Water Level Drops In Pump Basket- Only At Slow Speed

[shane4]

Hi All
Just went through the forum and found something very similar to my issue. However, there wasn't really a definitive answer/solution. The post is about 4 years old so I thought to post my question in a new thread. Originally by "thenateo" April 27, 2020 titled "Pump water level slowly dropping".
I have the same issue. I have used my VS pump for years without issue. Regardless of speed, the pump basket has operated full of water. No air bubbles whatsoever. Last season, I noticed a an air bubble or two of decent size but not concerning. Regardless of speed, the bubbles would not clear. This season, the amount of air at the top of the pump basket is significant. At prime (3000 rpm) it is a swirl of little bubbles. At my typical operating speeds of 1900rpm or 2400rpm there is a noticeable air space but again, not too concerning.
This season though, when the pump runs at 1000 rpm (this lower speed is used over night to prevent the heater from operating but continues to move water) the pump basket water level drops significantly to below the intake. This occurs within 10-15 minutes of the speed dropping to 1000rpm. Never done this before. Always maintained water level. I can not detect any sound of air sucking in (nor blowing out) and everything at the pad is dry. The pump seems to operate and moves water and you can clearly see water flowing out of the intake and falling into the basket. However, this is very concerning that the water level is so low. I can hear water flowing through the heater and filter as if pouring from a jug. As such, there is obvious air going through the system. If the pump is turned off during higher speeds, there is no loss in water level in the pump basket. An air bubble about the size of my palm remains and holds at the top of basket.
To recap: Never had air in pump basket for years. Last year a bit of air is present. This year, a bit of air is always swirling in the basket. When pump is off, a palm sized bubble holds in the basket. When the pump runs at low speed, the water in the basket drops to below the intake quite quickly.
As per picture, the suction side is skimmer and deep end drain coming into one intake at the pump.
Checked these two connection O rings/gaskets all appear good (no nicks, flat spots, dry spots, etc.). Same for the connection at the pump and basket lid.
I cleaned connection surfaces and lubed seals. Clamped everything down.
Picture shows pump off and palm sized air bubble that stays. Water level in basket does not change when pump is off. Only when running at low speed.
Any input, comment, suggestions is greatly appreciated.

 

[Texas Splash]

Everything points to a suction leak somewhere. As your system ages, perhaps some part is not sealing quite as good as it did when original. Perhaps that's related to this issue. Suction leaks can be so small you'll never see a water leak or hear anything at the pad. Hopefully it's nothing on the suction line itself. Also make sure to check the entire line for a potential blockage. The smallest of debris from opening could lodge in the line and create havoc with water flow. Maybe try pushing water backwards from the pump back to the skimmer. Curious though, do you notice any change in the pump pot water level if you clean the filter? Sometimes a dirty filter can present some similar problems.

 

[shane4]

Thanks for the input. Filter has been thouroughly backwashed. I can try backwashing the lines with my shop vacuum like I do when winterizing. Its worth a try. I understand the tiniest of leaks can be the result. And it makes sense if it is the case as undetectedable leaks may be getting worse since last year. I have issues (minor) with the sand filter and have been thinking it's getting close to replacement. I intend to re do all the plumbing at the pad if I do. Just hope the unions coming up from the ground are salvageable. Digging up and making new joints is going to be a pain.
I was leaning to suction side leak too. Just wanted to see if anyone had same thought or other ideas. Will start small and first try new gaskets/o-rings at the basket cover, input and unions coming up from the ground.
Fingers crossed.

 

[shane4]

Made sure contact surfaces were as clean as I can tell. New gaskets for basket lid, connection at the pump's intake and at unions where skimmer and main drain valves are (coming out from the ground). A bit of lube. Clamped down nicely.
Still the same issue. No worse. No Better.
I can not detect a single drop of water anywhere around the equipment and associated piping system(s).
I can not hear any air from the connection points. However, with the pump off and I put my ear right against the pipe section from the ground into the pump, I can hear something. Suction I assume. It is no louder or quieter when I place my ear against the main drain portion, skimmer portion or where the two come together into the pump housing. Makes me think it is coming from further down the line towards the pool????
I am not loosing any noticeable amounts of water from the pool (other than evaporation).
Wish I had a crystal ball rather than stressing over the cost of potentially needing a leak detection test. Only then to have to repair the issue.
Arrrgggg. I hate spending my day off on this Crud!!!
The Joys of pool ownership.

