Pentair FNS Hi-Flow backwash valve leaking to waste

[naztuk]

I have a Pentair FNS filter with a Hi-flow backwash valve. The top was cracked at the bolt holes and leaking so I replaced the top along with the diverter gasket. I have adhesived the gasket in place as recommended and checked and re-checked the correct alignment of the valve top, but still when I turn the system on in the filter position, it leaks water out to the waste discharge outlet. I am stumped as to why this is happening. Can anyone provide help to fix this issue? Thanks

 

[Bama Rambler]

Welcome to TFP.
Remove the top hat again and closely inspect the gasket as well as the partitions. If there are no cracks or nicks then lube it with silicon pool lube and carefully put it back together.

 

[naztuk]

I have checked for cracks and couldn't visually see any. Does the diverter gasket need to be installed a certain way. 1 side has a square sealing area while the other side has just a thin line of rubber as the sealing area.

Also when you say silicone lube are you referring to a lube like Aladdin's Magic Lube?

 

[Bama Rambler]

Any 100% silicon lube will do. Look for deep gouges along the sealing surface too. Your spring may be weak allowing the water pressure to overcome it.

 

[no-mas]

Could you have installed it backwards? What happens if you set it to backwash?

 

[naztuk]

The top is new so I don't think that the spring would be at fault. The diverter gasket has one side the has a square lip in the middle that matches the channel on the valve bottom. The other side of the gasket is a thinner lip. I've tried both ways without any luck. I'm starting to think there is a hairline crack in the bottom housing that I can't see. It may open up as the pressure inside builds and then leaks out to waste.
When I move the handle to different positions on the valve it still leaks out to waste.