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Continuous Water Change in the Pond


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Recommendations for pond water changes are usually 10-20% a week, although a few go as high as 30%. This is a lot of water in koi ponds that are typically measured in tens of thousands of gallons. You run a hose for a long time to add hundreds of gallons of fresh water. Many pond keepers have at some time become involved in something else while the hose was running and forgot to turn it off, sometimes losing an entire pond of fish to chlorine. Even without such a horrible mistake, filling a pond can be risky since koi are drawn to running water and often gulp the incoming water, chlorine and all. This is one of several reasons why to many ponders, water changes are feared.

Many people have gone to a "trickle in-trickle out" water change system, in which a hose is left running at just a little trickle all the time. The amount of water entering is small enough that chlorine is diluted, and all large ponds have an overflow in the system somewhere where the water can trickle out. This produces a "steady state" situation in which the water chemistry remains constant, just as it would in a lake.

If one tries to do this in a typical goldfish pond, with volumes in the hundreds of gallons, one finds that you can't turn a faucet low enough to produce the tiny trickle you need without the flow just stopping after a while. (I tried. So have others.) While most liner ponds have a low spot somewhere for overflow, a container pond just has water spilling over the top.

The solution is to put the fresh water into a large container equipped to drip water into the pond and to create an overflow pipe in the wall of the container or through the liner of the pond to let out the excess water. I first did this in my front pond and described it here. My reservoir was the thirty gallon tank of my old water softener. I had not yet discovered uniseals, so putting the hose bibb (faucet) into the side was a difficult and expensive procedure, involving a lot of sealant. It leaked on the first try, but I succeeded on the second. Then I filled the reservoir with water and turned on the faucet to a fast drip/slow trickle. It worked beautifully for a couple of hours, then stopped. The water was flowing through such a tiny crack that even tiny bits of debris can clog it, and there is always debris outdoors. I have some drip irrigation for my garden so I went to the drip irrigation section at Home Depot to see what might work. I found an adapter to connect a garden hose/hose bibb to 1/4 inch irrigation tubing. Then I found an adjustable dripper that fit into the 1/4 inch tubing. It has a screw-on end that can be tightened to cut off the flow completely, or loosened to a slow drip, fast drip, or even a continuous flow. Perfect! (Links to these products can be found in the link above.)

To go through a liner, you need a bulkhead, which is something that is not easy to find in stores. Pond stores have them, but the one here charges 3 times what I paid on line. The bulkhead sandwiches the liner between two gaskets and has threads on each side to attach pipe.

Most overflow pipes simply skim water off the top of the pond. I run the pipe to the bottom of the pond to overflow the dirtiest water. When it rains, the rain falls on the top of the pond the pipe picks up the old water at the bottom of the pond and overflows that. As a result, every rainfall gives me a free water change. Don't use this system if you have soft water and acid rain, since that could cause a pH crash. Just let the pipe collect water from the top.

I adapted this system to a 50 gallon stock tank pond as described in post #10 here. This was much easier, since I used uniseals to go through the wall of the reservoir bucket for the dripper, and through the wall of the stock tank for the overflow pipe. Each are ten minute jobs. It took two days to put the faucet in the reservoir for the front pond, since I had to let the sealant cure. No sealant with uniseals.

Overflows from container ponds are all very much alike. However I have tried several designs for dripping water from reservoirs into the pond. I will describe and picture these in the next post.

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I'll give the "redneck" version of a dripper from a clean water reservoir. It's cheap and goes together in no time. Basically, it's a siphon of 1/4 inch tubing with an adjustable dripper on the end. One does have to stabilize this, and I do so with some pvc pipe.

I wanted to use this 30 gallon drum as a temporary fresh water reservoir for the back pond.


It's ugly, so I intended to replace it with something that looked good. Since I would probably find another use for the barrel, I didn't want to drill a hole, so I decided to go the siphon route. I cut a piece of 1/2 inch pvc long enough to reach to the bottom of the barrel.


I made this structure by putting an elbow on each end and threading 1/4 inch tubing through the pipe.


I put it in the barrel to determine where to cut the tubing for the dripper, cut it, and put on an adjustable dripper.


I filled the barrel with clean water and started the siphon. The "soda straw" method is the about the only way to get the tube filled with water. No problem, it's clean water in a clean barrel. By keeping the base of the barrel an inch or two below the pond water level, one can assure that the barrel doesn't empty so the siphon stays full of water.

I also have a 5 gallon bucket that uses the same system. That's open, so If the bucket empties, I remove the dripper cap and refill the tube by putting the hose over the end of the tube inside the bucket and blasting the water through.

The advantage of this system is it's very cheap and easy to put together. The main disadvantage is that the long thin tube clogs more readily than the other types. The tubing is very cheap and replacing it is not much of a job. Because the tube comes out the top of the container, a cover doesn't fit on well. I like a cover to keep out debris and an occasional clumsy little anole lizard. The lizards can sit on top of the water for a day or more, so I can rescue them. And, of course, it looks rather redneck.

My original water reservoirs used hose bibs with drippers attached like the one shown here in post #10.


These are very good drippers, but the hose bib costs more than the materials in the other types.


