DIY PVC SIphon

Transferring water from one tank to another without a pipe below the waterline is sometimes called for. You could use a pump and hose, but if this is part of a filter system, you might not want the pump at the head of the sequence. The impeller can turn suspended particles that could be removed easily into super-fine particles that are very difficult to remove.

And just maybe you *really* don't want to make a hole in the tanks and install a bulkhead fitting. Some people seem to have a phobia about that.

So, here is how I move water through a pipe, without a pump attached to either end! A "Do It Yourself" two inch PVC Siphon.

This is very "do-able" when you want to move water from tank to tank, with the water levels in both tanks the same. With the siphon in place, when you pump water out of one tank, it's water level drops. Water will seek it's own level, so water from the other tank moves through the siphon, into the tank you are pumping from.

If one tank is the pond (Tank A) and the other is a mat box or settlement chamber (Tank B,) you can pump from Tank B into a filter that returns water to the pond. As the water level in Tank B begins to drop, water flows from Tank A through the siphon.

Some tips on putting the siphon together and into use:

The end of the siphon that goes into Tank A needs some way of keeping fish from passing through it. Ideally, that would be a plastic screening with a mesh size smaller than your smallest fish. With fry, put a wrap of ¼ in mesh around the end with the holes in it first. Then a wrap of 1/8 inch mesh on top of that, and window screen on top of that. Finish it off with a final layer of dense filter mat. This way, after the fry are about a week or so old, you should be able to remove the filter mat wrap. This will keep you from having to pull the siphon and clean the intake filter so often. As the fish grow, continue to remove the outer wraps until you get to the ¼ inch mesh. When the fish are large enough, the plastic mesh can go, too. The idea is to let any and all solids pass through the siphon and into the solids removal tank (Tank B,) while keeping the fish in Tank A.

The end of the siphon that goes into the pond, Tank A, should reach all the way down to the bottom. The bottom of the siphon should have either an end cap or the same kind of intake screen that covers the holes. I drilled large holes in the last foot of the intake end. Depending upon the depth of the pond and how high you'll have to lift the siphon to put it in use, you might want to drill those intake holes in the last six inches of the pipe.

Figure the minimum low water level for the pond (Tank A) Transfer that level to Tank B. Make the Tank B end of the siphon reach down to that level. When the water in Tank B drops below the end of the siphon, air will enter the pipe and the siphon will stop. This can prevent an accidental pump out of the pond, should the output of the pump that takes water from Tank B to the filter comes off, or the filter return gets blocked or misdirected. You still have a bit of safety margin, even if both ends of the siphon are at the same level. When the water in the pond (Tank A) drops down to the first intake hole in the pipe, air will enter the siphon, stopping the flow.

When you think you have the dimensions of the siphon figured out, dry-fit it together. Try submersing the siphon in Tank A, cap the end with your hand and see if you can lift the capped end up and over into Tank B, *without* letting the any of the holes in the intake end above the water level in Tank A. If it can't be done, then shorten the Tank B side, or re-make the Tank A side, this time keeping the intake holes closer to the bottom.

One last note, when gluing the parts together, put a coating of PVC cement on the end of the pipe, then some on the inside of the fitting, then put another coat of cement on the pipe. When you push the pipe into the fitting and seat it, you want to see a bead of excess PVC cement push out of the joint. This way, you'll be certain to have an air-tight joint. Even a *pinhole* air leak will eventually cause the siphon to fail.

Lets do this with a full Tank A and an empty Tank B. To start the siphon, put it in Tank A, keeping the end that goes into Tank B above the water level. Lower the other end so the siphon fills with water. As the water fills the pipe, make certain that all the air is pushed out. As you submerge the Tank B end, let the water push out the last of the air and clamp down with your hand to keep air from entering as you lift the Tank B end up and over into Tank B. You may hear a small amount of air slip past your hand. If it is just a little, don't worry about it. When the end of the pipe you have capped with your hand is in Tank B, and is lower than the water level in Tank A, remove your hand. The water should rush through the pipe, driving any air that got in, right out with the water. If too much air got in, the water will not flow and you have to try again. A little practice and it gets very easy.

Anytime you need to restart the siphon, it is always easier if the level in Tank B is at least a few inches lower than Tank A. This will also make sure that any air that leaked in while you were starting the siphon is flushed out. If Tank B is too full to do that, simply pump some of the water out.

On to the PVC Siphon pictures!

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