Pump losing prime

[jdale]

I'm in the process of converting a pool to a pond. I replaced the pool pump with an Elite 800 with priming pot -- an external pump. It draws from the skimmer, goes through a check valve, returns through a waterfall. It's been running ok for a few weeks but now it is losing prime very quickly -- hours or even minutes. When I fill the priming pot, it stays full, but once I start the pump up I can see the level dropping in there. At that point, if I shut off the pump, it continues to drain (from the outflow side, not back through the check valve).

So far I have cleaned out both the skimmer and the leaf basket in the priming pot, used o-ring grease on the o-ring in the priming pot lid, and snaked the lines both from skimmer to pump and pump to waterfall. Everything looks ok, no obstructions. The water level in the skimmer looks okay as well, I'm not seeing it emptying when the pump is running.

Seems similar to this thread but I think I've gone through all the idea there: https://www.gardenpondforum.com/threads/i-need-some-advice-fast.10850/

What else should I be checking? Thanks for any ideas.

 

[sissy]

welcome did you check the check valve as they get dirty and plugged up

 

[sissy]

I do not have an external pump but saw it on one of the pond video's on you tube

 

[jdale]

Thanks Sissy. I did actually remove the check valve entirely when I snaked the line (otherwise I figured I wouldn't be able to get the snake through it). It's clear. But a good thought.

Any more ideas?

 

[randythawkins]

When you say that it is losing its prime is that to mean that air is entering the area? in a closed system that should not happen and priming the pump is an effort to remove as much air as possible so that the pump can move water. if air is entering then there is a opening of some kind. My pump is not one I have to prime but early on when I first started my system running I noticed air trapped in the pump's basket (it has a clear lid). It was not affecting things that much but I was getting air out of my lines at the pond and it never cleared out. That meant somewhere air was entering the system. In short I traced it back to a stand pipe I have right where the skimmer's opening is located. Even though it did not look like it air was being pulled down the stand pipe (when looking in the pipe I could see the water spinning in a vortex shape and I guess air was eventually being captured at the bottom of the vortex and pulled through the system). I placed a tight fitting PVC cap over the stand pipe and immediately the air in the pump's basket cleared out, being replaced completely with water, and no more air was coming out of the pond end of the lines. Plus the noise coming from the pump dropped significantly too. (In the attached picture, the pipe comes out of the back of the skimmer and into a vertical pipe. The top part of that vertical pipe I kept open so that I could have access to the line if I needed to snake it. It is that top par of the T that I capped off.)

I am not sure what snaking the line would achieve...I don't think this is a water flow issue. Even if it were if the pump is primed and there is not air and you shut everything down the water should just sit in the system. Someone correct me here if I am wrong but I think you need to figure out how air is entering the lines. Maybe shut it down and dry off everything around the leaf basket lid and watch for water leaking out. If there is one I don't think the water would leak out as fast as air was getting pulled in so it may take awhile.

Does any of my babbling make sense?

 

[jdale]

I do mean that air is entering. The priming pot / pump basket has a clear lid like yours, and when I look in there, the water level has dropped, which is the same as saying there is air getting in (displacing the water). The question is why....

I have seen when the water level is very low in the pond, I get a vortex like you describe in the skimmer, lots of air gets into the pump, and it shuts down. Solved by raising the water level in the pond. I'm not seeing that vortex now so I don't think it is the issue. Although maybe I should raise the water level anyway just to be sure. After the skimmer, there are no other openings in the pipe until it gets to the priming pot. It goes underground a few feet, comes back up and goes directly to the priming pot.

I am not seeing any meaningful water leakage. A few drops here and there. There could still be leakage above the water level, like on the lid of the priming pot / pump basket, or maybe where the pipe connects to that. Although those particular items I have gone over. Could be the join between the priming pot and the pump itself maybe? Apparently whatever it is only leaks when there is the pressure of the pump running. I was also thinking it could be a jam in the pump itself, but I think you are right that it must be air coming in, so that's probably not a possibility unless the pump chamber is somehow not sealed properly.

I do see some air bubbles coming up in the waterfall basin though. So that implies there is air getting in somewhere in the system.