Edited by shakaho
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The next dripper assembly started when I found this in irrigation in Lowes.


This has a 1/2 inch female thread at the bottom and a 1/2 male thread at the top. The side arm is a fitting for 1/4 inch tubing.

Also in the irrigation department, we have risers.


This is a piece of 1/2 inch pvc pipe with male threads on each end. This can go through the side of a bucket through a uniseal. The outside end can screw onto the the female end of the "manifold" above. Then I can put a cap on the male end of the mainfold.


Then any water in the bucket will go out the side arm, to which I will attach a couple inches of 1/4 inch tubing with an adjustable dripper at the end.

Here are some pictures of the assembly. When I initially made this, I had a manifold with four outlets similar to this one, and that is what I have in the pictures. When I found the one with one outlet, I replaced the original.


Here you see the 1/4 inch tubing at the top. At the far left is the adjustable dripper. The eight objects to the right of it -- some plugs for three of the four outlets, four connectors, and the four outlet manifold were eventually replaced with




Then we have the riser and the bucket.

Here is the 1/2 inch uniseal and the bucket marked for the hole.


I put a hole saw on my drill and cut the hole for the uniseal


I took some sandpaper and made the hole nice and smooth to fit in the uniseal. The piece of bucket cut out by the hole saw goes into my box of plastic-scraps-that-can-be used-as-filter-media. :)

Uniseal in the hole.


Riser in the uniseal.


Now I just have to scew the manifold onto the riser. Some teflon tape makes the seal tight.


Then I screwed on the manifold.


I put on one dripper and three plugs so it originally came out like this:


It worked. I still replaced the manifold with the single outlet one, so it now looks like this:



I reused the four outlet one for a large reservoir that dripped into three different tanks. That worked too.

The "irrigation system" is great. It works as well as the faucet system, but is a lot cheaper.

Riser $0.37

One-outlet manifold $1.59

1/2 inch pvc cap $0.77

Adjustable dripper $0.49

1/2 inch Uniseal $2.00

$5 and change. A cheap hose bibb alone is about $5.

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Most of my reservoirs are pretty small, since they drip into a stock tank. For my back pond, I wanted something big that wasn't quite as conspicuous as a plastic drum. I had a rain barrel that I didn't like where I was using it, that looked like a perfect fit for the corner of the pond. It holds 55 gallons of water.


The nice thing about a rain barrel is that it comes with an outlet for attaching a hose for using the water collected. I cut off most of the hose, leaving enough to reach over the edge of the pond.


I wanted to drip water from the reservoir, so I got one of these which connect the male end of the hose to 1/4 inch irrigation tubing. I put an adjustable dripper on the end and screwed it on the hose. I slid the black pipe and elbow over the hose to make sure it stayed where I wanted it.


The top of the rain barrel:


The square in the center of the lid comes out. There is screen under it to keep out mosquitoes. Note that in the lower right of the lid there is a hose holder. This means that when I fill the barrel I can clip the hose there, bend the end down into the barrel, and let the water run while I do something else.

Here's the reservoir in use. It doesn't look bad, but one can get much nicer looking rain barrels if one is willing to spend the money.


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Wow! Those were great posts :thud

Do you want to come to St. Louis to build a pond for me? :D

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So far, I've talked about the fresh water reservoirs.  The other part of continuous water change is overflow.  With a stock tank pond, this is very easy. You can see it in post # 10 here.  




You drill a hole in the tank where you want the outlet (usually as close to the top as possible, put a uniseal in the hole, and put a pipe through the uniseal.  You now have an overflow pipe.  If you want it to drip neatly into a container, you just put an elbow on the outer end of the pipe and put the container underneath.  


However, I want to maximize the water change, so I rather than skimming the surface of the water, I want to discard the dirty water at the bottom of the pond.  So I put another elbow on the inside end of the outflow pipe  and add a pipe that goes almost to the bottom of the tank.  When the water level reaches the overflow pipe, water begins dripping out, and that water comes from the bottom of the pond.


The only difference between a large and small tank is the length of the pipe that goes to the bottom of the tank.  Inside a 100 gallon tank:









Looking at the whole system in the picture below, you see the overflow pipe coming out at the left.  The pump is right next to the outflow pipe inside the tank.  At the right side of the tank, you see the filter, and to the right of it, the reservoir.  The tubing from the reservoir outlet is long enough to hang into the tank.





In every system, I have a "clean water in" end where the filter and the fresh water reservoir empty into the tank and, at the opposite end,  a "dirty water out" with the overfow and the pump.  This creates a gentle flow of water through the tank.  If I watch carefully, I can see bits of debris slowly drifting from the clean end to the dirty one.  When I go to vacuum the tank, there is always a little pile of solid waste right near the pump, which makes for easy cleaning.


The next outflow pipe is interesting because I needed to guide where the water went after it left the tank, but I didn't want to create a siphon that could empty the pond after a heavy rainfall filled the outflow pipe.  So I just drilled some holes in the top of the outlet pipe to break the siphon.




Edit:  This one is funny because all I had to do to "break the siphon" was to replace the elbow inside the tank with a t-fitting with an open top, just as I  do on the top of a filter.

Edited by shakaho
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