I am building a pond with the following shape, measuring about 40 ft across. The wall is there to keep out mud from flash floods. It is made of brick, but has a reinforced metal frame to hold the actual liner, so there's a small working space between the liner and brick wall to run pond lights and future upgrades. The pond water doesn't actually press against the brick, there is a 2" hidden gap. The center 6 ft. The outer ring is almost 2 ft deep, so providing safety for children and stability to the ground under the wall.
I will install a 4" pipe like so (see yellow pipe), with the top a water level, in case heavy rainstorms dump too much water in the pond. This causes the water to be redirected to a safe place, instead of spilling over the sides and flooding the yard, as we do get monsoons that can dump massive amounts of water. The 4" pipe size might not even be sufficient give the rate of rainfall here...
For filtration, I plan to carve out an area that is somewhat within reach in the shallow area just over the wall. The liner will lay in this area, filter equipment above it, then buried under river rock, so as to hide it completely. In the picture above, it is the rectangular cut-out area.
The pump is of homemade design. The red pipe represents where water goes in, thought that might be just a grill hidden under river rocks. The water passes through three large trash cans, exits through a pipe, that possible will snake all around the pool and exit near the rim, to push the whole of the water in a large circle. I wasn't able to illustrate the flexible pipe, but you can see the exit of the pipe in the left of the drawing, just under the water. It points in a manner that would cause the water to circulate counter-clockwise, at least in theory. This worked on tests in a round 3,000 gallon swimming pool, but because this size is larger, I don't know if there will still be good circulation.
For a close up of the homemade filter design see above.
a. Water enters the first submerged trash can. I think the top could be a vent covered in river rocks, but I don't know if that will disrupt the flow too much.
b. The first trash can contains pumice.
c. The second trash can can contain filter floss.
d. The third trash can holds the 4000 gph pump.
e. PVC connects the three trash cans.
The whole design is buried under river rock.
Do you think this design can work?
Any suggestions for improvements? Any suggestions for how to make the filter more easily accessible?