I just found this forum so I hope someone can advise me on my problem. I just had a new Koi pond built. It is 6ft deep 30ft wide and about 12 feet across.There is a smaller bog that flows in this bigger pond and waterfalls. I think it has about 16,000-18,000 gallons of water. There are two bottom drains going to a huge sediment chamber then two lines come out of the chamber. One goes to a 12,000 per hour pump --> waterfall, and the other line from sediment chamber --> 7,000 gallon per hour pump -->UV light then bead filter -> waterfall.

Ok heres the problem. the water level in the sediment chamber is 12 inches lower than the level in the pond. It appears that the pumps are pulling the water out of the sediment chamber faster than the water is coming to the chamber from the pond. If I turn the pumps off, the water rises in the chamber to the correct level.
As the water in the chamber falls the refill water valve comes on to replenish the "lost" water and in the course of time the level in the pond is rising. The end result is I am using an excessive amount of water and the pond is almost overflowing!

I think the main lines from the bottom drain are either clogged or just under engineered. The pond has only been up and running for about 6 weeks. I have already had the bottom drains cleared of debris once.