All pipes are 1.5inch dia, however, Doughboy requires reducers/adapters because their equipment comes in nonstandard size (about 1.25 inch I think). The first picture shows looking down on pump- water flows left from skimmer (inlet end) through first "L" to right through pump, then at skimmer and pump. There is 52 inches through curved flex pvc from the skimmer to the 90 degree "L" on the pump . The valves are marked 1.5 inch ball valves, but there is an adapter on each end of that - the skimmer and the pump have the strange Doughboy special pipe sizes on them. The pump to the filter is about 3 feet of flex pvc that Doughboy provided and required no adapters, so I am thinking it is that same 1.25 inch size.
The second picture shows the return end with the adapter so that you can see how the reducer issue works. That is a 28 inch run down to a 90 degree "L" on the pump. The single return currently has a fountain adapter in it that is 1.5 inch OD, and the fountain adapter is a light PVC, so probably 1.25 ID. It is not currently in fountain mode, just flow through.
The next picture is working back from the return- the 58 inch horizontal run on which the flowmeter is mounted. It appears to be mounted per the requirements- we got it from plsbcheap on this site, and he was very helpful in making sure we knew what to do. The issue is that my husband will then go and do his own thing, and I was not standing over him as he mounted it, but he claims he followed the instructions.
The are 4 90 degree "L"s total and one 3-way valve in the system when the solar panels are turned off. The water flows through 1.5 inch flex pvc most of the time. The total water length flow on the return side is 29 feet with a 180 degree turn around right in the middle (where the water is bypassing the solar panels through the 3-way valve).
Complete pictures are going to have to wait until I have my good laptop back, which is currently in the shop. I am borrowing a netbook with a 9" screen- not an image editing powerhouse. To get the blow-by-aggravating-blow account of our plumbing travails- see this post
adding-solar-bear-panels-to-our-agp-the-process-with-pics-t11410.html
The plumbing had to be redone several times, so realize that the first couple of configurations shown have been reworked. I think we are on Rev D.