If sand starts to flow out into the pool then you must remove the sand, take out item #11 and then the sand and finally item #13 and replace the items #15.
The pool was a disaster. Although it was clean there was very little suction at the intakes and hardly any pressure at the return sites. To get the automatic sweeper to work I had to turn off the returns from the bottom of the pool and the skimmer. I kept asking Pinch-A-Penny why the pressure gauge on the sand filter read 0 and their response was that the gauge was bad. The gauge was brand new. When I would remove the gauge air would be sucked into the sand filter. At last I asked Jay what to do. His friend from West Marine was with him as we looked at the system. Their observation was that the impeller was making a grinding noise and it took far too long for the pump to draw the air out of the strainer bowl.
At their insistance I finally removed the impeller housing and found the impellers clogged with concrete. The concrete had come from the pool deck when the tiles were removed. This helped answer the problem that had puzzled me for three days. The pressure gauge on the sand filter kept reading "0" and no one could tell me why until I asked Jay and his sailing friend from West Marine. They analyzed the problem after listening to the pump run for two minutes. They noted that it took far too long for the pump to prime itself and the pressure of the return water was insignificant. So the answer to why the vacuum gauge kept reading 0 was that the impellers were clogged and the suction created by the pump was barely enough to run the automatic pool cleaner. It is amazing that there was enough suction to operate the automatic cleaner, even if it were on a dedicated line. Tomorrow I will get a new "O" ring for the impeller cover and three move screws to hold the impeller cover in place.
THE PROBLEM EXPLAINED.
8:20 am June 13, 2011.
When the pool circulating pump is not running there is a negative pressure at the sand filter gauge because it is 6 feet above the pool. Since water pressure is 0.5 lbs per foot of height the vacuum at the gauge should be -3 ft. lbs. When the pump is turned on the pressure should increase to 14 or 15 pounds positive. Once the pressure rises to 22 pounds it is time to back wash the filter. Because the impeller veins were clogged up the pump was barely moving any water through the system and the pressure never got up to 0. It will be interesting to see what happens today when I get a new "O" ring for the impeller housing and reinstall the pump.
12 noon, June 13, 2011:
The new "O" ring was installed and the fittings were tightened down. Once the air lock had been resolved and water began flowing through the system the pressure went to 15 pounds. The bleeder valve was opened and air was allowed to escape. The motor is much quieter since it is not grinding away on the cement. Water comes out the pool jets with much more force, a situation that has not been seen at the pool for 4 years in sprite of several service calls and repair bills from various pool companies.
Notice that the valve handle is in the 5 o'clock position. In the 6 o'clcok both the skimmer and the bottom drain would be shut off resulting in a pressure reading of 15 lbs. and the vacuum on the hose line would max out the gauge. By opening the valve completely the pressure goes to 20 lbs and the cleaner would not have enough vacuum to function.
For information on the Triton II fiberglass sand Filter.