 

[randythawkins]

Process of elimination...first get rid of the vortex. Maybe that is as easy as rising the water level. Do and and confirm no vortex. If you still have the same problem then maybe it is around the lid. 2 points - (1) the air is entering before the pump basket or you would never see it in the basket. I say that because the pump would force any air down stream and since you see it in the basket it must be before the basket or the basket itself. (2) you mentioned a few drops around the lid. That was with the system not running, right? If so when it is running it will pull air in with more force than the water leaks out. In my situation I have a good 20' of run between the vortex and the pump and it was able to pull air that far. I am still amazed by that. My point is if was leaks out slowly when no force then air could get pulled in with a strong force. If it were me some thoughts I would try....be sure the lids runner gasket is clean of the smallest grain of sand, lube it up some with petroleum jelly, maybe even lay some Saran Wrap around the lid and see if it get a suction pull on it. Not sure how well that would work but worth a try.

 

[snoozer]

I don't have an external pump for the pond but when we had an above ground pool there would be times that the pump for the filter would lose prime. It was usually some dirt or sand on the gasket. This is just enough to break the seal and it starts pulling in air.

 

[jdale]

Thanks. I did clean the o-ring off (twice now), and there was some grit. It's been better since but still not great. 12 hours, 24 hours, most recently it made it a few days. So at least it is getting better again rather than progressively worse.

I also pulled the drain plugs and gave them teflon tape and o-ring grease on their o-rings, and tightened the hose clamps on the check valve. In the spirit of trying to secure as much as possible. We also had a lot of rain, so the water level is up, and that might be helping as well.

I'm reassured by what you say about the air needing to enter before the pump basket. I did wet all the joints in the plumbing that are accessible (not buried) to see if I could see air getting sucked in, but it looks fine.

I also have now twice found the pump running, but not actually moving anything. No water or even air reaching the waterfall filter, and the pump basket actually still had plenty of water. Again, the pump basket is clear. Maybe there's an underlying problem with the pump that I am not thinking about? Simply losing suction for some other reason? Not sure what would do that.

 

[randythawkins]

I also have now twice found the pump running, but not actually moving anything. No water or even air reaching the waterfall filter, and the pump basket actually still had plenty of water. Again, the pump basket is clear. Maybe there's an underlying problem with the pump that I am not thinking about? Simply losing suction for some other reason? Not sure what would do that.

Pump "running" but no water moving and no air in the basket? Sounds like the impeller has come lose from its shaft. In other words the motor is turning but the impeller is not. Thoughts???

 

[jdale]

Makes sense, but would it connect and disconnect?

Is this a DIY thing to open it up and fix? Owner's manual here: http://www.elitepumps.com/manual_elite800.pdf
Would I have to redo the sealant, or will it reassemble ok as long as the o-ring is in place and I don't pull apart the ss seal? I have not poked around in one of these before.

 

[snoozer]

Have you tried calling the manufacturer? They may have support folks who could give you some guidance. I usually take a chance on fixing things figuring it already isn't working so what do I have to lose. Of course, I have sometimes started taking something apart and decided I would be in over my head and put it back together. I call the neighbor who can fix almost anything and he shows me what to do. If you weren't so far away I would send him over.

 

[randythawkins]

I believe I will sing along with snoozer. I was also going to suggest contact the manuf and see if they have some helpful information. Also maybe a quick google search with the pump's model number and see if some helpful results come back.

I looked at the PDF manual you provided and believe I need to take back my theory of the impeller slipping. Reading the manual I learned that the impeller threads onto the shaft so, outside of catastrophic failure, if the shaft is turning then the impeller would be also. The thing I find interesting is the sporadic nature of the problem. I guess if someone held a gun to my head and told me to throw out another theory it would be that the motor is not consistently turning the shaft at proper speed. I don't know much about motor operation but maybe the Volute is packed with algae bogging down the impeller, maybe a bad seal which prevents fluid rotation of the shaft when it comes through the Bracket, or maybe the bushings on the motor are dirty causing greater resistance which might results in a slower turning motor? You might be able to easily check for algae bogging the impeller but the others would need to be checked with the manufacturer.

 

[jdale]

I have sent them a note. If I don't get a response I'll give them a call.

I will say, now that we are back to at least running for days, the water is looking the best it ever has. I spotted tiny, tiny tadpoles in the waterfall (they would have had to go through the pump to get there, possibly as eggs) and then when I looked discovered there are larger ones all over the pond walls. If even 1% survive there will be a bumper crop of frogs... Not sure if they are all the American bullfrogs we have in the pond or maybe tree frogs, there are a ton of those around the house as well.

 

[snoozer]

Good luck with the pump and the frogs.