Pump Losing Pressure - Need Additional Ideas

[gwater]

Hi there,

Had an issue happen with my pump's ability to keep prime and draw in water randomly in late February, and have been trying several fixes - all with no luck. The next step is the pool company is pushing for an $800 leak testing, which I am working to resolve on my own before it gets to that point. 13k gal inground saltwater pool, with two large live oak trees above and around the pool - so the pool gets tons of droppings and debris . We had some good freezes in February, but I had the pump running 23 hours a day so nothing should have frozen and cracked. I have tried many common fixes, all with no luck so far, which is why I am seeking y'alls wisdom.

Issue: Pump does not draw in enough water, loses prime, and pressure is lost in the system, with zero pressure in the filter. My pump is a TriStar VS 950. No noticeable water leaks around pump, and water level was never low at the time of malfunction.

I have tried several things so far to resolve this, all without luck:
1. Filter cartridges cleaned
2. Skimmer line has been blasted with both a hose bladder and with CO2. No blockages. Pool guy was not able to blast the line between the floor main drain to the skimmer basket (two pipes in the skimmer basket - one from main drain to skimmer basket, and the other from skimmer to pump as I understand it) - so we do not know if that is a potential issue or not.
3. Replaced and lubed housing o-ring
4. Replaced and lubed pump basket lid o-ring
5. Replaced filter pressure gauge
6. Impeller has been cleaned - no blockages detected (although I have not fully taken apart the pump to observe the impeller from the inside)
7. Every time I attempt to prime, I fill the pump basket to the top. It immediately goes down to the lower level shown in the picture below. I also open the pressure gauge on the filter so that I can bleed out air. No air comes out during the priming process.
8. I have even tried to prime the pump with a hose shoved down the skimmer basket, and that does not lead to extra waterflow into the pump basket while priming


If you guys have any advice, I would greatly appreciate it. I'm about out of ideas besides replacing every o-ring and gasket in the pump.

Thank you very much for your help!

Picture #1 = photo inside pump basket while trying to prime, the water level starts full (after I fill it) but is brought low in the basket and a small amount of water is coming in from the skimmer basket line. Picture #2 = my equipment setup (the old robot cleaner motor is on the left, this is no longer used as we have a dolphin now).

 

[ajw22]

Welcome to TFP.

Take apart the pump and fully check the impeller.

 

[Jimrahbe]

G,

I agree with Allen...

It sounds like an impeller problem to me...

Thanks,

Jim R.

 

[gwater]

Great thank you both! Once we get a break from this rain here in North Texas I will give it a go.

 

[gwater]

I have taken it apart but the impeller is clean. There is a small chip on one of the blades though which I show in the picture below - I don't think this could be the issue but I figured I'd flag it.

Do you guys have any further ideas? Nothing has looked out of sorts so far.

 

[PoolStored]

Clean, inspect and replace if necessary, the union on the suction side of the pump.

For more see this:

Pump Basics - Further Reading

www.troublefreepool.com

 

[gwater]

Clean, inspect and replace if necessary, the union on the suction side of the pump.

For more see this:

Pump Basics - Further Reading

www.troublefreepool.com

That's a good shout, thank you. I have inspected and cleaned - looks to be in good shape. I will apply lube before putting it back together

 

[PoolStored]

See that link for other potential issues and solutions.

 

[Lake Placid]

How thin are the blades on the veins of the impeller? How was the diffuser condition? Warped…worn?

 

[gwater]

Going to replace the impeller - blades seemed thin, and one had a good chip in it. Diffuser looked in good condition, no concerns there.
I also noticed one of the drain plugs looked to be in below average shape, so I will replace that too. I will also replace the union gasket coming in to the pump. Once these new parts arrive, I will try again. Thank you all for your help so far. Unfortunately, nothing glaring so far, but hopefully these replacements and fresh lube on all gaskets will help. Thanks again

 

[PoolStored]

Replace the o-rings on the drain plugs.

 

[bradgray]

I will also replace the union gasket coming in to the pump.

You most likely have a leak on the suction side, as many have suggested. A worn or loose impeller may fail to 'build' prime but it sounds like it draws the initial gallon through, it just chokes on air rapidly thereafter.

You don't have any valves, so this really only leaves the items you've already addressed, the pump housing, or the plumbing.

You've confirmed the clear lid on your pump is not cracked? Does not have deviations in the channel where the o-ring rests?

Inspect everything that seals the pump in front of the seal plate. Run the pump for a moment, ideally building that a moment of pressure, and shut it off - listen for whining/high pitched air escaping near mating surfaces and pipe welds.

 

[gwater]

You most likely have a leak on the suction side, as many have suggested. A worn or loose impeller may fail to 'build' prime but it sounds like it draws the initial gallon through, it just chokes on air rapidly thereafter.

You don't have any valves, so this really only leaves the items you've already addressed, the pump housing, or the plumbing.

