Carrie, my Skippy has the outlet pipe on the opposite side of the tank from the drain. I saw no benefit in blocking access to the most efficient way of removing water and debris from the tank. The vortex effect you mention does not simply move crud from the front of the tank and deposit it at the back of the tank. Debris is evenly distributed around the bottom of the tank with some being deposited up the sides of an oval tank to equal that deposited at the ends by centrifugal force. The swirl is created by the 45o to 90o elbows at the ends of the arms of the T. Skippy Stuff had a good picture of this. I leave the pump going so water continuously circles as it exits the pipes at the bottom of the tank. That 45o to 90o angle at the ends of those two pipes is what creates the vortex. Without the angle, the water does not swirl. The most efficient position of the angles is to give it a flat horizontal flow. The water exits the tank through the drain hole, taking with it a majority of the debris from the bottom. I usually spray the sides of the interior with the garden hose to get more debris flushed out. It won't bother the bacteria if you keep the spray on the walls and not directly on the filter material.

When you think enough water for an exchange has been flushed you can replace the plug. I always add a new strip of Teflon tape so it is easy to remove and replace the plug. I don't usually bother to reduce water flow to replace the plug but you might want to do it that way.

Here is a link that might be useful: {{gwi:206032}}

I neglected to mention an important addition I made to my Skippy design after power outages caused all the debris collected in the Skippy tank to backwash into the pond. Since this is undigested mulm (rotting fish food and poop) it was a disaster. The pipe crossing the top of the Skippy is where the water from the pump enters the tank. This is where I inserted a T connector with the center leg pointing up. This allows a break in the water flow and prevents any backwash. You can place a cap on it so long as the cap has a hole in it. If you put a straw through the hole in the cap, air will be drawn into the water flow increasing the oxygen content of the water and improving the bacterial action in the filter material. The end of the straw on the inside of the cap should be pointing downstream to the flow. You can hear a slight whistle if it is working correctly.

Sleepless,
My inlet is the exact same as the link you showed, except it's a 300 gallon instead of whatever size they showed.
Where the plug outlet was I replaced it with a line that valves into my pump. I use the head from the Skippy (which is located above my pond) to prime the pump. I can also pump the water from the skippy into the garden if I want to.
My pump is on continuously also.
What I'm thinking of doing though is removing the vortex and instead pushing all of the water from the back of the skippy towards the front so I can push all the debris towards the drain for easier removal. So that I can push the bad stuff out of the drain to clean instead of taking all of the filter media out to use a hose to push it towards the drain.

In my new design instead of the pipe going to the middle of the skippy and splitting into a vortex, it would go to the back of the skippy and have 3 or 4 90s pushing water towards the drain plug.
Is there a drawback to that? I know the vortex is useful in theory, but I don't think it gives enough of an even flow through the skippy to justify keeping it.

Meant to add- the line that runs from the drain of the skippy to my pump stays off at all times UNLESS I am trying to get solids out of the skippy OR priming the pump after it's been off.

I think you will be disappointed in the results. What you will get is a constant churning that doesn't allow the mulm and other solids to settle out. (Sort of like trying to separate eggs when they are already in the blender.)Then the water passing through the filter will be so thick with gunk it could suffocate the bacteria. The water leaving the tank will be just as dirty as it was when it went in. If the aerobic bacteria no longer function, then anaerobic bacteria will take over and the water will start producing smelly gases. Even a gentle circular pattern can settle out an amazing amount of debris.

If your water is brown despite water changes, I would suspect a contaminant like leaves and twigs on the bottom. Another possibility is peat in the soil your plants are in. Do you have rocks on the bottom? That could be a contributing factor. I had a terrible problem a couple of years ago when the raccoons went bonkers and dumped several large pots in the water. I had to keep on dredging because I couldn't see them and it took most of the summer to find the last of them. It was worse because the mud and fine stones in the soil wrecked the pump. When the problem is staining in the water you need to use activated carbon in the flow of the water. It won't help though if you are dealing with large quantities of rotting leaves or mud. Fill a glass jar with pond water and allow it to sit for a couple of hours. You will be able to see better what is circulating in the water that makes it brown.

There aren't any rocks in the bottom. My water lilies have our dense red clay in the pots. It was the only thing I could think of that wouldn't come out of the pot! Pulling some out of the top pond after 4 years, I saw that the soil was just as firmly in there as when I first placed it in.

Yes there are probably a lot of leaves in the bottom. My homemade skimmer made out of a utility sink didn't really work, so it has been turned off for years. I recently put a little pump in it and started it running again, but it only pulls to about 5' in front of it- and that's not a lot.

I think I'm a walking advertisement for pond stores. None of my DIY really worked. But, on the other hand, if it had been an expensive project I couldn't have done it. Just little old me over here on a city paycheck.

Thanks for pointing out that the water would stay stirred up. I did not think of that.

If just a gentle swirl settles out a large amount of debris, how would you suggest that I get this out? Opening up the valve I have on the drain does not do it - even though I have the force of the pump pulling from that drain.

Moving all of the media to get down to the bottom of a 300 gallon skippy is quite a job. I didn't want to put the media in mesh bags this time since you guys mentioned that the water will short circuit around the bags instead of going through them.

Carrie

Sandy and Carrie, et al, I think that this thread should be read in conjunction with Carrie's related post, "Washable AC Filters" to appreciate the whole picture of what is going on with Carrie's pond and present filtering system.

Sandy I believe you are on the right track, that the dirt is being constantly stirred up as things are now. A major clean out of the pond bottom and a possible revamp of the bottom drain inlets has to be addressed, or the problem will keep never be rectified.

Carrie if I lived closer to you, I would gladly volunteer to assist you with the clean out and the revamp of that bottom drain, but alas that's not the case.
"Horton"