The initial 2001 Islanders came with a unique 4 stage water filtration system that filters all water coming from the fresh water tank and from outside city water. It has three filters and inside the middle stage filter is also an Infrared light that kills bacteria etc.
The unit is located in the small outside storage compartment on the passenger side just aft of the two large compartments. It is the one with the small door.
WARNING. do not attempt to change filters without first removing the entire filter unit from the mountings. You can easily turn the water to bypass mode and then loosen screws and lift the entire filter unit out. The reason for this is that one of the filters has an infrared lamp with a glass cover in the center of the filter. There is not enough clearance to take the filter off with the unit mounted and most likely you will crack the glass sleeve trying to get the filter to clear. I learned the hard way. If you have the filter unit book it should give you the address and phone numbers of the manufacturer in the Portland, OR. area. They no longer have the filters or infrared lights but can direct you to where to get them (I hope they still can).
This is a great filtering system. I know of no other Motor home with such a system. However, it does reduce water pressure a little.
Also if you have but the 30 gal. water heater, don't worry. If you put on both the electrical and propane heaters to the unit the recovery rate is such that you will not run out of hot water for a shower. If you do not have an on off switch for the water heater electrical, have one put in. Ours came without one but National easily put a switch with light at the area of the sink where the electrical outlet there is. They did it free in about 30 minutes. Should be an easy task. The wire runs along the bulkhead in that sink cabinet area.
Any questions-
topartzer@yahoo.com