressure in crazy mode. Like the pump is not priming correctly. That is usually indicative of a suction side air leak.

Have you checked the O ring on the pump lid and used Pool Lube in it?
Yes and yes, as well as double checking the O ring at the union just before the pump. That was an initial theory I had.

When pump in 'normal' (quiet) mode, not a single air bubble getting into the system. The air in the video is there because I'd stopped the system, and after a while I get some air from the top of the cartridge filter pushing back into the pump. On 'normal' operation (ie. 50% of the time I turn the pump on) it pushes that bubble out of the system in a few seconds (as you can see at the ~1:00 minute mark in the video).

As I mentioned, if I stop and start pump, without touching anything else, it'll start working great, zero suction side air, from any of the 3 possible suction sources. Once pump is in 'normal' mode I can switch the suction side to any of the 3 inputs (spa, skimmer, pool bottom), all have full flow (20psi at filter) w/ zero air bubbles.

So again, the fact that the pump, half the time, operates perfectly, and once in that mode, will so operate until the end of time (or until the pump shuts off, whichever comes first) makes me doubt that I have any kind of systemic plumbing issue, on either the suction or the pressure side. Otherwise, it would always act that way (until I fixed the plumbing issue).

When the pump is in 'goofy' mode, it basically cavitates and doesn't pump, so air in the basket will stay there. Note that I've also been able to repro this with zero air in the basket (system operating 'normal' mode, turn pump off and on, it's in 'goofy' mode, I'll see whatever bits of debris (pieces of leaves etc) swirling around in the basket, not getting sucked to sides/bottom of the basket as when proper flow. So the 'goofy mode' does not always have large amounts of air in the basket. I could post more videos (I took a bunch of them) that all show the similar behavior, but I figured I'd just post one short one that shows both normal and 'goofy' behavior.

Also, suction side leak doesn't explain the strange noise of the pump. I've sucked air before (accidentally drained spa too much and cleared line, or had low water level at skimmer) and it's not making that funny/loud noise.
 

Skypalace

Active member
Jun 25, 2020
31
Seattle area
I think you have to remove the motor and examine the impeller.

Let’s see what other folks say.
Did that, sorry for the long post, lots of details I had hidden in there :)

Diffuser and impeller look fine, no debris, cracks etc. Diffisuer O-ring has never lost a drop of water, inside of housing looked brand new, not a drop of water in there. I didn't remove the impeller from the shaft (didn't want to mess up the ceramic bearing, I don't have a spare on-hand) so didn't look at the inside/back of it, but looked fine and clean from a visual inpection.

Motor (w impeller attached) running fine and quiet, no bearing noise.
 

zea3

Mod Squad
TFP Expert
LifeTime Supporter
Jul 10, 2009
12,629
Houston, Texas
How high is the water level in the skimmer opening? Do you see a vortex in the skimmer when the pump is in crazy mode?
 

Skypalace

Active member
Jun 25, 2020
31
Seattle area
How high is the water level in the skimmer opening? Do you see a vortex in the skimmer when the pump is in crazy mode?
About 2/3 way up. about 2" above level where any air will be drawn into the skimmer. No vortex.

There's no air coming into the suction side. Any residual air (just at pump startup) is pushed back from a bubble I get at the top of the cartridge filter.

Again, this will happen in an identical manner from any of the 3 suction inputs - pool bottom, skimmer, or spa. I don't see how it's a suction side issue. Again, if the pump starts in 'normal' (quiet) mode, full flow and all fine. And pump is instantaneously in normal or goofy mode, well before it's had time to build pressure, draw air in, etc.

I'm 99.9% sure it's something in the pump and/or motor, I just can't figure out what.

I think I've been pretty thorough in checking off both suction side and pressure side issues.

Please watch the video if you haven't, the sound is pretty interesting. And again, zero changes in any part of system (other than pump on and off) will flap back and forth between the two modes, so again I really have troubler seeing how it's a suction side issue, as zero valve or water level or any other changes - like you can see at the :55 mark in the video. Literally no change other than turning pump off and on, and problem completely disappears. Just not forever, 50/50 change whenever the pump comes on.
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
13,703
Pleasanton, CA
Do you have any check valves in your plumbing? A broken check valve on the suction side plumbing could behave that way.

Can you post some pics of the entire setup?
 

Skypalace

Active member
Jun 25, 2020
31
Seattle area
No check valves. Here are a couple of pics.

