I was thinking 'how to do it' as well HHF. To get the water out you just need to shut your feed valve, turn on a tap or hose until it pumps down as far as it can. Then, hose and brush down the sides from above. I think there's a reservoir at the bottom below the out line that catches any sediment so it's not pumped into your system.
You could then use a pump truck that does the septic tanks but I don't know if they have a sanitary hose to use for that? No way I would want them to stick one of their poop hoses down there.
Another choice as Terry mentioned is to get a small guy down in there with a bucket, a scoop and some rags.
Yet another would be a shop-vac or similar.
Let us know if you do it and how. Pete
