Hofer Gurgle Buster Construction Page
Above are the approximately $3 worth of PVC Parts Required (air tubing not shown)
Notes: The coupler is 1.5" (female slip) x 1.5" (female slip), and the bushing
is 1" (female slip) x 1.5" (male slip). Also, some overflows may require
another 1" x 1" coupler to attach to the overflow's standing pipe.
STEP 1 : Sand 1" inside of the 1.5" (male) x1" (female) slip bushing such that it can
slide over the 1"-in-diameter pipe with considerable resistance.
A dremel is recommended (but not required) for this step.
STEP 2: Press the coupler and bushing together to form bell (aka flow bell).
STEP 3: Drill 1/4" hole in top-center of 1" end cap and push the air tubing through.
The air tubing should slide with considerable resistance through the hole.
Drill 5, 1/2" holes or any assortment of large holes in 1" pipe.
Holes need to be roughly positioned as shown below.
STEP 4: In picture above, take end cap and push it on 1" pipe on the side that is about 2"
from top of holes). The end of the air tubing should rest a little bit below the drilled holes.
STEP 5: Push together all parts seen in step 3 (and in that orientation) together.
The Hofer Gurgle Buster (HGB) requires two initial one-time adjustments:
ADJUSTMENT 1: BACK PRESSURE
Left (first) picture shows unit fully open. Right (second) picture shows unit fully closed.
First note that water should flow in the bell from top down (i.e. the direction of gravity). If you have the bell reversed, switch it. I have tried both orientations and flow from top going down works a lot better in all cases. In the two pictures above, the leftmost (first) picture shows the flow bell in a position that opens the holes fully. In the right picture the flow is completely blocked. Before the pump is turned on, I start with the flow bell in the up position because it is easier to push down on the bell in the tight confines of the Lifereef Slimline overflow (shown in the picture), but you can start at either extreme, open or closed. Now with the pump on and water flowing, adjust the height of the bell so the unit can handle the flow rate comfortably but not so open as to induce noisy vortices into the bell. In general you are trying to find the bell height at which the flow is maximized but noise is minimized.
ADJUSTMENT 2: AIR INJECTION HEIGHT
The water flowing past the end of the air tubing will draw air into the turbulent water flow inside the core pipe. This air is very important in order to prevent a strong siphon from forming which would otherwise induce vortices into the bell. Normally, air should be drawn below the water inlet holes as shown in step 4 above. If the back pressure adjustment was done properly, one should be running fairly quietly already, but for total silence, the air tube end may need to be slightly tweaked (usually by pushing the air tubing in further). Very slightly slide the air tubing up and down to hit the "sweet spot," the height at which all sound should stop or be minimized. Now cut the top end of the air tubing to the maximal height you would ever allow the water in your overflow. If for any reason the main holes are partially obstructed (say a large piece of bubble algae gets stuck in there), the water in the overflow will rise to the top of the air tubing, block the air flow into the tubing, and thus induce a strong siphon through the entire unit. This strong siphon action can be thought of as a backup measure just in case the holes are obstructed. The strong siphon will be noisy and will indicate there is an obstruction that needs to be cleaned out.
Well, that's it! My alias is ReefDream on www.reefcentral.com, so feel free to send me a private message with any specific questions!