Hi Jin2008- I know that this can be very frustrating, as I had a similar issue last year.

What's your setup? Submersible or external pump, priming pot, etc? The more info you provide, the more someone here will be able to help.

Good luck...

bwalter, thanks a lot for the quick response.

Let me try to describe my setup, even though I am really not that familiar with the whole system ( I inherited this koi pond from the previous homeowner and for quite a while,it really has been problem free till now ).

The pump is external. There is a little cascade water fall right above the koi pond. There is another pipe also above the koi pond, so when everything is normal, the water comes out from both the pipe above the pond and the waterfall.

Yes, there is also a priming pot that is connected to the pump through some pipes. The priming pot is plastic, everytime, when I tried to turn back the pump, I filled the priming pot first and then turn on the pump.

Some portions of the pipeline is also buried underground.

My pond is roughly 10x10.

Please, please help me!!!

jin2008,
A few more questions.

Is the pump running at all times?
Can you hear the pump running for sure?

Is the pump becoming extremely hot to the touch?

It could be a loose impeller causing the flow to stop?
Take the end of the pump and check the impeller, to find out if it is loose or worn?

Is the pump losing it's prime continuously?

Is the water level dropping in your pond, before you lose the circulation??
"Horton"

Horton,

I think the pump is running at all time, we always plug it in and never shut it down intentionally. I can hear the pump running ( even though I don't know if it is really working properly ).

I think the pump might be hot, I haven't really touched it ( will do that right after I get home tonight ), but I did notice that the water in the priming pot is very hot ( we are in California, still it gets pretty cold during the night, I don't suppose the water to get so hot ).

I don't really know what impeller is, could you please let me how I will be able to check if the impeller is loose or not ( how will I be able to identify which component is an impeller? )

We now constantly don't have circulation, is that what you mean by pump losing its prime continuously?

Yes, the water level did drop abnormally before the first time we lost circulation.

Do you have any idea what might be the problem?

Thanks a lot for all the help

jin2008

jin2008, you said, "Yes, the water level did drop abnormally before the first time we lost circulation."

That points to a leak in the plumbing somewhere and consequently, an air lock develops in the piping or there is a loss of prime to the pump, either of which, would stop the pump from pumping the water around.

You will have to find out where that water is going and fix the leak?!

The impeller is the part of the pump that pushes/pulls the water through the pump. It is similar to the blower on a hair dryer, but instead of pushing out air it 'pushes' the water around your pond's plumbing system.

Should the impeller become loose/damaged, inside the pump housing, it can stop doing it's job of circulating the water.
I do not believe that it is the impeller that is causing your problem. But it is as well you know what the impeller is and the job it does.

For the present, I think you have to find where you are losing that water.

Switch the pump off [or unplug it].
Fill your pond up to the normal depth.
If you are using chlorinated water to top up the pond, use a de-chlorination treatment, [can be purchased at a pond supply store] to treat the water. An overdose of chlorinated city water, could injure or kill your fish.

When the pond is filled up again, leave the pump off and see if the water stays up to the normal level.
Give it a few days if necessary, to see the results.
Check around the perimeter of your pond for wet soggy areas.
I'm wondering about just how much water you did lose?
How far the level went down?

If the water level does not go down, without the pump running, then turn it on and check all the piping/hoses etc for breaks, splits loose connections, etc, to determine where the water is escaping.

Let us know what you discover.
"Horton"

jin2008, I forgot one important thing for you to to look at.
Make sure the priming pot lid is fitted on tightly.
If air gets sucked in there, because the lid is not fitting properly, the pump will stop circulating the water.
"Horton"

Horton,

Mmmh, first, I think if there is a leak, it should be the pipes somewhere. This is because every since my circulation stops frequently, I don't notice the water level droped ( this has been for almost a week now). The difficulty now is that as I mentioned, a part of the pipeline is buried underground. Is there anyway to diagnose leakage without digging up everything?

Also, I am going to buy a air pump right away so that my kois will not die suffocated. Will it help me situation temporarily ( I guess it will take a while for us to have this resolved ). Also, what am I going to do with filtering? Should I still feed the fishes at all?

Many thanks

jin2008, sounds like it is in the plumbing and really there is no easy way, that I can suggest to you, to finding the break.
It is just to search inch by inch, fitting by fitting until you find it. I hope it is above ground, but since you have not mentioned seeing any wet areas above ground, you may have to start digging?
The air pump is a great idea, I meant to suggest that to you in the previous posts. That should help with the aeration.
The quicker you find and repair the break/leak the quicker you can get your filtration back on.
Or you could buy a small submersible, to pump the water around via a temporary hose, to your filter, until you can get at the problem.

As far as feeding goes you could cut down, without doing any harm to your koi. They will survive on what they can find to eat in the pond.

