I use two whole house filters (1 micron and then 1/2 micron carbon). They feed a whole house pressure reducer which then goes to our trailer. I got all of them at rvwaterfilters.com. The prices are fair, they assemble everything and it works very well. Since many campgrounds use less-than-great water, we find this combination gives us such good water that we no longer carry bottled water. The problems with the blue filters are that they have a pretty low flow rate which makes for disappointing showers etc. They also only filter larger particles and allow chlorine and heavy metals to pass through. The pressure regulator you buy at an RV store also has a flow problem. We were amazed by how much better everything is with the new high flow filters and regulator. If you use any "Y" connectors, be sure to get high flow too.