You've confirmed the clear lid on your pump is not cracked? Does not have deviations in the channel where the o-ring rests?

Inspect everything that seals the pump in front of the seal plate. Run the pump for a moment, ideally building that a moment of pressure, and shut it off - listen for whining/high pitched air escaping near mating surfaces and pipe welds.

You are exactly right - it pulls in that initial gallon of water, but then chokes on air. Good observation, as that rules out a few things.

The clear lid did look normal, but I bought a replacement lid and might as well throw that on there just to see if it helps.

I will run the pump and if it is still struggling, I will use hose down some of the connections, or cover them with a plastic bag, to see if that stops the system from drawing in air. Thank you both for your help.

 

[gwater]

I replaced a few more parts and ran the pump last night, still with the same issue unfortunately - pump will draw in the first gallon of water, but will then the basket water level will not remain full, it remains only 1/3 full and it sucks air. In addition to the list of repairs in the original post, I have also completed the below:

1. Replaced drain plug O Rings and lubed
2. Lubed diffuser O Ring
3. Replaced and lubed both union gaskets
4. Replaced impeller
5. Replaced pump basket lid, and lubed O ring

Three observations from trying to prime it up again:
1. With the lid on, and pump off, I noticed some occasional air bubbles in pump basket coming from the red path in the screenshot below. I think this helps narrow down where the air leak could be coming from. No observed water leaks below or around the pump while it is operating


2. When trying to prime, the filter is not building up any pressure. With the pressure air gauge on the filter open, no air is bled out.
3. When trying to prime, I feel a lot more air blowing around this section (circled in blue) of the pump on the right side (top down view). There is much less airflow on the left side of the pump in this area. I know the pump blows out air as part of its normal operation, but this area on the other side of the pump has much less noticeable airflow



If you have any further troubleshooting ideas, please let me know. The above ground plumbing has no noticeable defects. My next tests will be to wrap certain areas of the pump/plumbing with grocery bags to see if that limits the air coming into the pump, which would help me pinpoint the location of the breach. I also may run the pump with the filter cartridges removed to see if the system can move water there, and if it will, I would replace the cartridges (which were recently cleaned).
I really appreciate your help here.

 

[Rancho Cost-a-Lotta]

What's happening inside of the skimmer basket when the pump is trying to prime?

How far away is your equipment pad from poolside?

 

[gwater]

What's happening inside of the skimmer basket when the pump is trying to prime?

How far away is your equipment pad from poolside?

water remains still - there is little suction in the basket. Originally, if there were leaves in the skimmer area, it would get sucked down to the bottom of the basket. Since this issue has arisen, the leaves remain floating in the skimmer basket and are not pulled down.
Equipment is roughly 20 feet from the skimmer basket and ~8-10 feet from the pool

 

[Rancho Cost-a-Lotta]

If it was my pool...

I would try to prime while running booster pump. If it makes no difference, cap it off.

Last resort, I would try running a hard line from the pump directly to poolside. It sounds like it would only take about two 10 ft sections of pipe and a few fittings to make it work. This would rule out or confirm a leak between the skimmer and pump.

If my ideas get vetoed by the experts, no hard feelings.

 

[BillyMac96]

If it was my pool...

I would try to prime while running booster pump. If it makes no difference, cap it off.

Last resort, I would try running a hard line from the pump directly to poolside. It sounds like it would only take about two 10 ft sections of pipe and a few fittings to make it work. This would rule out or confirm a leak between the skimmer and pump.

If my ideas get vetoed by the experts, no hard feelings.

Exact same thing was happening to me, that's what i did...Hard line from after filter, but before return to pool...flow was great and it caught prime. Now leak detector dude did say and show me how my return line was corroded from choline where it turned from a hard line to a flex pipe, after it caught prime i did return to main return line and things seem back to normal...day 2..now i'm still gonna give it few more days before i glue everything back.

New video · Monday, May 12 ð¬

Tap to view!

photos.app.goo.gl

 

[gwater]

If it was my pool...

I would try to prime while running booster pump. If it makes no difference, cap it off.

Last resort, I would try running a hard line from the pump directly to poolside. It sounds like it would only take about two 10 ft sections of pipe and a few fittings to make it work. This would rule out or confirm a leak between the skimmer and pump.

If my ideas get vetoed by the experts, no hard feelings.

Thank you for the help here. The booster pump did not make much of a difference, however it did help provide a little additional flow which turned on the Pentair Intellichlor Salt Cell (when trying to prime, the pump does not produce enough flow to turn on the salt cell).

That is a great idea on running a hard line, and thank you @BillyMac96 for the video - both are very helpful. I am going to try this, both from the pool to the pump, and then remove and try from the filter back to the pool. I tried this morning and didn't realize I needed the special Hayward union fitting to attach to the pump, so that should be here this weekend.

 

[Rancho Cost-a-Lotta]

I have the Pentair pump and it will accept a standard NPT threaded male fitting. Double check your pump, as you may not need to purchase a union.