Tuesday, May 4, 2010

Surged Air Pressure Trumps Static Hydro Pressure

Over the weekend, I had to do another round of pool maintenance. The cammed 6-channel pool cleaner had developed a notch on the ramp-up side, so some of the cams were sticking as they tried to ramp up, making the planetary gear train stick in place, and "jump" the water driven sun gear. So I depressurized the system, took off my new $165 cover, and smoothed out the plastic injected nylon cam with a box cutter knife, carefully, gradually, so that it was "smooth to the touch".

Reinstalled, I cranked open the pressure relief valve again, and started up the pump. Huge amounts of air surged through the pipes, and jetted out into the pool - as air does each time the system is depressurized... but this time, was different. On the top step of the pool (conveniently) a large fountain had formed. I ran over to see the pop-up head (on the left in the photo) laying on the bottom of the pool, and it's black o-ring, about 10 feet away. The top step is the FARTHEST away from the pump, and the highest elevation of the 6 cleaning channels, so it gets the most air when depressurized.

If you look closely in the picture, you can see the white tabs on the left head, and the absence of white edges around the tabs on the head in the middle of the photo. The white tabs are cracks in the polyethylene plastic injection molded part. Those tabs interlocked with mating channels in the sleeve inserted in the pool's top step. The surge in air pressure impact loaded the pop-up head, and hammered it repeatedly, until the tabs cracked (there's 4 circumferential tabs, equally spaced) and the head popped out, leaving it's o-ring behind, which then flowed out with additional water later.

So I cut off the pump, and rummage around in the garage in the small box of spare pool parts the previous owner left us. I found the white box from A&A Manufacturing "The Makers of Unique Automated Pool Products", 1711 West Culver Street #10, Phoenix AZ 85007 and the white delrin tool with 3 prongs. Comparing spare head to broken head, it became immediately obvious what had gone wrong. Having no shortage of testosterone, I think to myself "tool? who needs a tool? I can insert & twist this back in place!" Duh, no, I couldn't. I tried to insert and 1/4 twist the new pop-up head into place on the top step, 3 times, unsuccessfully, having it pop off as soon as I turned the pump on and pressurized the system. Back into the garage to fetch the tool, which until this moment, had seemed superfluous. Mating the 3 prongs with the 3 notches in the face of the pop-up head, it inserted easily, and has been running without issue for 2 days now.

The additional wing nuts and "U-joint" on the insert tool, would be helpful if it was the middle of the winter and the water temperature was below 60F, and a head popped out in the bottom of the pool, instead of the conveniently accessible top step.

So many thanks to my home's previous owners for leaving me such useful replacement parts and handy insertion tool! I'll be sure to leave these for the next owner as well. =)

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