page 50 (I THINK)
On my migratory waterfowl thread ( in the sticky section for ducks)
has some of my old ones
If built with a drain, yes they are easy, pull the plug and wash down with bleach and a hose.
if not, they are a nightmare, You will have to get a sump pumg and drain them, them shovel all the mess out by hand.
I would highly advise a drain system.
Filters not needed, it would take a super massive one to keep up with a lot of ducks any way.
no real right way to do it
just dig your hole and pack it with at least 3 inches of cement.
The drain should be at least 3 inches, I used 4, to keep from clogging
I stubbed up another section of pipe to the water level. at the water level put a cap on it, but drill some holes at the water level line of the pipe. This will allow drainage in storms or what not to prevent flooding the pen.
Do not glue this section in, leave it press fitted.
Now when you are ready to drain, just grab it and pull it out and you are good to go.