Are you turning stop valves half closed to slow water, while filter is still running?
If so thats the reason.
Leave them on full open when filter is turned on.
I know alot of people say its ok to leave them half closed while filter is on to slow the flow rate. But, If you leave them half closed, while filter is on, the water puts too much pressure on the valves and leaks.
If you want to slow down flow, drill bigger holes in the output end pipe spray bar, or even take out the spray bar.
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