Its been a long day, almost 9pm and I just got home about 30 min ago. I don't have an exact parts list, but it's pretty straight forward. I'll post pictures and exact parts when I build it. But for now I'll try to explain what I plan. First there are really only two main parts to it, the canisters (filter housing), and the filters. The filter housings unscrew, and the filter is placed inside. The filter housings are basically standard sizes (like the 2.5 x 10 Inch I'll be using), and the filters are made to fit the housings. Here are two that they have at Home Depot and Lowe's.
Household Water Filtration Unit-GXWH04F at The Home Depot
Shop Whirlpool Opaque Whole-House Pre-Filtration Housing at Lowes.com
I'll most likely be using these filter housings from home depot because their about 2 bucks cheaper, $17.98 verse $20 at Lowe's (they use the same 2.5 x 10 filters). Some will have a clear canister's that allows you to view the filter insides. Those are particularly good for pre-sediment filters, because you can physically see when they are getting clogged/dirty. These filter housings are designed to mount underneath your counter, or on a wall, and usually come with a mounting bracket.
The top part of the housing mounts to the wall, and the bottom part unscrews. If you look closely at the picture of the filter housing, you'll see a threaded opening on the top part of the housing. There's one of these threaded opening on both sides of the top part of the filter housing. These threaded openings fit standard pluming threads. You can use either a standard flexible faucet hose, or a threaded PVC adapter. Then connect it to a flexible hose to PVC tubing. One side of the filter will be the "IN" side (water inlet from your source water) and/or from a water faucet. The other side will be your filtered water, the "OUT" side.
To create a custom filtration system, just place more than one of these filter housings in series. In my case I'll be using 4 to 5 filter housings in series (like in the image). Four filter housings at $18 ea, will run $72 (5x $18=$90), then I'll need a few short flexible faucet hoses, as well as threaded PVC adapters (some Teflon tape to seal the threads), that will probably run $10 to $20. Then I have the water system built (well besides the wood, or composite wood frame I'll need to mount it to).
Now I just need the replaceable filters to put in the filter housings. After all that's what's going to filter the water. I know the basic filters I'll want, but I will be talking to some professionals to make sure I get the best filters for my needs. The filters come in standard sizes to fit the housing (like 2.5 inch x 10 inch filter housings), but come in an array of types of filters, as well as wide range in prices. Pre-filters are sediment filters, and are first. Their for catching the large particles that will clog the other filters faster.
String Wound Water Sediment Filter Cartridge $2.99 (typical sediment filter)
3M Aqua-Pure AP110 Water Sediment Filter Alternative $4.99 (NOTE: this filter cartridge contains two distinct micron layers)
Lead Removal Solid Activated Carbon Block Water Filter Cartridge $12.95 (Typical Activated Carbon filter)
BEST - 2.5 x 10 inch Activated Carbon Block Water Filter $17.95
More similar cartridges
Carbon Block Cartridges
Beer and Wine Filtration
Carbon Block Cartridges
Discount Water Filters, Cartridges and Drinking Water Systems
That's from just one company selling water filter cartridges online, there are a lot of them. And here in our town/city there are company's that specialize in water filtration that sell them as well. And who I will be talking to about the best filters to use (they know our water well).