Keep in touch.
"Horton"

Horton,

I found the first leak. Please see the picture below from the link. I can see water dripping down from the red nob. This part of the pipe is connecting the priming pot with the pump ( the pump is actually below this ). Do you know what this nob is and what this is for? It seems I can turn the nob, but everytime I turned it, the leaking seems worse. Do you or anyone know how I will be able to fix this leak?

Thanks again for everything.

Here is a link that might be useful: picture of the nob that is leaking

jin2008, that is a ball type, shut off valve, probably situated there, so the pump can be removed,if necessary.
It is difficult to see it all exactly, it could even be a by-pass shut off. Anyway if it is leaking, it should be replaced.
You are probably losing the prime at that spot? Though there could be other leaks in your system??
The only way to remedy that, is to install a replacement ball valve and go on from there checking the whole piping run.
"Horton"

Jin2008,
Horton is correct in that the valve that is leaking is a ball valve. It is hard to say from the picture what the valve does but I would guess that it is a bypass to the filter or it runs another piece of equipment. That could be why the pond is dropping but that is not why the pump stops pumping. That valve is on the output of the pump and I would say that you are looking for something on the inlet side of the pump. From the picture your pump looks like an older Sequence 1000 pump. Since you don't loose prime all the time I would say that the flow from the pump is being reduced so the pump can't move enough water though it to remove the air. This could be a restriction on the intake or the output. Since you are loosing prime quickly I would try a few things that won't take long. First check the primer pot when the pump is running and see if you see a lot of air bubbles in the pot. Check where the pump sucks water from the pond and see if it is clogged. Next you said that the flow out of the pump is slower so that could be a blockage on the input or output. So on the filter move the multiport valve on the filter to the recir position and see if the flow increases a lot. If it does than the filter is clogged. Also what type primer pot do you have? A picture would be nice. A lot of the older sequence pumps used a Hayward primer pot and the Orings on them tend to leak unless the Oring is replaced once every year or two.
Mike

First of all, thanks a lot for everyone who replied. Your comments and suggestions are all so helpful...

Now, looks like I might have quite a few issues here. Let me summarize:
1. I definitely have a leak in the ball valve.
2. I might have a clog somewhere, either the filter or the pipe inside the pond which extract the water from the pond for circulation.
3, I might have a leak in the oring of the primer pot
4, my pump might be dying.

I plan to see if I can help with the clog issue first, since this might be the direct cause of my lose of circulation. For the pipe in the pond, how would I be able to get rid of the clog? As you can see from the picture, the pipe is horizontal, long and thin, if it is clogged? What should I do to clean it?

If it is the filter, I have to confess, I have never cleaned this filter before, don't know even how to open it, what should I do to get rid of the clogging issue?

What is the oring of the priming pot? Is it in the lid? I actually, I don't recall seeing an o-ring everytime I open up the lid though, is it adhered to the lid?

Again, thanks a lot for everything.

Jin2008,
I am sorry but when I first looked at your picture I didn't notice that there was three other pictures. From the other three pictures I can see that you do indeed have a Hayward primer pot. That could easily be where your air leak is. As to where the oring is located it is in a grove on the lid. When you remove the lid it is located on the side of the lid about a 1/4" from the bottom of the lid. Another thing that I noticed in the other pictures is it looked like the seals on the pump maybe leaking. Normally this would leak water out of the pump but if the intake was clogged the pump would create a lot more vacuum and that might cause the pump to suck air in through the seals. Of course I could be wrong about the seals as it is hard to tell by looking at a picture that was shot at quite a distance. But enlarging the photo it looks like the shaft on the motor between the volute and the volute looks rusted. Since none of the bolts look rusted than the source of water that caused the rusting didn't come an external source but probably from water leaking at the seal. Which could also be where you are loosing water. Unless the valve is leaking bad I don't think that this would add up to the water that you are loosing. The valve is probably dripping and it takes a little over 86,000 drops to make up one gallon of water. If it was dripping at the rate of one drop per second it would take about one day to loose a gallon. Another thing I saw in the photo is that you have slide handle valve on the filter and no way to put it in recir. That there is no pipe draining from the backwash port on the valve so I don't know if you are back washing the filter. I could not tell what filter you have and with the way the flow water through the filter is valved it could easily be a sand filter. In which case the sand could and probably is clogged. The one thing that I could not tell by the pictures is if the pump is a high pressure pump or a low pressure pump. But looking at the plumbing I would have to guess that it is a low pressure pump that would have a very tough time back washing any kind of filter with out an air assist. On the other side of the pump that can't be seen from the pictures it will have a metal tag on the motor. On this tag it will tell you things about the motor such as the hp of the motor and weather it runs at 1725 or 3450 RPM. This would tell me an awful lot about the pump. Also if you know what type of filter you have and the maker of it that would help.
Mike