Backwash Valve Problems, Higher Pressures, De Filter Lid Lifting Up

[smokey]

I've been maintaining our spa for 11 years since it was built and ran into a new set of problems. All of these things were discovered at the same time, but I don't know if they are related.

1. The backwash valve (pictured below) when moved to the backwash position feels good and appears to operate correctly, but I'm guessing maybe 10% of the contaminated filter water is deposited back into the clean spa.

2. The filter pressures are/were higher. Normal pressure for the filter pump is 26 psi, increasing to 34 psi when the booster pump is used. That increased to 34/40 psi last night until I backwashed. I've never seen pressures go that high. After the backwash, the filter pump returned to about 26 psi at first, then crept up to 28-29 psi. Usually, after a backwash it returns to 26 psi and holds there. The spa has not been used much since I disassembled the filter and did a full cleaning, so none of these behaviors would be considered normal.

3. While standing at the service panel, I noticed the lid on the DE filter raises up against the clamp when the filter pump is activated. Not much, we're talking 1/16" to 1/8". I've stood at the service panel hundreds of times previously and this has never happened until last night. Makes me a little concerned the pressure gauge could be defective (on the low side) in addition to all the other problems. The gauge was showing 28 psi when I noticed the lid movement.

Any ideas? I plan to disassemble the filter with the pressure safely exhausted tomorrow.

[Pool Clown]

With the pump off and, if the equipment is below water level, close the valves. The top of the backwash valve will unscrew and allow you to remove the slide. Confirm that the disks on the slide are 1) still there, two disks. and 2) in the right position (have not slid up or down on the shaft) this would cause the ports to not seal completely, and allow dirty water back to the pool and possibly give you the high pressure you are experiencing. post a pic of the slide once you get it out.