Pool pump troubleshooting (Solved!)

DaveC426913

Gold Member
17,997
1,592
Well, I'm stumped.
I've got this 1/4HP Hayward pump that simply will not draw water.

I've removed every factor in the system down to the bare minimum, replaced everything in the system that can be replaced and applied silicone lube to everything that can't.

I have a six foot length of new hose sunk into my pool that runs directly to the pump intake (bypassing the pool skimmer and filter).
I've greased the one O-ring on the intake. I've greased the O-ring between the basket and the pump.
I've pulled off the pump head, and inspected the manifold and impeller for debris.
I've checked that the impeller is spinning.
I've taken off the outflow, so it should shoot straight up into the air directly from the pump. When I turn it on, it shoots a half gallon of water up - the half gallon that I primed the basket with - and then barely dribbles after that.



There is literally only 6 inches of system left. From the pump intake to the pump output. It literally will not lift the 6 straight inches from the impeller to the outlet.


The only thing left is to bypass the 6 foot length of hose that runs 2 feet up out of my pool and down 2 feet into the pump. I am sure that, if I opened the basket and poured water directly into the basket, the pump would shoot it out straight up. But if it's just that it can't draw a mere two feet of head from the pool, it's certainly not functioning.

I find the bearings on these things go yearly, and it's more cost-effective to simply buy a new pump every couple of years (~$250), but this year there's nothing wrong with the bearings.

Help.
 
Last edited by a moderator:

Drakkith

Staff Emeritus
Science Advisor
2018 Award
20,476
4,173
Hmmm. The only thing I can think of from having to deal with my own pool pump is to make sure as much of the air is removed from the system prior to turning the pump on. But if you've primed the 'basket' (bucket-like thing with a clear lid?) then you should be okay I would think. I assume the impeller isn't damaged?
 

DaveC426913

Gold Member
17,997
1,592
Even though it's self-priming I expend a lot of effort priming it anyway, just to give it a boost. It's definitely not that.

I went all out and eliminated the last factor in the system. I took off all the hoses and dunked the head of the pump directly into the pool, so it had an infinite supply of water, and zero head.

Nothing.

And yet, the impeller is still impelling!

*don't try this at home. Nothing like holding a 1/4HP electrical device 2 inches above a giant pool of water...
 

JBA

1,313
329
It might be a good idea to check to see whether or not the pump shaft seal is leaking and allowing air to be drawn into the pump by placing your hand on the pump outlet to see if there is any air flow there. With the hose inlet under water, if the shaft seal is tight then you should not be able to feel any air discharge flow.
 

DaveC426913

Gold Member
17,997
1,592
That's got to be it. It's got to be the seal between the basket and the impeller manifold.

It's a funny thing.

When I screw the basket assembly back onto the pump, if I screw it tight, it does not align properly - the basket points down. So I have to back off the threading a half turn till the basket is vertical.

There's a "C-clip" around the throat (see diagram) with notches that are obviously designed to ensure the basket must be properly vertical, and that it won't unscrew spontaneously from vibration. So that makes sense.

hayward-1500-pump.jpg



But it's weird. Unscrewed that half turn, it's almost loose. I do not recall it being loose like that in the past.

Now, that being said, it should not matter to the water-tight seal. ("strainer O-ring" in above diagram). It is not an "end-seal" O-ring; it is a "girth seal" O-ring. This a crummy diagram, but it's just to show how the O-ring is around the girth, in the throat:
Radial-Seal.png


So it should be sealed as long as the male is in the throat of the female.

Still...
 
691
446
I've checked that the impeller is spinning.
If it was pumping last year I don't see how it could be, but a symptom of blasting water from the pump casing, then nothing more, can happen if rotation is reversed.
 

DaveC426913

Gold Member
17,997
1,592
I put teflon tape on the threads, hoping to seal off any air ingress, and I greased the gasket around the manifold - but no joy.

A Video of the output just gurgling. While there may be a tiny bit of air, that's definitely water there. That's just six inches above the impeller.

Yet I can stick my thumb in the basket outlet and feel the impeller whizzing around.
Heck, I pulled the whole basket off so I can see the impeller turning.

No repair has had even the slightest impact on flow.

What's crazy is if I simply pour water on the exposed impeller, it shoots water straight up the outflow. But slap the manifold back together and nuthin'.
 
Last edited:
104
61
I'm with Asymptotic - it sounds as if the pump is spinning backward. You may need to disassemble the pump to be sure of the impeller shape - the rotation direction is correct if the center of curvature (for any vane) is 'behind' the moving vane. If you're feeling more empirical, you could just reverse the motor (assuming that it's reversible). A 'wrong way' impeller still slings, but not efficiently enough to pull in much (any) new water.

Many general-purpose single-phase motors are 'reversible.' That always requires a wiring change (at the motor leads). Is there a prequel which includes some wiring work?
 

DaveC426913

Gold Member
17,997
1,592
I'm with Asymptotic - it sounds as if the pump is spinning backward.
No. You can see in the second video it's spinning counter-clockwise, which is the direction it should be spinning to shoot water out the outlet.

And it does shoot water out the outlet if I pour water directly on it. The water is obviously firing off the right edge of the impeller straight up the outlet.
 
104
61
No. You can see in the second video it's spinning counter-clockwise, which is the direction it should be spinning to shoot water out the outlet.

And it does shoot water out the outlet if I pour water directly on it. The water is obviously firing off the right edge of the impeller straight up the outlet.
I didn't watch the video - sorry.
 
