…has two cut-off valves. One cuts off water pressure from the main line to the filters. The other cuts off water to the whole sink and faucet assembly—apparently, and to the filters as well, since the two valves are joined for some insane reason. Meaning that if the filter line is cut off, but the faucet is running, pressure will force water through the line to the filter.
And if you’re running the faucet to clean the cups under the filter, which you have removed for this purpose and to replace the filters, the additional back pressure will push water out the top of the filter unit and flood the area under our sink.
Needless to say, this was one of the quickest (and dampest) educations in plumbing I could have gotten. The mess is cleaned up, except for whatever leaked through the bottom of the cabinet and into the unreachable floor space to feed molds and mildews, and I’m onto step three, which is cleaning out the whole system with a mild bleach solution for fifteen to twenty minutes.
Which, by my clock, is enough time to drink a beer and ignore the whole mess.