My wife told me she wanted to move the small (20 gallon) fish tank out of the activity room and into my office so, of course, like any logical person would, I thought "Score! I get to build another AP system!", because what would a fish tank be doing in my office if not to grow plants?
Step 1: Prepping the Bed and the Siphon
I used a large mortar mixing tray (about $13 at Lowe's or Home Depot in the mortar/cement area) for my grow bed. It is a little smaller than what I would normally use as I prefer to be about 12" deep. Unfortunately, since I am growing on a shelf and am limited on both height and weight (shelf capacity is about 350 pounds and rocks and water get heavy), I went with the tray that is only 8" deep.
You will notice in the picture of the piece that goes through the tray is not a bulkhead fitting. ¾" bulkhead fittings are about $13. An electrical watertight box fitting is about $2 and works just as good on small loads like this.
Drill the opening through your tray at 11/16ths and thread it in with the rubber bit on the water side and the metal bit on the bottom. Use a wrench to tighten snug but don't think you have to make the metal one with the plastic.
This is an area that many people have problems with and it really is not that difficult. In the picture, you will notice that I have a 3/4 pipe coming out of the throughpipe, then I am using a 1" to 3/4" reducer (well, a reducer would be nicer, I had to use a 1" coupling and a !"-3/4" bushing because Lowe's did not have any reducers. Anyways - The top of your small pipe at the top of the reducer is going to be about 1/8th of an inch under the max water level. You typically want your max water level to be about 1-1½ inches below the top of your rock, so plan accordingly.
The outside pipe needs to be slightly larger than the largest part of your siphon. Since I am using a 1" reducer at top, I could have went with 1½" pipe for my bell, but went with the 2" because I had some laying around in my shed. Cut your bell pipe so that it will be roughly a half inch (½") taller than the top of your reducer. Now put a cap on it. The cap will add another quarter inch to the height. You do not need a plastic break line!
Instead of using plastic break lines, which tend to tear down over time, I simply drill holes in the bottom of the bell pipe. IMPORTANT! The highest hole will be the amount of water that is always left in your system. Typically in a small system like this, you do not want to get over 1" of bottom water so drill as many holes as you want in your bell, at the bottom, under the 1" mark. When your siphon is running, it will break as soon as the water level gets down to the top hole.
Now, get you a 3-4" pipe and drill a bunch of holes in it and put it on the outside of your bell. This is not a requirement but if you ever have a problem with your bell, you will be glad you have that bigger pipe to get easy access to it.
Step 2: Finishing Touches
IMPORTANT!! Don't forget to make time for the kiddos. Had to take 30 minutes out in the middle of the build to play Candy Land with my little girl before bed time.
Photos: Look at photos and hover over notes for more insight.