First the information on the new pond:
3000-4000 gallon pond
Michigan weather (0F � 100F)
About 50 medium 3-4 inch gold fish (want to add some koi maybe)
Direct sunlight � some shade from tree and house (early and late in the day)
Few plants in the pond but not many
45mil liner with Rock side and a shallow area covered in rock (dog) the deep area will be left clear liner.
Small water fall from 3600gph pump looking to add a second pump 4500gph for biofilters
Currently have (1) 55 gallon biofilter looking to add a second (parallel)

Questions:

1. What type of piping do you recommend for buried pipe? Rigid PVC or flex piping? If rigid pvc is sch 40 ok? I am looking at 2-3 inch for flow rates.

2. I am using submersible pumps. Where do you guys hide your pumps? I don�t like having the pump and hose draped across the bottom of the pond. I am looking at a savio skimmer unit with additional secondary feed line to protect the pumps (just thinking of using this to hide the pumps not so much as a filter). Can I just bury a 30 gallon drum and run 2-3 3inch pipes to it from the pond? I will put R-matala over the entrance of the savio and pipe to protect my fish and frogs.

3. Does burying the biofilter effect the bacteria efficiency? I currently have a 55 gallon drum gravity bottom to top flow biofilter made with scrubbies. The filter was partially buried because there is no place to hide it. Bio filters are not as cheap as everyone thinks A 55 gallon filter = 7.5 cuft = 192 scrubbies/cu ft with 6 scrubbies for $1 the 55 gallons = $236 just for media.

4. What does everyone use for bulkheads to the side of the drums (for bottom valves). I have to come off the sides of the drums for the bottom valve (this allows me to bury the 55gal drums and still flush).

5. What does everyone use for pipe penetrations into the liner.

6. What pond foam do you recommend? I am putting rocks along the perimeter vertical wall 24inches (to keep dog off the liner). I will need to lock the rocks in place so if he climbs them they don�t move.

2. I have a pump hidden inside the skimmer and another at the last phase of my chain of filter tubs, which will draw from the BD. As Joe 09 mention, an external pump is an excellent choice. They are expensive, but I'm told they are more energy efficient.

3. I know of no reason why burying the biofilter would affect the efficiency of the bacteria. Just make sure you have a suitable method of cleaning, such as being able to lift the bio bags to rinse in a separate tub of pond water. Most people have them above ground, though, so they can simply aggitate the media and then open a valve to drain.

4 & 5 ??

6. I just use waterfall foam purchased at Lowes or Home Depot. I've tried cheaper varieties, but for some reason they didn't set up properly.

You have to use regular bulkheads for the liner. There are a variety listed in the same link.