I am in the middle of a SLAM. The PSI gauge on my Hayward sand filter has been slowly creeping up over the last few weeks, and even after a backwash does not go down. And it doesnt go down when the pump is off either, so I figure its either broken or malfunctioning. However, I went out yesterday to brush the pool and add bleach, and saw that the PSI was 8. It had been around 22 earlier in the day. Since the gauge is suspect, Im not sure whats really going on. However, I went and checked the flow at the return jets into the pool and they are definitely flowing stronger than normal.
So now Im wondering if somehow the filter is somehow being bypassed since the pressure is so low. Is this possible? The selector is in the normal 'Filter' position. Can a Hayward sand filter malfunction in this way?
One more piece of info, I added about a cup of DE mixed with water to the skimmer the day before this to help clean up the water during the SLAM.
I ordered a new glycerine filled PSI gauge from tf, but dont have it yet.
Thanks for any help!