I use the aluminum flashing .
L shape up the wall and out onto the joist.
Deck over it letting it extend out the same width as the deckboard, or jus a tad less ,so it wont catch water.
I only do the first 5.25" so water doesn't channel in between.
If you want you can double the flashing. It will...
If there is no signs of water you may not have a leak.
It might be pipe creep. Pressure in the pipes build & release during use. Plunmbers secure pipes with straps ,clamps, ties ,etc.
I had a customer a decade or so ago insisting she had a leak. I said wheres the proof ? The water puddle ? The...