I'm uploading and will shortly post another ~2:00 video (slow internet so will take me 15 minutes or so). In it, I turn the pump on, all working great, fills pump, good flow. Turn pump off and on, goes immediately into goofy mode. I then (in the video) cycle through all 4 suction side options: A) Both skimmer and pool bottom. B) Pool bottom only. C) Skimmer only D) Spa return. I then turn the pump off and on, and it immediately goes into goofy mode.IMG_2364.jpg
 

Skypalace

Active member
Jun 25, 2020
31
Seattle area
Is that pump running on 110 or 220? If 220 it might have one of the legs not always coming on at start up. Dirty contactor possibly?
It's 220. That was one of my theories (#3 in my original post).

I've of course switched the two-pole pump breaker at the ET control panel on and off, I guess I can pull the electrical access panel off the back of the pump, and test it live in both modes to see if both poles are hot at the pump. Not easy access but I can probably get a couple of multimeters in there when things are cold, then cycle a few times to see what the two hot poles are doing at the pump itself, which will be downstream of any issues.

How do the contacts/switching work at the ET control panel? I assume some form of relay, are those known to be occasionally flaky?
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
13,703
Pleasanton, CA
If you leave the pump running while in the wonky mode, does it shut off or get very hot?

In order for that to be a motor issue, there would need to be a very large load change so the motor should trip the temp limiter.
 

Skypalace

Active member
Jun 25, 2020
31
Seattle area
FIXED!!!! (I think, time will tell)

Thank you @Chad1979, looks like that was the problem. I pulled the wiring access cover on the motor, the rubber gasket was half an inch out of whack. Pulled and reseated the connections, top pole was a little loose so tightened the spade connector a bit, pulled them both on and off a few times, now it's in 'normal' mode the 10-15 times I tried it. Put the gasket on better, buttoned it all up. Tried again a bunch of times, working perfectly so far.

So I guess I was right that it was something at the pump and not plumbing wise. I feel bad that it was on my list of things to check, but bothered you all before I tried it, and it was one of the remaining theories I had that I knew how to test. I procrastinated on that because it's so tight back there (difficult to get head in to see, as well as hands) that I left it until I heard confirmation of it as a theory.

Thanks again TFP team! My first visit but I'll be back! (Already posted another Q about doing Pentair Screenlogic fully wired vs wireless, so I can play with the pool remotely).
 

Skypalace

Active member
Jun 25, 2020
31
Seattle area
Next step was to swap the entire pump assembly, $500, would have worked as I would have of course redone the wiring at the motor, but I'm much happier now. As an engineer it makes me a crazy to not fully understand the root cause of problems. Not a huge fan of 'replace things until the problem goes away' school of repair :)
 

Chad1979

Well-known member
Jul 28, 2019
47
Northwest ohio
Glad to hear that you did find soemthing in the back of the motor wiring block. Its not a common problem to have happen but wires can come loose sometimes. And with it being so random in back to back power cycles with the water flow and valve combinations it seemed like it was at least a good possibility that something was going on with it. Hope it continues to behave for many more years.
 

Skypalace

Active member
Jun 25, 2020
31
Seattle area
Glad to hear that you did find soemthing in the back of the motor wiring block. Its not a common problem to have happen but wires can come loose sometimes. And with it being so random in back to back power cycles with the water flow and valve combinations it seemed like it was at least a good possibility that something was going on with it. Hope it continues to behave for many more years.
With the cover not fully seated, I suspect some moisture got in and got a little corrosion on the connections. Add a not-super-tight connection which probably meant minimal effective contact area, and I guess it couldn't always pull the startup current, so guess the motor kicked into 'unbalanced one-pole 120v mode' with only half the windings powered.

Next time I clean the cartridge filters I'll pull the entire filter assembly, which will give me more room in there behind the motor to do a proper job of getting shiny new connections w/ a wire brush and coat w a little petroleum jelly.
 

Skypalace

Active member
Jun 25, 2020
31
Seattle area
ARGHH!! It's back!

Decided to test it one more time before heading out of town, and it went back into goofy mode. Leaving tomorrow am and don't have time to pull the motor off and do a proper cleaning of the terminals, as well as validate that it's always getting +120 through each of the two poles, which is probably my next step. Hopefully it's this electrical problem, and that wasn't a false fix masking something else...

So turned pool control off, threw the chlorinator floater in there, closed the cover, and hopefully it won't be green when I get back...