Norm, you do have a home style accumulator tank. Check to see if it is full of water. Tap on tank with hand, if you get hollow sound, it is good. If it sounds solid, it is full of water, and needs to be changed. As far as the filter you talk about, if it is on suction side of pump, it is a water strainer to prevent debris from entering pump. If on pressure side, it is a water filter with replaceable cartridges in it. I have seen this setup on Monaco Signature Motorhomes. By doing a little research on these items, you should be able to figure out what you need, and what needs to be addressed. Hope this helps.