gsxunv04
I stole this pic from another thread (
http://reefcentral.com/forums/showthread.php?s=&threadid=1349177 ), but it is a perfect way to understand the hartford loop.
You see how the water level on the loop output will go up as high as the tee on the outside of the tank?
If you insert an adjustable pipe between the Tee ( where the air vent is ), and the bulkhead to the tank, then you can adjust the height of the water in the tank. The same concept applies to a hartford loop on a skimmer.
I use one on my skimmer and I can adjust the height easily. However, I used a compression type of adjustable pipe,
and I should have used a slip coupler ( adjustable length pipe for repairs ).
Like this one ( look at the top of the pipe coming out of the Mag12 near the elbow at the top ).:
Using the compression type requires me to completely drain my skimmer to make the adjustment.
If I had used the type in the second pic, I could adjust while it is running.
Stu