104
61
No. You can see in the second video it's spinning counter-clockwise, which is the direction it should be spinning to shoot water out the outlet.

And it does shoot water out the outlet if I pour water directly on it. The water is obviously firing off the right edge of the impeller straight up the outlet.
OK, I watched the video. I can't really tell which way it's spinning (aliasing), but CCW is obviously the right direction.
 

sophiecentaur

Science Advisor
Gold Member
23,049
3,657
Last ditch stand. Could the impeller be slipping on the shaft? A small amount of resistance / load stops it but it’s momentum carries it round enough to shift a small amount of water.???
 
691
446
OK, I watched the video. I can't really tell which way it's spinning (aliasing), but CCW is obviously the right direction.
Ran it frame-by-frame through VLC, and the impeller appeared to turn CCW in the single frame observed before it blurred to unreadability.
 
691
446
Last ditch stand. Could the impeller be slipping on the shaft? A small amount of resistance / load stops it but it’s momentum carries it round enough to shift a small amount of water.???
Had that happen to me once, although in that case it was a clear polycarbonate impeller, and signs of thermal distress were observable in the hub.
 

DaveC426913

Gold Member
17,997
1,592
Last ditch stand. Could the impeller be slipping on the shaft? A small amount of resistance / load stops it but it’s momentum carries it round enough to shift a small amount of water.???
I thought of that. I can apply pressure to it directly with my thumb and it seems pretty determined to keep spinning.
 

DaveC426913

Gold Member
17,997
1,592
OK. Problem solved. And of course it's me being foolish.

It turns out that the hose running out of the pool has a leak at its fitting:

33351.jpg

Even though the hose was seated in the drain with teflon tape, the leak is several inches up, between the hose and the fitting.

I kept checking to ensure the overflow was full, and filled it frequently. So because the overflow wasn't draining of water, I had ruled it out as a source of a leak.

It sits in only 4 inches of water, enough to get a water lock, but the leak is up at the top of the fitting, so every time the overflow drained by just an inch, air was seeping in there. And that had not occurred to me.

I thought I had conclusively ruled out the hose as the problem when I short-circuited it directly from the pool - bypassing this connection completely. But I guess that test wasn't as conclusive as I thought.

Thanks guys for all your assistance. I never would have kept at it if you guys hadn't been filling me full of ideas to try.
 
Last edited:

sophiecentaur

Science Advisor
Gold Member
23,049
3,657
PF (at least me) loves this sort of brain teaser. Glad you have closure.
I was about to suggest that the motor was running in reverse - I was that desperate for an answer.
Anyway - well done.
 

DaveC426913

Gold Member
17,997
1,592
Several good things have come out of this:

1] I have learned the value of keeping the seals lubed.

2] By adding a threaded union fitting under the overflow basket, I can now detach the hose from the overflow basket and dunk it right into the pool.

3] I just figured out that I don't need to run fresh water into the pool to keep the overflow filled (to preserve a water lock). Running fresh water means it needs to be babysat. (Too often have I forgotten the water was on.) Instead of fresh water, I simply run my sump pump from the pool into the overflow. Now I can circulate the whole system, including the filter without having to fill the pool to operating level.

4] I'm much more confident now that I can disassemble and maintain the whole system. (I mean, I was good before, but this was a real win. Solved many problems that have plagued my system over the years.)
 
Well, I'm stumped.
I've got this 1/4HP Hayward pump that simply will not draw water.

I've removed every factor in the system down to the bare minimum, replaced everything in the system that can be replaced and applied silicone lube to everything that can't.

I have a six foot length of new hose sunk into my pool that runs directly to the pump intake (bypassing the pool skimmer and filter).
I've greased the one O-ring on the intake. I've greased the O-ring between the basket and the pump.
I've pulled off the pump head, and inspected the manifold and impeller for debris.
I've checked that the impeller is spinning.
I've taken off the outflow, so it should shoot straight up into the air directly from the pump. When I turn it on, it shoots a half gallon of water up - the half gallon that I primed the basket with - and then barely dribbles after that.



There is literally only 6 inches of system left. From the pump intake to the pump output. It literally will not lift the 6 straight inches from the impeller to the outlet.


The only thing left is to bypass the 6 foot length of hose that runs 2 feet up out of my pool and down 2 feet into the pump. I am sure that, if I opened the basket and poured water directly into the basket, the pump would shoot it out straight up. But if it's just that it can't draw a mere two feet of head from the pool, it's certainly not functioning.

I find the bearings on these things go yearly, and it's more cost-effective to simply buy a new pump every couple of years (~$250), but this year there's nothing wrong with the bearings.

Help.
A centrifugal pump does not suck water into the impeller. The impeller must be flooded and no air in the feed pipe or hose in this case. A hose has a large pressure drop. Better to use pipe with no elbows if possible. For example, a well pump has to have a check valve or foot valve at the bottom of the well to keep the inlet pipe full or the pump will not push water.
 

DaveC426913

Gold Member
17,997
1,592
A centrifugal pump does not suck water into the impeller. The impeller must be flooded and no air in the feed pipe or hose in this case. A hose has a large pressure drop. Better to use pipe with no elbows if possible. For example, a well pump has to have a check valve or foot valve at the bottom of the well to keep the inlet pipe full or the pump will not push water.
These pumps are self-priming.
 

Want to reply to this thread?

"Pool pump troubleshooting (Solved!)" You must log in or register to reply here.

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving

Hot Threads

Top