 

[strategy400]

The water level in my pump basket has been low for over a year and pretty much same scenario slow causes air, fast the pump is full of water. I run my pump most of the day, just pausing for 4 hours to avoid peak electricity hours. Typically 1500 RPM to get the SWCG going. At 1500 you can look in the basket and clearly see water pouring in from the intake. I do hear air bubbling fizzing noises when I rotate my cleaner suction valve and more air is introduced into the basket so I suspect my cleaner suction valve has some marginal orings or something. I don't see any such valves in your picture. Maybe the unions are warped a little? It could be debris also. My pump pretty much lost all suction and I reached in and pulled a wad of pine needles out of the impeller area.

 

[shane4]

Update for those who read this thread (and thanks for the input from a few). I narrowed the location of the leak by using the running water over everything method. With patience, an upside down pail to sit upon, a gentle flowing garden hose in one hand and a beer in the other. I ran the pump at a high speed and then dropped it to a low trickle. I can watch as the air space in the pump basket would get bigger and bigger. I'd repeat this multiple times, holding the hose water over a different section of pipe, valve assembly, joint, union, lid, etc. Low and behold, at one spot the air pocket did not grow. Or at least it did so ever so slowly.
Could not pin point the exact leak, but narrowed it down to the small horizontal section of pipe between the pump inlet and the "T" coming from the main drain and skimmer lines. I could see the visible joint cement was blackened and cracked.
Whoever installed my pump did not anchor it to the pad. I assume the constant opening and closing of the basket lid would move the pump itself and helped crack the joint cement that is about 25 -30 years old.
I cleaned up the joints on either side of this pipe by removing the loose cement. I know PVC cement is not a sealant. However, if you can get some into the joint it may re-do it's job of fusing the two pieces of PVC together in the spaces left where old cement has dried, cracked and/or fallen out. So that's what I did. After it set, I wrapped the area with rubber tape type sealer. It worked. A band-aid for now. But it worked.
To make a lasting fix I will need to redo the piping but where the location is, means new unions coming up from the ground. That's going to be pain. I know my sand filter is on it's last legs, so I am going to keep an eye on the temporary fix and when the filter's time has come, re-do all the piping at the pad.
I was tempted to dig up the vertical sections of main drain and skimmer PVC sections to where they meet the underground black poly as I wondered if that could be the issue since I was not able to detect anything around the pad (before the hose water test). I also know a spot where the underground pipe has been repaired with a joint and was wondering if I'd need to check that too.
Where I am, leak detection service is rather costly and then there is still the repair to do.
The running water trick saved all the digging and expense. Glad I am still capable of learning new tricks. The water trick found the area that I was not able to detect whatsoever.

My basket it once again full to the point you'd think it was empty

 

[strategy400]

Awesome. I'm going to do the hose n beer trick!

 

[shane4]

Beer is the essential. Don't forget the beer.

 

[shane4]

For those who come across this thread and think "Hey! That's my issue." Here is a final update. As I mentioned, joint cement is not a sealant. It did not last long. Not sure if it ever worked and it was the rubber so called air tight tape used instead. The tape started to re-position on it's own tension (you need to pull tight when wrapping with it) and it became not so air tight. So I removed all the tape and cleaned up the mess I made with the cement. Ran the pump at a medium speed and applied a narrow bead or good quality 100% exterior silicone caulk. Made sure to get a brand that "promises" it will not hardened or crack over time. Apply to the joint all around the perimeter of the pump and using my finger spread the bead into the joint and creating a seat on either side of the joint. Leaving the pump running will help draw the caulk into the leaks. As I was applying the caulk, the air bubbles were slowly starting to slow down. Left the pump running for a few hours while the caulk almost set. It was still a tad tacky to the touch. I then applied another wider bead all the way around. The tacky texture with the new layer will ensure a nice adhesion between the applications. Spread the caulk to seat such that it overlaps either side of the first application. It has now been about a week and a half and still no air in system. Still, a temporary fix but will do until I get around to replacing that section of pipe with a new joint. For note, there were a few of the tiniest air bubbles every few minutes coming from the bottom of the pump basket. At slow pump speed, these bubbles had enough buoyancy to float to the top instead of being sucked into the pump. I removed the pump's two drain plugs and applied a thin coat of O Ring lube and that problem has been corrected too. Will grab some replacement plug gaskets when around a pool parts supplier. Hope this helps anyone else