| If you are still working on fixing this installation, it sounds to me that the key missing element is to install a large enough settlement or vortex chamber to handle the flow rate you will pump through the filter system.
Your current planned configuration has the Skimmer and bottom drains tied together. If you can instead rework things to gravity feed directly from the bottom drain to a properly sized settlement/vortex then you will be able to use a similar filtration system to the one we have installed on our 5500 gallon pond.
In the diagram below foul "dirty" water from the bottom drain flow up through the 4" drain line and 4" isolation valve and into the green sedimentation/vortex chamber at a low point just above the bottom cone. In this case our space was severely limitted so we had to use a 170 gallon converted commercial dumpster shell that was virtually round at the bottom and transitioned to square with rounded corners at the top. The bottom was fitted internally with a coned bottom to a 2" drain that opened 4.5" feet deep into the ground into a sump where we could salvage the sludges and used it back into the gardens and flower beds.
Water rises up in a swirling motion in the sediment chamber and passes through a solid fitted cap mat of black Matala before going into one of the two balanced 3" outflow pipes that lead into the pairs of barrel filters. You can see the 3" outlow pipes in the diagram as that penetrate out of the sediment chamber and down into the barrels. Flow into the first barrel filter in this case was by gravity into the bottom section and then across and down through the second barrel. The firts barrel in each pair is upflow while the second is downflow to the 2" suction inlets to the sequence pumps that get balanced by a two way T-valve. I used two parallel sets of barrels to get the flow rate down even lower over the bio media and also to make it possible to clean one side of the flow while leaving the biofiltration 100% intact on the other side. All of the water flow with the pumps turned onto high rate can be directed through one set of the barrels to real blast loose and accumulated film and crud.
This install works great at a flow rate of about 5500 gallons per hour but if I had it to do over again and if I had lots of space I would have used a larger and more efficient sediment/vortex chamber. In this install, we still get some sludge accummulation in the bottom cones of the first pair of barrels and this has to be drawn off be just opening the drain valves and pulling off 5 gallons of water every two to three weeks. We draw off 5 to 15 gallons of sludge from the first sediment cone every 1 to 3 weeks depeneding how much food we are feeding to the fish or combined with the airborne leaf and debris load to the pond.
If you size you first stage of sedimentation and vortex chamber to be large enough and fed properly by gravity then you could place the sequence pump after that stage and lift the water up into you DIY barrel filtration system which is locate behind some sort of visual screen. The advantage here would be that the barrels would be easier to clean and aerate and you could gravity flow back into your pond through a water fall system.
Our system uses gravity flow for everything and then use the pump to feed water either into the landscape irrigation system or back through one of two different fully planted side ponds which contain no fish.
Our fish load is a base of about 12 to 15 adult koi in the 20" to 30" size range and then up to about 20 yearlings which get selected from the the thousands of fry produced each year. I usually only keep one of two those yearlings each year to join the herd. |