Losing pressure

[OKRandy]

My pool pump and I are in an epic battle. So far, I am losing. About a month ago, it started losing pressure and making a loud gravel sound. My friend says it is cavitating. Water flow into the pool decreases significantly when it does this. Well, that set in motion a series of events to fix the problem, but to no avail. We cleaned the filter. A service person inspected the impeller, which was fine. But the neck to the diffuser was completely broken off, so he replaced it. We also replaced and lubed o-rings. A mechanic friend took the motor apart and inspected it; it was fine. He also connected it to his pool and it worked great without any problems. We used a drain king to flush the skimmer and main drain lines, the service person tried to blow them out with high powered air. I also rented a 50-foot drain auger and used it on the main drain line. I really thought it was a clog in the main drain, but now I'm having my doubts. We also used shaving cream and inspected all of the suction side pvc for possible leaks and found none.

Here's the problem: I will prime the pump and start it, and it sounds good and works well. Runs about 20 psi. Then after 20 minutes or an hour or 4 hours, it suddenly drops pressure to about 10 psi and the motor sounds rougher and louder. Water flow into the pool and spa goes down. As time goes by, the pressure continues to drop. However, the pump doesn't seem to lose prime when it drops pressure. No air bubbles in the strainer basket to speak of. I will switch the suction value from skimmer to MD and it doesn't make any difference whatsoever. One potential issue is that it appears the hose to the automatic cleaner in the pool may have leak(s) at some of the connection points. Btw, the pressure seems to go down quicker and more severe when the cleaner is running. However, even if the cleaner is not on, the pressure on the pump still eventually drops from 20psi to 10psi and sounds rough.

Any thoughts, ideas, suggestions are greatly appreciated. Now my water is dark green and if you threw in a few lily pads, it would look more like a coy pond than a pool. Thanks!

 

[tlevy]

I have to say, that is very strange. I can't see how this would affect it, but did you inspect the sand filter too? Did you do a pressure test on the whole system?


68,000litre, IG vinyl, LorentzPS 600 Solar Pump & 1/2 HP Tristar, Sandfilter, Aquarite T-15 SWG

 

[Jimrahbe]

Randy,

Can you send us a picture of your equipment pad, making sure we can see the input area around your pump and any associated valves.

Where does your cleaner get connected?

How many skimmers do you have?

And just a thought... You should not really notice any difference, at the pump, whether pulling from the main drain, skimmer, or both.

Thanks,

Jim R

 

[OKRandy]

I am attaching photos of my pool equipment pad, including a closeup of the suction side.
Cleaner is connected to separate booster pump.
Pool has just one skimmer, and main drain does not appear to be plumbed to skimmer.
Also, I noticed today after letting it run for quite a while after pressure dropped from 20psi to 10psi that there were indeed air bubbles in the strainer basket. Just a few minutes ago, I primed with the pump with 2.5 buckets of water, but I noticed it took longer (probably close to a minute or two) for the water to begin visibly churning in the strainer basket and for the pressure to start building.

Thanks,
Randy

 

[Jimrahbe]

Well, the most likely cause would be an air leak at the pump lid O-Ring. I'm sure you have checked it, but it would not hurt to check it again.

It appears to me that you have three inputs to your pump, one marked as Skimmer and opposite it is the Main Drain, and on the other side of the automated valve is the input from the Spa.

The next thing would do is run your pump using only one of the three inputs at a time... Skimmer alone, then Main Drain alone, and then Spa alone, and see if they all have the same issue.

What moves your automated valves?

Jim R.

 

[OKRandy]

We replaced the pump lid o-ring when we started having the issues a few weeks ago, but I seem to remember at the time that the thickness of the new o-ring seemed slightly smaller than the one I replaced. I ordered the new one online, so I guess there's a chance it is not as thick and is letting in air. I'll try to get a replacement.
Yes, when I run the pump on any of the three inputs, I have the same issue...which seems to indicate to me that it's not a clog in the main drain, right?
When I toggle from pool to spa on my control panel, the automated valves turn automatically before the pump kicks in.
Tonight, the input was on skimmer & MD, the pump lost pressure after about 20 minutes. We re-primed the pump, started it again, pressure started this time around 10 or 11 psi, turned on the cleaner (just to try and do some good while pump was running), and the pressure dropped way down and both the motor and the booster motor (controls cleaner) were extremely hot to the touch.

- - - Updated - - -

Sorry, what do you mean by "pressure test" on the whole system?
Also, I should have clarified. No sand filter, cartridge filter.
Thanks.

I have to say, that is very strange. I can't see how this would affect it, but did you inspect the sand filter too? Did you do a pressure test on the whole system?


68,000litre, IG vinyl, LorentzPS 600 Solar Pump & 1/2 HP Tristar, Sandfilter, Aquarite T-15 SWG

 

[Jimrahbe]

Well,

I'm sill thinking that the Pump Basket O-ring is the issue. Hopefully once you get a new one installed it will be ok.

You are correct about the main drain. Even if it were clogged, which it is not, it would make no difference as long as the Skimmer is working. Having the main drain blocked is no worse than just having the valve turned off.

I suspect that the reason that things get worse when you turn on the cleaner pump is that it is demanding more of the water which is already not available.

Please let us know what happens when you install the new O-Ring.

Jim R.