I have been using the WW switches for about 12 years now. No failures. No issues. All of my centrifugal pumps would be considered "crash" pumps by most folks, as they all have 1&1/2 inch outlets and are plumbed to thru hulls that are mounted as high as practical. My "dewatering" pumps are the belt driven diaphram type. They are easily repairable and mine are all the same, 1 inch outlet pumps so I keep a complete spare and lots of parts. They are fairly expensive. The best thing about the WW switch is the over run feature, it allows the diaphram pump to run awhile after the switch has no water on it. These pumps can remove just about all of the bilge water, unlike the centrifugals which by design cannot, then you get the hose water run back also. All of my diaphram pumps pull thru perko raw water strainers to help keep the big chunks out of the pump. All of the switches are wired to a pair of 30 amp relays so the switch itself doesnt carry the pump load. I use a pair of relays for redundancy, 1 would work fine. I have not had any issues with oil stopping the float from working, even with oil in the bilge. It doesnt seam to "coat" the contacts and prevent them from working. The switch just wont turn on until it gets water on the contacts (under the oil) then it turns off when the water is not on the contacts (oil still there). The over run will cause your pump to pump the oil until it times out. Sometimes that is not desirable.