Best way to purge sediment from tanks??

[Yellowbird]

My club purchased a 1967 PA140/160 at the end of the summer. The airplane appears in very good condition and runs great, but it has not flown much in the last couple years. We are having a sediment issue, principally the left tank, but also the right. We also get a little from the gascolator, but far less. We took the gascolator apart, and the screen was clean-- what sediment gets to it sinks to the bottom and goes out with the sumping operation. If you don't take a big sample, the wing sumping valves often leak, consistent with debris on their seats.

The samples run clean after about 1/3 full in the Gats jar, but then there is more sediment after the next flight. I am wondering if this is safe to fly, or do we need to clean out the tanks? IF cleaning the tanks, which I am inclined to do, is there a way to get a hose through the filler and baffles to the low point to suck directly from there? If not, I am thinking perhaps we could drain the tanks, first part way by siphon, then remove the drain valves. Follow with a few fuel purge/flushes until the sediment clears. OR --- is it necessary to remove the tanks? Also curious what this stuff is, if anybody knows??

This Photo is from the left tank, a day after last flight. Thanks for inputs!

 

[piperowner]

 

[Tweety]

 

[Domenick]

 

[Yellowbird]

 

[jruhnke]

 

[Tweety]

 

[Tweety]

 

[Ray93J]

 

[Tweety]