How to Build a Siphon Part 2

Alright Trifecta fans.

Today we actually build a siphon. So let’s dive right in, starting with materials we are going to need.

  • 2 ft of 1 in PVC pipe,
  • Two 1 in PVC elbows,
  • Two 1 in threaded PVC males,
  • 1in bulkhead,
  • A 1 and 1/4in to 1in bushing,
  • A 1and 1/2in to 1 and 1/4in bushing,
  • 2ft of 2in PVC pipe,
  • 1 2in PVC Cap,
  • 2ft of 3in PVC pipe.

Plus your media bed.

We will also need a hand saw or preferably a sawzall/reciprocating saw, measuring tape, dril and a 1 and 3/4in circle bit.

The siphon we are building was used in a media bed that was about a foot deep a foot wide and a foot and a half long. The foot deep is the important part. It is generally recommended that you have a media bed of around a foot, we’ve gone as shallow as 8 inches and as deep as 15. Don’t go below 8 inches it really won’t leave enough room for proper flooding and draining with a siphon. This size media bed and siphon are designed for converting an existing in home aquarium to an aquaponics system. You would need to place your system by a window that gets good light or provide supplementary light in order to grow plants.

To start, determine where you want your siphon within the media bed. Then using your drill with a 1 and 3/4in circle bit drill the hole for the siphon. If you’ve never used a drill with a circle bit they can be a little jarring at first. If possible get a second pair of hand to hold the media bed secure while you drill the hole with two hands on the saw.

Install the bulkhead into the media bed where you cut the hole. The bulkhead consists of 3 parts, the main piece, the screw and a gasket. Place the gasket in the media bed around the whole, then put the main piece through the whole. Secure the bulkhead in with the screw piece on the outside of the media bed. Tighten it up as good as you can but don’t kill yourself over it. This bed is sitting over our fish tank a little drip will not hurt anything and you can overtighten also creating an imperfect seal.

Now flip the media bed over so you are working with the bottom facing up. Next Screw in one of the threaded male pieces into the bulkhead. With that complete cut 5 inches of 1in PVC pipe. Insert this cutting into the slip of the male piece you just screwed into the bulkhead.

You’ve just installed the drain of the siphon. In order to finish it we need to add one of our elbows to the one inch pipe sticking out. Then we need to cut another 5in or so piece of 1 inch pipe. Slip this cutting into that elbow. Finally add the final elbow to the just added 1in section.

The next steps and measurements are for our media bed that we used. Which we link you to in part 3. In fact we will link you to all the materials we used just so there is no confusion as to what I’m referring to. However, if you decide to use a different sized media bed you’ll have to adjust the measurements accordingly here on out to match your media bed depth/height.

So next we are going to cut our standpipe from our remaining 1 in pvc pipe. We have a 12 inch bed and we want the water to rise to about 1.5 inches below the top of the media. I’m going to assume that i won’t get the media all the way to the lip of my bed so i’m going to cut my pipe so it is draining water at the ten inch level of my bed. Because my two bushings when put together are 1.5 inches i need to cut 8.5 inches of 1 inch PVC pipe. I’m going to slip this piece into the remaining male threaded connector and then i will add my two bushings to the top of the pipe. After i will screw it into the bulkhead. This series is represented in the two images below.

Next step is to cut your 2inch pipe. Cut your 2 foot piece in half to make a 1 foot long section. On one end of this pipe cut out teeth from the bottom portion. This can be done with hand or reciprocating saw. Use your saw to cut two lines one in apart up the bottom of the pipe. Make these lines the same height anywhere between .5 to 1 inch. Then cutting horizontally saw into the pipe until the lines connect and the “tooth” should fall right out. Make three or 4 of these teeth along the bottom. Place the cap at the end of the pipe and then cover your standpipe with this piece letting it rest on the bulkhead as pictured below.

Now we are down to the last pvc pipe, our 3 inch section. Again cut our 2ft piece in half to create a 1ft section for use in the media bed. On the bottom half of one side cut into the pipe horizontally so the saw pierces into the pipe but don’t cut through it. You are making slits for water to pass through but to also block media from entering the siphon. The more slits the merrier so long as the are thin and don’t go more than halfway around th pipe. Refer to our first picture to see an example of what the slits should look like. Then place this pip around the whole siphon with the slits down first. Refer to the image below for any clarification.

Now its time to place your bed over your tank in a nice sunny spot by a window unless you have supplemental lighting. See pic below.

Add you media slowly and be sure to add it so it rises level. Don’t overload one side or the other around your siphon you want to make sure it remains rigid and straight or it may not siphon properly. Continue adding media until you reach the top of your bed or your predetermined desired height as shown in the pics below.

You are now ready to connect your hose and pump and flow water into the media bed. The water will rise to your predetermined height. In our case 10.5 inches up our 12 inch media bed. When it reaches that height it will overflow into our bushings. They reduce down from 1.5 to 1 inch. This cause pressure which initiates a flush down the 1 inch standpipe. This flush activates the siphon due to the bell portion around our standpipes. The water will continue flushing out of the bed until the water level reaches the teeth section at the bottom of the bell unit. This will break the siphon. The water will rise back up to the standpipe over time and then siphon all over again.

If you find your siphon isn’t flushing or gets stuck in limbo where it is just acting as a standpipe. Play with the elbow at the end of your drain pipe. Start with a 90 degree angle and the twist down until the siphon flushes. Leave the elbow at that position and wait for it to siphon again. If it siphon’s again leave the elbow be, that is the position it needs to be in. If it doesn’t siphon adjust as necessary until it siphons repeatedly without adjustment. Our elbow is perpendicular to the standpipe and parallel with the water, it does not need a tilt downward however we have seen that work in other systems.

If anything is unclear please leave a question in the comments or email us directly at  The goal is to make this as simple as possible so if something is unclear we want to clear it up for you. Also stay tuned as we will have a video of how to build a siphon for a larger scale media bed. The principle is the same the pvc sizes change a bit. The video will show you how to make the cuts and assemble the siphon also will show it flushing versus acting as a standpipe.

Finally stay tuned for part 3 of the How to Build a Siphon series where we will link you to every material you will need to accomplish the siphon built in this post. We will even include a link to the media bed we used. It is a small media bed to be sure but it is food safe and a great option for you if this is your first foray into aquaponics.


Thanks for reading. You can check out Part 3 here and Part 1 here.

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