Kreepy Krauly is a brand name of an automatic pool vacuum. You hook up the device by a hose to the pool’s filtration system, and water drawn through the KK head makes a piece on a pivot inside flap back and forth, steering water being drawn through the device alternately through one of two paths to the hose. Somehow, this makes the KK head move along, in a more or less random pattern, so that eventually the KK has vacuumed the entire pool. The device will even crawl up the sides of the pool to the water line.
Soooo … please, can anyone explain how this thing works? Why doesn’t the KK head just sit there, vibrating?
Well, I got this straight from the FAQ on the Website you posted:
>>The way that Kreepy Krauly works is the key to its reliable, trouble-free operation. With just one operational moving part, it converts the water flow generated by your pool’s pump into kinetic energy. Here’s how: the water flow first moves the flapper (the only operational moving part) to the top position, causing one drive tube to close. Water is drawn in through the open drive tube, which causes the flapper to move to the bottom position. This repetitive process creates the motion which propels the cleaner around the pool. <<
To elaborate on Dooku’s answer, it’s basically just the jerking motion of the flapper that yanks the unit forward. Since the flapper is offset from the unit’s center of gravity, it’s pulled forward. It’s a kludge solution, really.
Having gone through two Kreepy Kraulies on my parents’ pool, I can assure you that it the unit’s forward motion is pretty temperamental; it’s VERY prone to problems. If there’s too much or too little pressure in the pump it won’t work. The unit has to have a good seal or it won’t move at all, so the hose has to be balanced right (the weight of the hose can cause it to nose over) and it will get knocked off its seal if it runs into anything at all, including ladders, stairs, wash from the water jets, or the bottom filter. The flapper is very prone to jamming, so a leaf can stop up the whole works.
The unit’s pattern is also dependent upon the shape of your pool’s bottom and the weight and length of ther hose, so it takes a LOT of experimentation to find a combination of hose length and weight and water jet positioning that will cause the unit to actually cover most of the pool without getting hung up on something. You can spend weeks watching the damned thing either run in the same circle endlessly or keep getting caught on something before you get the pattern right.